17:I[462708,["/_next/static/chunks/3yo3kiro3bmlp.js","/_next/static/chunks/3vr2wvd8f2efb.js","/_next/static/chunks/2vtmb68_vu-9t.js","/_next/static/chunks/2s8mt6_8wrpfo.js","/_next/static/chunks/3vkulz2i3l61y.js","/_next/static/chunks/1cqw2i1silz0i.js","/_next/static/chunks/14dbm3lm_t629.js","/_next/static/chunks/335_v2mb569ld.js","/_next/static/chunks/1jvnwmb7jnkpz.js","/_next/static/chunks/3cmavum774kjt.js","/_next/static/chunks/3th-0-a2xf9qs.js","/_next/static/chunks/0p0xpwde6kzmv.js","/_next/static/chunks/401-sxxnzbtf_.js","/_next/static/chunks/0wywtv698a1v0.js","/_next/static/chunks/2botzqwpnrzyj.js"],"ArticleReader"] 18:Tc5b9,## One-minute summary **Acute pulmonary embolism (PE)** is obstruction of the pulmonary arterial circulation by thrombus, usually arising from deep veins of the legs or pelvis. The immediate threat is **acute right-ventricular (RV) pressure overload**, which may progress from compensated RV strain to reduced left-ventricular preload, systemic hypotension, obstructive shock, and cardiac arrest. The 2026 multisociety AHA/ACC guideline introduces a new **A–E Acute PE Clinical Category system** that moves beyond the older low/intermediate/high-risk labels. [1,3] - **A:** incidental/asymptomatic PE. - **B:** symptomatic PE with a low clinical severity score. - **C:** symptomatic PE with an elevated clinical severity score, stratified by RV dysfunction and cardiac biomarkers. - **D:** incipient cardiopulmonary failure, such as transient hypotension or normotensive shock/end-organ hypoperfusion. - **E:** established cardiopulmonary failure, including persistent hypotension with shock or cardiac arrest. [1,3] The core clinical pathway is: **Estimate pretest probability → use PERC only in truly very-low-risk patients → use D-dimer when appropriate → CTPA (or V/Q when needed) → confirm PE → immediately risk-stratify → anticoagulate unless contraindicated → identify who is safe for outpatient care vs who needs monitored hospitalization or advanced reperfusion.** High-yield 2026 practice points: [1] - A negative **age-adjusted D-dimer** can avoid imaging in appropriate low/intermediate-probability patients over age 50. - **CTPA** is the usual first-line definitive test; V/Q scanning is valuable when iodinated contrast is unsuitable. - **LMWH is preferred over UFH** when initial parenteral anticoagulation is required in most C1–E1 patients. - **DOACs are preferred over vitamin K antagonists** for most eligible adults. - Advanced reperfusion therapies are **reasonable in Category E1** and may be considered in **D1–D2**; routine systemic thrombolysis is harmful in A–C2. - **PERT assessment is recommended** for higher-risk categories to improve care delivery. - Follow-up should include anticoagulation review and screening for persistent dyspnea/functional limitation and chronic thromboembolic pulmonary disease (CTEPD). Two major randomized trials published after the guideline evidence cutoff—**HI-PEITHO** and **PRAGUE-26**—showed fewer early clinical deterioration events with catheter-directed thrombolysis in selected intermediate-risk/intermediate-high-risk patients. These are important **emerging evidence**, but they do not yet justify indiscriminate catheter treatment of all normotensive PE. [15,16] --- ## 1. Definition and core concepts ### 1.1 Definition Acute PE is partial or complete obstruction of one or more pulmonary arteries by embolic material, overwhelmingly thrombus. Most thrombi originate from lower-extremity or pelvic deep venous thrombosis (DVT), although upper-extremity catheter-associated thrombosis and other sources occur. #### Anatomical terms - **Subsegmental PE:** clot limited to subsegmental pulmonary arteries. - **Segmental PE:** segmental branch involvement. - **Lobar/proximal PE:** lobar or main pulmonary artery involvement. - **Saddle PE:** thrombus straddling the pulmonary artery bifurcation. This is an anatomical description, **not a severity category**; a saddle embolus can be hemodynamically stable, while a smaller clot burden can be fatal in a patient with limited cardiopulmonary reserve. ### 1.2 The main physiological problem is RV afterload Abrupt obstruction plus vasoconstriction increases pulmonary vascular resistance. The RV, a thin-walled chamber adapted to a low-pressure system, dilates under acute pressure load. RV wall tension and oxygen demand rise while coronary perfusion can fall. The interventricular septum shifts toward the LV, impairing LV filling. Cardiac output declines; systemic hypotension further reduces RV coronary perfusion, creating a vicious cycle. #### Hemodynamic spiral ```text Pulmonary arterial obstruction ↓ ↑ Pulmonary vascular resistance ↓ RV dilation + ↑ wall stress ↓ Tricuspid regurgitation + septal shift ↓ ↓ LV preload and cardiac output ↓ Hypotension / systemic hypoperfusion ↓ ↓ RV coronary perfusion ↓ RV ischemia → worsening RV failure ↓ Obstructive shock / cardiac arrest ``` This explains why **blood pressure alone is insufficient** for risk assessment: a patient may be normotensive while already developing low cardiac output, lactate elevation, acute kidney injury, oliguria, or altered mental status. --- ## 2. Epidemiology and risk factors PE is a major manifestation of venous thromboembolism (VTE). Risk follows **Virchow’s triad**: venous stasis, endothelial injury, and hypercoagulability. ### 2.1 Major provoking factors #### Strong transient factors - Major surgery, especially orthopedic/pelvic surgery - Major trauma or fracture - Prolonged hospitalization or severe acute illness - Marked immobilization - Pregnancy and postpartum state #### Persistent factors - Active cancer - Chronic inflammatory or autoimmune disease - Persistent immobility - Antiphospholipid syndrome (APS) - Selected inherited thrombophilias #### Common acquired risk factors - Prior VTE - Increasing age - Obesity - Estrogen-containing hormonal therapy - Heart failure - Chronic lung disease - Nephrotic syndrome - Central venous catheters - Myeloproliferative neoplasms ### 2.2 Provoked vs unprovoked is clinically useful—but imperfect The traditional binary distinction helps estimate recurrence risk, but risk is a continuum. A PE after major surgery is very different from a PE after a minor transient trigger in a patient with obesity, inflammatory disease, and previous VTE. Modern duration decisions increasingly incorporate **persistent risk, recurrence risk, bleeding risk, and patient preference**, rather than relying on a single label. [1,17] --- ## 3. Clinical presentation PE ranges from asymptomatic incidental imaging findings to sudden cardiac arrest. ### 3.1 Common symptoms - Acute or progressive dyspnea - Pleuritic chest pain - Nonpleuritic chest pressure - Cough - Hemoptysis - Syncope or presyncope - Palpitations - Unilateral leg pain/swelling ### 3.2 Common signs - Tachycardia - Tachypnea - Hypoxemia - Fever (usually low grade if present) - Unilateral leg swelling/tenderness - Elevated JVP - RV heave - Loud P2 - New tricuspid regurgitation murmur - Hypotension, cool extremities, altered mental status, oliguria in advanced disease ### 3.3 Red flags for impending deterioration - Syncope with persistent tachycardia or borderline BP - SBP near 90–110 mm Hg or a meaningful fall from baseline - Rising lactate - Increasing oxygen requirement - RR ≥30/min - New confusion - Oliguria/acute kidney injury - Marked RV dilation or reduced RV function - Elevated troponin with RV dysfunction - Free-floating right-heart clot-in-transit A normotensive patient with several of these features may be in **incipient cardiopulmonary failure**, not “stable PE.” [1] --- ## 4. Differential diagnosis | Condition | Features that overlap | Clues favoring alternative diagnosis | |---|---|---| | Acute coronary syndrome | Chest pain, dyspnea, troponin elevation | Ischemic ECG pattern/coronary syndrome; remember PE can also elevate troponin | | Pneumonia | Dyspnea, pleuritic pain, fever, hypoxemia | Focal infiltrate, infectious prodrome; PE and pneumonia can coexist | | Pneumothorax | Sudden dyspnea/pleuritic pain | Unilateral absent breath sounds, pleural line on ultrasound, CXR findings | | Acute aortic syndrome | Chest/back pain, syncope | Pulse/BP differential, aortic imaging findings | | Acute heart failure | Dyspnea, hypoxemia, elevated BNP | Pulmonary edema, LV dysfunction; PE can precipitate RV-predominant failure | | Pericarditis | Pleuritic pain | Positional pain, diffuse ST elevation/PR depression | | COPD/asthma exacerbation | Dyspnea, tachycardia | Wheeze/known disease; PE remains possible if unexplained deterioration | | Panic/hyperventilation | Dyspnea, chest discomfort | Diagnosis of exclusion when PE probability is nontrivial | | Sepsis | Tachycardia, hypotension, lactate elevation | Infection source; PE can coexist with systemic illness | --- ## 5. Diagnostic strategy: probability before testing The biggest diagnostic error is ordering tests without first considering **pretest probability**. D-dimer is useful when disease probability is low enough that a negative result safely rules out PE; it is inefficient in high-probability patients and frequently positive in hospitalized, elderly, pregnant, inflammatory, postoperative, and cancer populations. ### 5.1 Step 1 — Is the patient unstable? If the patient has shock or cardiac arrest and PE is strongly suspected: - Resuscitate immediately. - Obtain bedside echocardiography/POCUS if it can be performed without delaying treatment. - Obtain CTPA if the patient can safely reach CT. - Activate PERT/critical care/interventional/surgical resources early. Echocardiography is **not recommended to confirm or exclude PE in a stable suspected case**, because RV findings are not sufficiently specific; its major value is risk stratification and bedside assessment in unstable patients. [1] ### 5.2 Step 2 — Estimate clinical probability Validated tools include: - Wells score - Revised Geneva score - Clinical gestalt in experienced hands The practical purpose is to classify the patient into a pathway where PE is: - very unlikely, - low/intermediate probability, or - high probability. ### 5.3 PERC — only for very-low-risk patients The **Pulmonary Embolism Rule-out Criteria (PERC)** may allow no further testing when clinician-estimated pretest probability is very low (commonly <15%) and **all 8 criteria are absent**: 1. Age ≥50 years 2. Pulse ≥100/min 3. SpO₂ <95% 4. Unilateral leg swelling 5. Hemoptysis 6. Estrogen use 7. Prior DVT/PE 8. Recent surgery or trauma requiring hospitalization If any PERC criterion is positive, PERC does not rule out PE—move to a D-dimer or imaging strategy depending on pretest probability. [1] **Pitfall:** PERC is not a “PE score” to apply indiscriminately to every patient with chest pain. ### 5.4 D-dimer #### Standard threshold A highly sensitive D-dimer below the assay cutoff (often 500 µg/L FEU) excludes PE in appropriately selected low/intermediate-probability patients. #### Age-adjusted D-dimer For patients older than 50 years, a commonly validated threshold is: **Age × 10 µg/L FEU** Example: age 72 → negative threshold <720 µg/L FEU, assuming the assay uses compatible FEU units. [1,5] Always confirm laboratory units and assay convention; D-dimer units are not interchangeable. ### 5.5 YEARS strategy The YEARS algorithm assesses three items: - Clinical signs of DVT - Hemoptysis - PE judged the most likely diagnosis Typical thresholds: [6] - **No YEARS items:** D-dimer <1000 µg/L FEU can exclude PE. - **≥1 YEARS item:** D-dimer <500 µg/L FEU can exclude PE. A pregnancy-adapted YEARS pathway is an evidence-based option in selected pregnant patients and can reduce unnecessary chest imaging when applied correctly. [1] --- ## 6. Imaging and bedside tests ### 6.1 CTPA **CT pulmonary angiography (CTPA)** is the standard definitive imaging test in most adults. It provides: - direct visualization of emboli; - clot location/burden; - alternative diagnoses; - RV/LV ratio for risk stratification; - signs of chronic thromboembolic disease. The 2026 guideline recommends **numerical RV/LV ratio reporting** rather than subjective RV enlargement when CTPA is performed. [1] ### 6.2 Ventilation-perfusion (V/Q) scanning V/Q scanning is especially useful when: - iodinated contrast is contraindicated; - severe contrast allergy exists; - renal function makes CTPA undesirable in the individual context; - radiation distribution is a concern, including selected pregnancy pathways; - chest radiograph is relatively normal, improving interpretability. ### 6.3 Compression ultrasonography Finding a proximal DVT can establish VTE and may support treatment when chest imaging is impossible or undesirable, but a negative leg ultrasound does **not** exclude PE. ### 6.4 Echocardiography In confirmed PE, echo assists risk assessment by evaluating RV size/function and pulmonary pressures. The August 11, 2026 correction to the AHA/ACC guideline clarified right-heart echocardiographic parameters. [2] | Parameter | Abnormal / concerning threshold or finding | |---|---| | RV/LV end-diastolic ratio | >0.9 abnormal in the guideline framework | | RV end-diastolic dimension | ≥30 mm in an RV-focused parasternal long-axis view, or basal RV EDD ≥41 mm in an apical RV-focused view | | TAPSE | ≤1.7 cm abnormal | | TDI S′ velocity | ≤9.5 cm/s abnormal | | TR velocity | ≥2.9 m/s suggests pulmonary hypertension | | Other findings | McConnell sign, paradoxical septal motion, reduced IVC respirophasic collapse, elevated estimated RV systolic pressure | No single echo sign proves PE; interpret the overall pattern and clinical context. ### 6.5 ECG Possible findings: - Sinus tachycardia (most common) - Right bundle-branch block - Right-axis deviation - Anterior T-wave inversion - S1Q3T3 pattern - Atrial arrhythmias **S1Q3T3 is neither sensitive nor specific** and should never be used to rule in or rule out PE. ### 6.6 Laboratory biomarkers #### Troponin Elevation reflects RV myocardial injury and is prognostic in confirmed PE; it is not specific for PE. #### BNP/NT-proBNP Reflects RV wall stress and helps risk stratification. #### Lactate Elevated lactate can reveal low-output physiology/end-organ hypoperfusion despite preserved blood pressure. In the 2026 framework it is important for identifying **normotensive shock / Category D2 physiology**. [1,3] --- ## 7. 2026 AHA/ACC Acute PE Clinical Categories The new classification is designed to connect bedside severity directly to disposition and therapy. [1,3] | Category | Clinical picture | Key objective features | Typical disposition/implication | |---|---|---|---| | **A** | Subclinical/incidental, asymptomatic PE | No PE symptoms | Usually outpatient if no separate reason for admission | | **B** | Symptomatic, low clinical severity | Low PESI/sPESI/Hestia profile | Early discharge/outpatient treatment often appropriate | | **C1** | Symptomatic, elevated clinical severity | Normal RV and normal cardiac biomarkers | Hospitalization; anticoagulation | | **C2** | Symptomatic, elevated severity | RV abnormality **or** ≥1 abnormal cardiac biomarker | Hospitalization; closer monitoring | | **C3** | Symptomatic, elevated severity | RV abnormality **and** ≥1 abnormal cardiac biomarker | Higher deterioration risk; monitored care/PERT consideration | | **D1** | Incipient cardiopulmonary failure | Transient/recurrent hypotension or relative hypotension without established end-organ hypoperfusion | High-acuity monitored care; advanced therapy may be considered | | **D2** | Incipient failure with hypoperfusion | Transient/relative hypotension plus end-organ hypoperfusion such as lactate >2 mmol/L, AKI, oliguria, mental-status change, low cardiac index/MAP | Critical-care level; PERT; advanced reperfusion consideration | | **E1** | Cardiopulmonary failure | Persistent/recurrent hypotension with cardiogenic shock | Advanced therapy is generally reasonable if feasible | | **E2** | Refractory failure / arrest | Refractory shock or cardiac arrest | Resuscitation, systemic lysis when appropriate, ECMO/advanced rescue in expert centers | #### Respiratory modifier “R” The 2026 system adds an **R modifier** when significant respiratory compromise is present. In Category C this includes features such as SpO₂ <90%, RR ≥30/min, or supplemental oxygen requirement; more advanced categories use higher oxygen/ventilatory support thresholds. [1,3] #### Why this is better than “massive/submassive” The older terminology can hide important gradients. A normotensive patient with RV dysfunction, positive troponin, lactate 4 mmol/L, oliguria, and escalating oxygen needs is much sicker than another normotensive patient with mild RV dilation alone. The A–E framework explicitly identifies that difference. --- ## 8. PESI, sPESI, and Hestia ### 8.1 PESI/sPESI These scores estimate short-term mortality and are most helpful when considering outpatient management. A **sPESI of 0** identifies a low-risk group when other outpatient criteria are satisfied. ### 8.2 Hestia criteria Hestia is a pragmatic exclusion checklist for outpatient treatment, incorporating hemodynamic instability, oxygen requirement, bleeding risk, severe pain needing IV medication, renal/liver failure, pregnancy, social barriers, and other practical concerns. **Important:** A low PESI/sPESI does not override clinical judgment, RV dysfunction, active bleeding, inability to obtain medication, severe comorbidity, or inadequate follow-up. --- ## 9. Acute management algorithm ```text Suspected PE ↓ Is patient in shock / peri-arrest? ├─ Yes → ABC resuscitation + bedside echo if useful + urgent CTPA if feasible │ → therapeutic anticoagulation if not contraindicated │ → PERT / ICU / interventional / surgical activation │ → consider immediate reperfusion strategy └─ No ↓ Estimate pretest probability ↓ Very low risk + all PERC negative? ├─ Yes → PE ruled out without D-dimer └─ No ↓ Low/intermediate probability → D-dimer strategy ├─ Negative → PE excluded └─ Positive → CTPA (or V/Q) High probability → proceed directly to imaging ↓ PE confirmed ↓ Anticoagulate unless contraindicated ↓ Risk stratify: PESI/sPESI/Hestia + RV + troponin/BNP + lactate + BP/perfusion + oxygen ↓ A/B → outpatient/early discharge when safe C → hospitalize; monitor intensity by C1/C2/C3 + R D → critical/step-down care + PERT; consider advanced reperfusion E → shock/arrest pathway; advanced reperfusion ± VA-ECMO in expert center ``` --- ## 10. Anticoagulation — STANDARD OF CARE Unless there is an absolute contraindication, **therapeutic anticoagulation should be initiated for acute PE** to reduce recurrence and death. [1] ### 10.1 Initial parenteral anticoagulation When parenteral therapy is required, the 2026 guideline recommends **LMWH over UFH** for most patients in Categories C1–E1 because LMWH reduces recurrent VTE and major bleeding. [1] #### When UFH can still be advantageous UFH is often selected when: - an immediate invasive procedure or thrombolysis is likely and rapid titration/reversal is desired; - severe renal dysfunction limits LMWH use; - extremely unstable physiology requires a highly controllable infusion; - local advanced-therapy protocols specify UFH. Do not treat “UFH for every high-risk PE” as a universal rule; the 2026 guideline explicitly prefers LMWH when parenteral therapy is required in most eligible patients. [1] ### 10.2 DOACs For eligible adults, **DOACs are recommended over vitamin K antagonists**. [1] Common evidence-based VTE regimens: [4] | Drug | Initial phase | Primary treatment | |---|---|---| | **Apixaban** | 10 mg PO twice daily for 7 days | 5 mg PO twice daily | | **Rivaroxaban** | 15 mg PO twice daily with food for 21 days | 20 mg PO once daily with food | | **Dabigatran** | Requires ≥5 days of parenteral anticoagulation first | 150 mg PO twice daily | | **Edoxaban** | Requires ≥5 days of parenteral anticoagulation first | 60 mg PO once daily in standard eligible patients | **Safety note:** renal function, hepatic function, age, weight, drug interactions, bleeding risk, and product-specific labeling must be checked before prescribing. Edoxaban and other agents have label-defined dose modifications that should not be guessed from memory. #### 2026 comparative evidence The COBRRA randomized trial compared apixaban with rivaroxaban for acute VTE and found clinically relevant bleeding at 3 months in **3.3% vs 7.1%**, respectively, with similar VTE efficacy. The 2026 ACC scientific statement therefore suggests apixaban may be preferred for many patients when either agent is otherwise suitable. This is an evolving comparative-practice consideration rather than a declaration that rivaroxaban is inappropriate. [4,18] ### 10.3 Empiric anticoagulation before imaging If PE is strongly suspected, imaging is delayed, and bleeding risk is low, the 2026 guideline states that therapeutic anticoagulation may be beneficial in patients with a clinical picture equivalent to **Category C2 or higher**. [1] This is not an excuse to anticoagulate every low-probability patient before diagnosis. --- ## 11. Reperfusion and advanced therapies The central decision is whether anticoagulation alone is sufficient or whether clot removal/lysis is needed because the RV is failing or likely to fail. ### 11.1 Systemic thrombolysis #### Standard regimen The most commonly used FDA-approved alteplase regimen for PE is: **Alteplase 100 mg IV over 2 hours.** [1] Lower-dose systemic regimens may be considered in selected circumstances to reduce bleeding, but evidence is less robust and protocols vary. [1] #### Who should receive systemic thrombolysis? | 2026 category | Systemic lysis position | |---|---| | A–C1 | **Harm / do not use routinely** | | C2 | **Harm / do not use routinely** | | C3 | Benefit uncertain; highly individualized if advanced therapy is contemplated | | D1–D2 | May be considered with acceptable bleeding risk | | E1–E2 | Reasonable when advanced reperfusion is indicated and bleeding risk is acceptable | This explains a classic board principle: **routine fibrinolysis for a normotensive intermediate-risk PE is not standard care**. The PEITHO trial reduced hemodynamic decompensation but increased major extracranial bleeding and hemorrhagic stroke with systemic tenecteplase, without a mortality advantage sufficient to justify routine use. [7] ### 11.2 Catheter-directed thrombolysis (CDT) The 2026 guideline position, based largely on pre-2025 evidence, is: [1,3] - **E1:** CDT + anticoagulation is reasonable. - **D1–D2:** may be considered when advanced therapy is being considered. - **C2–C3:** benefit vs anticoagulation alone was considered uncertain. - **A–C1:** routine catheter intervention has no benefit. This field changed materially after the evidence cutoff; see HI-PEITHO and PRAGUE-26 below. ### 11.3 Mechanical thrombectomy For catheter-based mechanical thrombectomy (MT): [1] - **E1:** reasonable compared with anticoagulation alone. - **D1–D2:** may be considered. - **C2–C3:** benefit remains uncertain for routine use. - A–C1: not routinely beneficial. A major attraction is avoiding or minimizing thrombolytic exposure, but access-site bleeding, pulmonary-artery injury, blood loss, procedural deterioration, and device-specific complications remain possible. ### 11.4 Surgical embolectomy Surgical embolectomy is reasonable in **E1** and may be considered in selected **D1–D2** patients, especially when thrombolysis is contraindicated or has failed and surgical expertise is immediately available. [1] It can also be attractive for: - central clot burden with shock; - right-heart clot-in-transit; - selected patients with a patent foramen ovale and systemic embolic risk; - situations where catheter options are unsuitable. ### 11.5 Right-heart clot-in-transit A free-floating right-atrial/RV thrombus is uncommon but high risk. In Categories C3–E2, the 2026 guideline considers advanced therapy reasonable over anticoagulation alone to reduce deterioration, although randomized comparative evidence is limited. [1] ### 11.6 VA-ECMO **Venoarterial extracorporeal membrane oxygenation (VA-ECMO)** can provide circulatory/oxygenation support in refractory cardiogenic shock or arrest from PE in expert centers. It is usually a bridge to recovery or definitive reperfusion, not treatment of the clot itself. [1] --- ## 12. Hemodynamic and respiratory support ### 12.1 Oxygen and ventilation Correct hypoxemia while avoiding interventions that precipitate RV collapse. Positive-pressure ventilation can reduce venous return and increase RV afterload. In a tenuous PE patient, deep sedation and intubation may trigger sudden cardiovascular collapse. If intubation is unavoidable: - involve experienced airway/critical-care staff; - optimize preload and vasopressor support before induction; - use hemodynamically cautious induction; - minimize excessive PEEP/airway pressures while maintaining adequate oxygenation. ### 12.2 Fluids The failing RV is preload-sensitive but easily overdistended. Large indiscriminate fluid boluses can worsen septal shift and cardiac output. Use **small, reassessed fluid challenges** only when true preload deficiency is plausible. Stop if JVP/RV dilation worsens without improved perfusion. ### 12.3 Vasopressors/inotropes In obstructive shock, vasopressor support is often required to restore systemic pressure and RV coronary perfusion while definitive reperfusion is arranged. Norepinephrine is commonly favored in shock physiology; inotropes may be added for severe low-output RV failure under critical-care guidance. The goal is not simply a numeric blood pressure—it is restoration of **organ perfusion** without excessive tachycardia or RV oxygen demand. --- ## 13. Disposition ### Category A The 2026 guideline states that asymptomatic Category A patients can generally be discharged rather than hospitalized, assuming no competing reason for admission and a safe treatment/follow-up plan. [1,3] ### Category B Early discharge/outpatient treatment is generally recommended if: - low PESI/sPESI/Hestia risk; - no oxygen/hemodynamic instability; - no major bleeding risk; - reliable access to anticoagulation; - adequate home support and follow-up. ### Categories C–E Hospitalization is recommended because of increasing deterioration risk. Level of care escalates with: - C3 physiology; - respiratory modifier; - lactate/end-organ hypoperfusion; - transient hypotension; - escalating oxygen; - shock/arrest. --- ## 14. Duration of anticoagulation The 2026 guideline defines: - **Initial treatment phase:** first **3–6 months**. - **Extended phase:** beyond 6 months. [1] ### 14.1 Major reversible provoking factor If a first PE occurred because of a **major reversible risk factor** and that factor has resolved, stopping anticoagulation after the initial treatment phase is generally recommended when recurrence risk is low and there is no other indication for continued therapy. [1] ### 14.2 No major reversible factor / unprovoked PE Extended anticoagulation is recommended for many patients after a first PE without a major reversible risk factor, assuming bleeding risk is acceptable. [1] ### 14.3 Persistent risk factor Continued anticoagulation is generally recommended while a clinically important persistent risk factor remains, with periodic reassessment. ### 14.4 Extended-dose options Evidence-supported extended regimens include: [4] - **Apixaban 2.5 mg twice daily** after completion of primary therapy in selected patients. - **Rivaroxaban 10 mg once daily** in selected patients. - Full-dose regimens remain appropriate in patients with higher recurrence risk. Duration is a shared decision balancing recurrence risk, bleeding risk, comorbidity, preference, cost, adherence, and changing life circumstances. --- ## 15. Special populations ### 15.1 Pregnancy Pregnancy changes both diagnostic and treatment decisions. - Pregnancy-adapted YEARS can reduce imaging in appropriate patients. - **LMWH is generally preferred** for treatment during pregnancy. - UFH may be useful close to delivery or when rapid reversibility is needed. - DOACs should not be used routinely in pregnancy and are generally avoided during breastfeeding because of insufficient safety data. - Warfarin is teratogenic and is generally avoided during pregnancy, although there are narrow specialist-managed exceptions in mechanical-valve care unrelated to routine PE treatment. A pregnant patient with shock from PE requires immediate multidisciplinary maternal resuscitation; maternal survival is the priority. ### 15.2 Cancer-associated PE DOACs or LMWH are effective. Choice depends on: - bleeding risk, particularly GI/GU mucosal tumors; - thrombocytopenia; - drug interactions; - vomiting/malabsorption; - renal function; - planned procedures; - patient preference. The 2026 ACC statement notes a strong evidence base for apixaban in cancer-associated thrombosis, while LMWH remains valuable in high-bleeding-risk or interaction-heavy situations. [4] ### 15.3 Antiphospholipid syndrome For thrombotic APS—especially high-risk/triple-positive APS—**vitamin K antagonist therapy is generally preferred over DOACs** because DOACs have been associated with excess recurrent arterial/thrombotic events in high-risk APS. ### 15.4 Severe renal disease Renal clearance differs substantially among DOACs. Severe CKD/dialysis requires drug-specific labeling and specialist judgment; do not apply standard VTE doses automatically. UFH or carefully selected anticoagulant strategies may be preferable in some patients. ### 15.5 Liver disease Hepatic dysfunction affects both coagulation and DOAC metabolism. The 2026 ACC statement supports individualized use by Child-Pugh class and notes that evidence becomes very limited in severe hepatic disease. [4] ### 15.6 Isolated subsegmental PE Management is individualized. Important questions include: - Is the diagnosis radiographically certain? - Is there proximal DVT? - Is the patient pregnant, has active cancer, prior VTE, impaired cardiopulmonary reserve, or persistent provoking risk? - Is the patient symptomatic? - Can reliable surveillance be performed? Selected low-risk patients with isolated subsegmental PE and no DVT may be candidates for surveillance in some guidelines, but many patients have enough recurrence risk to favor anticoagulation. This requires careful shared decision-making rather than an automatic rule. [17] --- ## 16. Complications | Complication | Clinical clues | Management principle | |---|---|---| | Obstructive shock | Hypotension, cool skin, oliguria, lactate rise, confusion | Vasopressor support + urgent reperfusion strategy | | Cardiac arrest | Often PEA | CPR + high suspicion; systemic lysis/ECMO/advanced reperfusion as appropriate | | Recurrent PE | New dyspnea/chest pain/syncope while treated | Verify adherence/dose/interactions; repeat imaging; consider alternate anticoagulant class | | Major bleeding | GI, intracranial, retroperitoneal, access-site | Stop/reverse anticoagulation as appropriate; hemostasis; reassess thrombosis risk | | Chronic thromboembolic pulmonary disease | Persistent dyspnea/exercise intolerance ≥3 months | Structured evaluation; V/Q often central to CTEPD workup; refer expert center | | CTEPH | Persistent pulmonary hypertension from chronic organized thrombi | Expert-center evaluation for endarterectomy/BPA/medical therapy | | Post-PE syndrome | Dyspnea, reduced exercise capacity despite no CTEPH | Exclude CTEPD, cardiac/pulmonary disease; rehabilitation and targeted management | --- ## 17. Follow-up after acute PE The acute event is not over at discharge. The 2026 guideline recommends: [1,3] - early post-discharge contact/assessment can be helpful, often within the first week; - a clinical visit **by about 3 months** to assess symptoms, bleeding, adherence, provoking factors, and anticoagulation duration; - asking about **dyspnea and functional limitation for at least 1 year** after PE; - evaluating persistent symptoms after ≥3 months of anticoagulation for CTEPD/CTEPH or other causes. #### Follow-up checklist - Confirm anticoagulant and correct dose. - Check renal/hepatic function when relevant. - Review bleeding and interacting medications. - Clarify whether the PE was major-provoked, minor-provoked, persistent-risk, or unprovoked. - Decide initial vs extended anticoagulation plan. - Encourage safe early ambulation. - Review cancer screening based on age/standard indications rather than indiscriminate extensive testing. - Ask about exertional dyspnea, exercise intolerance, chest pain, syncope, edema. --- ## 18. Common pitfalls | Pitfall | Why it is dangerous | Better approach | |---|---|---| | Ordering D-dimer in a high-probability patient | Delays definitive imaging and is likely positive | Proceed directly to imaging | | Using PERC in moderate-risk patients | PERC was designed for very-low pretest probability | Estimate probability first | | Treating saddle location as synonymous with “massive PE” | Anatomy ≠ physiology | Risk-stratify by BP, perfusion, RV function, biomarkers, respiratory status | | Calling a normotensive patient “stable” despite lactate/AKI | Misses normotensive shock | Assess end-organ perfusion and Category D physiology | | Giving liters of crystalloid for RV shock | Can overdistend RV and reduce LV filling | Small, reassessed bolus only if preload-responsive; vasopressors/reperfusion early | | Intubating a tenuous PE patient without hemodynamic preparation | Induction/positive pressure can precipitate arrest | Optimize pressors/preload; expert airway strategy | | Routine systemic lysis in intermediate-risk PE | Major bleeding/ICH risk | Anticoagulation + monitoring; select advanced therapy by deterioration risk | | Assuming all catheter devices have equal RCT evidence | Devices/mechanisms differ | Apply trial data only to comparable technology/populations | | Stopping anticoagulation automatically at 3 months | Recurrence risk may remain high | Reassess provoking/persistent factors and bleeding risk | | Ignoring persistent dyspnea after PE | Misses CTEPD/CTEPH | Structured follow-up for at least a year | --- ## 19. Acute management checklist ### First 10–30 minutes - [ ] ABC assessment; identify shock/arrest. - [ ] Oxygen as needed; avoid unplanned deep sedation/intubation in RV failure. - [ ] IV access, ECG, continuous monitoring. - [ ] Determine pretest probability if diagnosis is not established. - [ ] PERC only if truly very low risk. - [ ] D-dimer if low/intermediate probability and appropriate. - [ ] CTPA or V/Q when indicated. - [ ] If confirmed: assess BP trend, oxygen requirement, RV, troponin/BNP, lactate, renal perfusion/mental status. - [ ] Start therapeutic anticoagulation unless contraindicated. ### After confirmation - [ ] Assign AHA/ACC category A–E ± respiratory modifier. - [ ] A/B: assess outpatient safety using PESI/sPESI/Hestia and social/bleeding factors. - [ ] C–E: hospitalize. - [ ] C3/D/E: early PERT/critical-care discussion. - [ ] D/E: prepare reperfusion strategy before deterioration becomes arrest. ### Shock pathway - [ ] Avoid excessive fluids. - [ ] Vasopressor support as needed. - [ ] Activate PERT/interventional/surgical teams. - [ ] Choose systemic thrombolysis vs CDT vs MT vs surgery based on category, bleeding risk, anatomy, timing, expertise. - [ ] Consider VA-ECMO in refractory shock/arrest in an experienced system. --- ## 20. Exam-focused review ### Foundation / Step 1 Know the physiology: **PE → ↑ pulmonary vascular resistance → RV dilation/failure → septal shift → ↓ LV preload → ↓ cardiac output → obstructive shock.** Understand Virchow’s triad and why tachycardia/hypoxemia arise. ### Step 2 CK High-yield sequence: - very-low probability + PERC negative → no testing; - low/intermediate probability → D-dimer; - high probability or positive D-dimer → imaging; - confirmed PE → anticoagulate and risk-stratify; - shock → reperfusion, not anticoagulation alone. ### Step 3 / resident Know: - age-adjusted D-dimer = age × 10 µg/L FEU after age 50 in validated pathways; - apixaban 10 mg BID ×7 days → 5 mg BID; - rivaroxaban 15 mg BID ×21 days → 20 mg daily; - dabigatran/edoxaban require ≥5 days initial parenteral anticoagulation; - systemic alteplase regimen commonly 100 mg over 2 hours; - LMWH is now guideline-preferred over UFH when initial parenteral therapy is needed in most eligible patients; - hemodynamic status plus RV/biomarkers/perfusion determines treatment—not clot size alone. ### MRCP/ABIM/board level Be able to distinguish: - low-risk PE vs C3 PE vs D2 normotensive shock; - thrombolysis indications vs contraindications; - outpatient eligibility vs admission; - recurrence-risk decisions for anticoagulation duration; - CTEPD/CTEPH follow-up; - guideline-standard advanced therapy vs post-guideline emerging CDT evidence. --- ## 21. Original MCQs #### Question 1 A 34-year-old woman with pleuritic chest pain has clinician-estimated PE probability <10%. HR 82, SpO₂ 98%, no hemoptysis, no estrogen use, no prior VTE, no unilateral swelling, no recent surgery/trauma. What is the best next step? A. CTPA B. D-dimer in all cases C. Apply PERC; if all negative, no further PE testing D. Start apixaban empirically **Answer: C.** PERC can exclude PE without D-dimer in genuinely very-low-risk patients when all criteria are negative. [1] #### Question 2 A 74-year-old low/intermediate-probability patient has D-dimer 650 µg/L FEU. Using a validated age-adjusted strategy, which statement is most accurate? A. The result is automatically positive because it exceeds 500 B. The age-adjusted cutoff is approximately 740 µg/L FEU C. The age-adjusted cutoff is 74 µg/L D. Age adjustment is used only below age 50 **Answer: B.** For age >50, a commonly validated FEU cutoff is age ×10 µg/L, here approximately 740. [1,5] #### Question 3 A patient has confirmed PE, normal BP, elevated sPESI, RV dilation, positive troponin, lactate 4 mmol/L, oliguria, and cool extremities. Which concept is most important? A. Normal BP proves low-risk PE B. This can represent normotensive shock/incipient cardiopulmonary failure C. Troponin proves acute MI rather than PE D. The patient should be discharged on a DOAC **Answer: B.** End-organ hypoperfusion can precede persistent hypotension; this is the rationale for Category D2 physiology in the 2026 scheme. [1,3] #### Question 4 Which anticoagulation statement is correct in the 2026 guideline? A. UFH is always preferred to LMWH in acute PE B. LMWH is recommended over UFH when initial parenteral therapy is required in most C1–E1 patients C. Warfarin is preferred over DOACs for most eligible adults D. Anticoagulation should wait until all thrombophilia tests return **Answer: B.** LMWH is guideline-preferred over UFH for most patients requiring initial parenteral therapy, and DOACs are preferred over VKAs when eligible. [1] #### Question 5 Which apixaban regimen is evidence-based for acute VTE in a standard eligible adult? A. 2.5 mg BID from day 1 B. 5 mg daily C. 10 mg BID for 7 days, then 5 mg BID D. 10 mg daily after 5 days of heparin **Answer: C.** [4,9] #### Question 6 A normotensive patient has elevated clinical severity score but normal RV function and normal cardiac biomarkers. Which 2026 category best fits? A. A B. B C. C1 D. E1 **Answer: C.** C1 is symptomatic PE with elevated clinical severity but normal RV and biomarkers. [1,3] #### Question 7 Which statement about systemic thrombolysis is most accurate? A. It is routine for all RV-strain PE B. It should be used for all C2 patients C. It is reasonable in cardiopulmonary failure when bleeding risk is acceptable, but routine use in A–C2 is discouraged because of bleeding/ICH D. It is contraindicated in cardiac arrest from PE **Answer: C.** The benefit-risk balance changes sharply as the patient progresses toward D/E physiology. [1] #### Question 8 Which statement best reflects the 2026 catheter-directed thrombolysis evidence? A. The February guideline already incorporated PRAGUE-26 B. HI-PEITHO and PRAGUE-26 were published after the guideline evidence cutoff and suggest reduced early deterioration in selected intermediate-risk patients C. Catheter treatment is now mandatory for every C3 patient D. All catheter devices are clinically interchangeable **Answer: B.** The trials are important emerging evidence but require careful population/device-specific interpretation. [1,15,16] --- ## 22. Current guideline changes and recent research ### STANDARD OF CARE — 2026 multisociety guideline #### New A–E severity categories The 2026 guideline’s most visible conceptual change is replacement of broad low/intermediate/high-risk terminology with categories that integrate symptoms, clinical severity scores, RV function, biomarkers, respiratory compromise, transient hypotension, and end-organ perfusion. [1,3] #### PERT Multidisciplinary PERT assessment is recommended for patients at increased risk of adverse outcomes (Categories C–E) to improve care delivery. [1,3] #### Anticoagulation - LMWH over UFH when parenteral therapy is required in most eligible patients. - DOAC over VKA for most eligible patients. - Extended anticoagulation for first PE without a major reversible factor and for persistent risk factors when bleeding risk permits. [1] #### Advanced therapy - **E1:** systemic thrombolysis, CDT, MT, and surgical embolectomy are reasonable options depending on patient/center factors. - **D1–D2:** these therapies may be considered. - **A–C2:** routine systemic thrombolysis is harmful; routine advanced catheter/surgical treatment is not supported. - **C3:** evidence for routine advanced reperfusion remained uncertain in the guideline. [1,3] #### Follow-up Screen for post-PE symptoms and functional limitation for at least one year; evaluate persistent dyspnea for CTEPD/CTEPH. [1,3] --- ### EMERGING EVIDENCE — HI-PEITHO (2026) HI-PEITHO randomized **544** selected intermediate-risk PE patients with RV/LV ratio ≥1.0, elevated troponin, and at least two indicators of cardiorespiratory distress to ultrasound-facilitated catheter-directed fibrinolysis plus anticoagulation or anticoagulation alone. [15] The primary composite of PE-related death, cardiorespiratory decompensation/collapse, or symptomatic recurrent PE occurred in **4.0% vs 10.3%**. The benefit was driven mainly by less clinical deterioration; major bleeding was numerically higher but not statistically different, and no intracranial hemorrhage occurred in either group. [15] #### Interpretation This trial lowers the threshold for discussing CDT in **carefully selected higher-severity normotensive PE**, but it does not prove that every patient with RV strain should undergo an intervention. The population was highly selected, and results should not be generalized to every catheter device or lower-risk PE. [15] --- ### EMERGING EVIDENCE — PRAGUE-26 (published August 31, 2026) PRAGUE-26 randomized **558** patients with intermediate-high-risk PE to catheter-directed alteplase thrombolysis plus anticoagulation or anticoagulation alone. [16] The 7-day composite of death, recurrent PE, or cardiorespiratory decompensation/collapse occurred in: - **0.7%** with catheter-directed thrombolysis - **6.8%** with standard care - RR **0.10** (95% CI 0.02–0.44; P<0.001). [16] The difference was again driven largely by prevention of decompensation. Clinically relevant bleeding was similar (**4.6% vs 5.0%**); major bleeding was **1.4% vs 2.2%**; intracranial hemorrhage occurred in **0.7% vs 0%**. [16] #### Why this matters PRAGUE-26 was published **after** the February 2026 guideline and therefore is not incorporated into its formal recommendations. Along with HI-PEITHO, it substantially strengthens the clinical-outcome evidence for selected catheter-directed thrombolysis in intermediate-high-risk PE. #### What it does not prove - It does not establish catheter treatment as mandatory for all intermediate-risk PE. - It does not establish equivalence across all devices, lytic doses, or center expertise. - It does not eliminate intracranial or major bleeding risk. - Mortality benefit remains less certain than reduction in deterioration. A future guideline update may change the formal category-C recommendations. --- ### EXPERIMENTAL / INVESTIGATIONAL Areas still requiring stronger evidence include: - selecting the exact C2/C3 phenotype that gains net benefit from early catheter intervention; - head-to-head CDT vs mechanical thrombectomy; - optimal lytic dose and device strategy; - validated biomarkers of impending RV collapse; - long-term effects of acute catheter therapy on post-PE syndrome/CTEPH; - artificial-intelligence–assisted CT triage without compromising clinical judgment. --- ## 23. Guideline differences: 2019 ESC vs 2026 AHA/ACC The 2019 ESC guideline stratifies PE as low risk, intermediate-low, intermediate-high, or high risk using hemodynamic status, PESI/sPESI, RV dysfunction, and troponin. [8] The 2026 AHA/ACC system maps broadly as follows: [3] | 2019 ESC concept | Approximate 2026 AHA/ACC counterpart | |---|---| | Low risk | B (and some A) | | Intermediate-low | C1–C2 | | Intermediate-high | C3 | | Hemodynamic instability/high risk | D–E, with greater granularity for transient hypotension, normotensive shock, established shock, and arrest | They are not perfectly interchangeable. The 2026 model explicitly emphasizes **end-organ perfusion and respiratory modifiers**, allowing earlier recognition of impending failure. --- ## 24. References 1. Creager MA, Barnes GD, Giri J, et al. **2026 AHA/ACC/ACCP/ACEP/CHEST/SCAI/SHM/SIR/SVM/SVN Guideline for the Evaluation and Management of Acute Pulmonary Embolism in Adults.** *J Am Coll Cardiol*. 2026;87(13):1626-1710. doi: **10.1016/j.jacc.2025.11.005**. https://www.jacc.org/doi/10.1016/j.jacc.2025.11.005 2. **Correction: 2026 Acute Pulmonary Embolism Guideline.** *J Am Coll Cardiol*. 2026;88(6):713. Published August 11, 2026. doi: **10.1016/j.jacc.2026.06.033**. https://www.jacc.org/doi/10.1016/j.jacc.2026.06.033 3. Dudzinski DM, Cibotti-Sun M, Moore MM. **2026 Acute Pulmonary Embolism Guideline-at-a-Glance.** *J Am Coll Cardiol*. 2026;87(13):1620-1625. doi: **10.1016/j.jacc.2025.12.023**. 4. Kumbhani DJ, Armbruster AL, Cheng RK, et al. **Direct Oral Anticoagulants in Primary and Secondary Prevention of Thrombotic Events: 2026 ACC Scientific Statement.** *J Am Coll Cardiol*. 2026. doi: **10.1016/j.jacc.2026.05.033**. 5. Righini M, Van Es J, Den Exter PL, et al. **Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism: The ADJUST-UNLIKELY/ADJUST-PE strategy evidence.** *JAMA*. 2014;311:1117-1124. doi: **10.1001/jama.2014.2135**. 6. van der Hulle T, Cheung WY, Kooij S, et al. **Simplified diagnostic management of suspected pulmonary embolism (the YEARS study).** *Lancet*. 2017;390:289-297. doi: **10.1016/S0140-6736(17)30885-1**. 7. Meyer G, Vicaut E, Danays T, et al. **Fibrinolysis for Patients with Intermediate-Risk Pulmonary Embolism (PEITHO).** *N Engl J Med*. 2014;370:1402-1411. doi: **10.1056/NEJMoa1302097**. 8. Konstantinides SV, Meyer G, Becattini C, et al. **2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the ERS.** *Eur Heart J*. 2020;41:543-603. doi: **10.1093/eurheartj/ehz405**. 9. Agnelli G, Buller HR, Cohen A, et al. **Oral Apixaban for the Treatment of Acute Venous Thromboembolism (AMPLIFY).** *N Engl J Med*. 2013;369:799-808. doi: **10.1056/NEJMoa1302507**. 10. EINSTEIN–PE Investigators. **Oral Rivaroxaban for the Treatment of Symptomatic Pulmonary Embolism.** *N Engl J Med*. 2012;366:1287-1297. doi: **10.1056/NEJMoa1113572**. 11. Schulman S, Kearon C, Kakkar AK, et al. **Dabigatran versus Warfarin in the Treatment of Acute Venous Thromboembolism.** *N Engl J Med*. 2009;361:2342-2352. doi: **10.1056/NEJMoa0906598**. 12. Hokusai-VTE Investigators. **Edoxaban versus Warfarin for the Treatment of Symptomatic Venous Thromboembolism.** *N Engl J Med*. 2013;369:1406-1415. doi: **10.1056/NEJMoa1306638**. 13. Stevens SM, Woller SC, Kreuziger LB, et al. **Antithrombotic Therapy for VTE Disease: Second Update of the CHEST Guideline and Expert Panel Report.** *Chest*. 2021;160:e545-e608. doi: **10.1016/j.chest.2021.07.055**. 14. Kearon C, Akl EA, Ornelas J, et al. **Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report.** *Chest*. 2016;149:315-352. doi: **10.1016/j.chest.2015.11.026**. 15. Rosenfield K, Klok FA, Piazza G, et al; HI-PEITHO Investigators. **Ultrasound-Facilitated, Catheter-Directed Fibrinolysis for Acute Pulmonary Embolism.** *N Engl J Med*. 2026;394(20):1979-1990. doi: **10.1056/NEJMoa2516567**. PMID: **41910345**. 16. Clarençon F, et al. **Catheter-Directed Thrombolysis in Intermediate-High-Risk Pulmonary Embolism (PRAGUE-26).** *N Engl J Med*. Published August 31, 2026. doi: **10.1056/NEJMoa2608012**. 17. Piazza G, et al. **Extended-Duration Low-Intensity Apixaban to Prevent Recurrence in High-Risk Patients With Provoked Venous Thromboembolism (HI-PRO).** *N Engl J Med*. 2025. See ACC ESC 2025 report for trial details. 18. Castellucci LA, Chen VM, Kovacs MJ, et al. **Bleeding Risk with Apixaban vs Rivaroxaban in Acute Venous Thromboembolism (COBRRA).** *N Engl J Med*. 2026;394(11):1051-1060. doi: **10.1056/NEJMoa2510703**. 19. Piazza G, Cushman M. **AHA/ACC Acute Pulmonary Embolism Clinical Categories: Perspectives on Development and Application.** *J Am Coll Cardiol*. 2026;87(13):1554-1557. doi: **10.1016/j.jacc.2025.11.053**. --- ### Bottom line The modern approach to PE is not “diagnose clot and give anticoagulation.” It is a sequence of **probability-based diagnosis, immediate anticoagulation when appropriate, and rapid physiologic risk stratification of the right ventricle and systemic perfusion**. The 2026 AHA/ACC categories make a critical distinction between compensated RV strain and **incipient cardiopulmonary failure**, where early escalation may prevent arrest. Anticoagulation remains the foundation of treatment; advanced reperfusion is standard in shock-level disease and increasingly evidence-supported in carefully selected higher-risk normotensive patients, but treatment must remain individualized to bleeding risk, physiology, anatomy, and local expertise.19:Tc5fd,## One-minute summary **Acute pulmonary embolism (PE)** is obstruction of the pulmonary arterial circulation by thrombus, usually arising from deep veins of the legs or pelvis. The immediate threat is **acute right-ventricular (RV) pressure overload**, which may progress from compensated RV strain to reduced left-ventricular preload, systemic hypotension, obstructive shock, and cardiac arrest. The 2026 multisociety AHA/ACC guideline introduces a new **A–E Acute PE Clinical Category system** that moves beyond the older low/intermediate/high-risk labels. [1,3] - **A:** incidental/asymptomatic PE. - **B:** symptomatic PE with a low clinical severity score. - **C:** symptomatic PE with an elevated clinical severity score, stratified by RV dysfunction and cardiac biomarkers. - **D:** incipient cardiopulmonary failure, such as transient hypotension or normotensive shock/end-organ hypoperfusion. - **E:** established cardiopulmonary failure, including persistent hypotension with shock or cardiac arrest. [1,3] The core clinical pathway is: **Estimate pretest probability → use PERC only in truly very-low-risk patients → use D-dimer when appropriate → CTPA (or V/Q when needed) → confirm PE → immediately risk-stratify → anticoagulate unless contraindicated → identify who is safe for outpatient care vs who needs monitored hospitalization or advanced reperfusion.** High-yield 2026 practice points: [1] - A negative **age-adjusted D-dimer** can avoid imaging in appropriate low/intermediate-probability patients over age 50. - **CTPA** is the usual first-line definitive test; V/Q scanning is valuable when iodinated contrast is unsuitable. - **LMWH is preferred over UFH** when initial parenteral anticoagulation is required in most C1–E1 patients. - **DOACs are preferred over vitamin K antagonists** for most eligible adults. - Advanced reperfusion therapies are **reasonable in Category E1** and may be considered in **D1–D2**; routine systemic thrombolysis is harmful in A–C2. - **PERT assessment is recommended** for higher-risk categories to improve care delivery. - Follow-up should include anticoagulation review and screening for persistent dyspnea/functional limitation and chronic thromboembolic pulmonary disease (CTEPD). Two major randomized trials published after the guideline evidence cutoff—**HI-PEITHO** and **PRAGUE-26**—showed fewer early clinical deterioration events with catheter-directed thrombolysis in selected intermediate-risk/intermediate-high-risk patients. These are important **emerging evidence**, but they do not yet justify indiscriminate catheter treatment of all normotensive PE. [15,16] --- ## 1. Definition and core concepts ### 1.1 Definition Acute PE is partial or complete obstruction of one or more pulmonary arteries by embolic material, overwhelmingly thrombus. Most thrombi originate from lower-extremity or pelvic deep venous thrombosis (DVT), although upper-extremity catheter-associated thrombosis and other sources occur. #### Anatomical terms - **Subsegmental PE:** clot limited to subsegmental pulmonary arteries. - **Segmental PE:** segmental branch involvement. - **Lobar/proximal PE:** lobar or main pulmonary artery involvement. - **Saddle PE:** thrombus straddling the pulmonary artery bifurcation. This is an anatomical description, **not a severity category**; a saddle embolus can be hemodynamically stable, while a smaller clot burden can be fatal in a patient with limited cardiopulmonary reserve. ### 1.2 The main physiological problem is RV afterload Abrupt obstruction plus vasoconstriction increases pulmonary vascular resistance. The RV, a thin-walled chamber adapted to a low-pressure system, dilates under acute pressure load. RV wall tension and oxygen demand rise while coronary perfusion can fall. The interventricular septum shifts toward the LV, impairing LV filling. Cardiac output declines; systemic hypotension further reduces RV coronary perfusion, creating a vicious cycle. #### Hemodynamic spiral ```text Pulmonary arterial obstruction ↓ ↑ Pulmonary vascular resistance ↓ RV dilation + ↑ wall stress ↓ Tricuspid regurgitation + septal shift ↓ ↓ LV preload and cardiac output ↓ Hypotension / systemic hypoperfusion ↓ ↓ RV coronary perfusion ↓ RV ischemia → worsening RV failure ↓ Obstructive shock / cardiac arrest ``` This explains why **blood pressure alone is insufficient** for risk assessment: a patient may be normotensive while already developing low cardiac output, lactate elevation, [acute kidney injury](/library/acute-kidney-injury), oliguria, or altered mental status. --- ## 2. Epidemiology and risk factors PE is a major manifestation of venous thromboembolism (VTE). Risk follows **Virchow’s triad**: venous stasis, endothelial injury, and hypercoagulability. ### 2.1 Major provoking factors #### Strong transient factors - Major surgery, especially orthopedic/pelvic surgery - Major trauma or fracture - Prolonged hospitalization or severe acute illness - Marked immobilization - Pregnancy and postpartum state #### Persistent factors - Active cancer - Chronic inflammatory or autoimmune disease - Persistent immobility - Antiphospholipid syndrome (APS) - Selected inherited thrombophilias #### Common acquired risk factors - Prior VTE - Increasing age - Obesity - Estrogen-containing hormonal therapy - Heart failure - Chronic lung disease - Nephrotic syndrome - Central venous catheters - Myeloproliferative neoplasms ### 2.2 Provoked vs unprovoked is clinically useful—but imperfect The traditional binary distinction helps estimate recurrence risk, but risk is a continuum. A PE after major surgery is very different from a PE after a minor transient trigger in a patient with obesity, inflammatory disease, and previous VTE. Modern duration decisions increasingly incorporate **persistent risk, recurrence risk, bleeding risk, and patient preference**, rather than relying on a single label. [1,17] --- ## 3. Clinical presentation PE ranges from asymptomatic incidental imaging findings to sudden cardiac arrest. ### 3.1 Common symptoms - Acute or progressive dyspnea - Pleuritic chest pain - Nonpleuritic chest pressure - Cough - Hemoptysis - Syncope or presyncope - Palpitations - Unilateral leg pain/swelling ### 3.2 Common signs - Tachycardia - Tachypnea - Hypoxemia - Fever (usually low grade if present) - Unilateral leg swelling/tenderness - Elevated JVP - RV heave - Loud P2 - New tricuspid regurgitation murmur - Hypotension, cool extremities, altered mental status, oliguria in advanced disease ### 3.3 Red flags for impending deterioration - Syncope with persistent tachycardia or borderline BP - SBP near 90–110 mm Hg or a meaningful fall from baseline - Rising lactate - Increasing oxygen requirement - RR ≥30/min - New confusion - Oliguria/acute kidney injury - Marked RV dilation or reduced RV function - Elevated troponin with RV dysfunction - Free-floating right-heart clot-in-transit A normotensive patient with several of these features may be in **incipient cardiopulmonary failure**, not “stable PE.” [1] --- ## 4. Differential diagnosis | Condition | Features that overlap | Clues favoring alternative diagnosis | |---|---|---| | [Acute coronary syndrome](/library/acute-coronary-syndrome) | Chest pain, dyspnea, troponin elevation | Ischemic ECG pattern/coronary syndrome; remember PE can also elevate troponin | | Pneumonia | Dyspnea, pleuritic pain, fever, hypoxemia | Focal infiltrate, infectious prodrome; PE and pneumonia can coexist | | Pneumothorax | Sudden dyspnea/pleuritic pain | Unilateral absent breath sounds, pleural line on ultrasound, CXR findings | | Acute aortic syndrome | Chest/back pain, syncope | Pulse/BP differential, aortic imaging findings | | Acute heart failure | Dyspnea, hypoxemia, elevated BNP | Pulmonary edema, LV dysfunction; PE can precipitate RV-predominant failure | | Pericarditis | Pleuritic pain | Positional pain, diffuse ST elevation/PR depression | | COPD/asthma exacerbation | Dyspnea, tachycardia | Wheeze/known disease; PE remains possible if unexplained deterioration | | Panic/hyperventilation | Dyspnea, chest discomfort | Diagnosis of exclusion when PE probability is nontrivial | | Sepsis | Tachycardia, hypotension, lactate elevation | Infection source; PE can coexist with systemic illness | --- ## 5. Diagnostic strategy: probability before testing The biggest diagnostic error is ordering tests without first considering **pretest probability**. D-dimer is useful when disease probability is low enough that a negative result safely rules out PE; it is inefficient in high-probability patients and frequently positive in hospitalized, elderly, pregnant, inflammatory, postoperative, and cancer populations. ### 5.1 Step 1 — Is the patient unstable? If the patient has shock or cardiac arrest and PE is strongly suspected: - Resuscitate immediately. - Obtain bedside echocardiography/POCUS if it can be performed without delaying treatment. - Obtain CTPA if the patient can safely reach CT. - Activate PERT/critical care/interventional/surgical resources early. Echocardiography is **not recommended to confirm or exclude PE in a stable suspected case**, because RV findings are not sufficiently specific; its major value is risk stratification and bedside assessment in unstable patients. [1] ### 5.2 Step 2 — Estimate clinical probability Validated tools include: - Wells score - Revised Geneva score - Clinical gestalt in experienced hands The practical purpose is to classify the patient into a pathway where PE is: - very unlikely, - low/intermediate probability, or - high probability. ### 5.3 PERC — only for very-low-risk patients The **Pulmonary Embolism Rule-out Criteria (PERC)** may allow no further testing when clinician-estimated pretest probability is very low (commonly <15%) and **all 8 criteria are absent**: 1. Age ≥50 years 2. Pulse ≥100/min 3. SpO₂ <95% 4. Unilateral leg swelling 5. Hemoptysis 6. Estrogen use 7. Prior DVT/PE 8. Recent surgery or trauma requiring hospitalization If any PERC criterion is positive, PERC does not rule out PE—move to a D-dimer or imaging strategy depending on pretest probability. [1] **Pitfall:** PERC is not a “PE score” to apply indiscriminately to every patient with chest pain. ### 5.4 D-dimer #### Standard threshold A highly sensitive D-dimer below the assay cutoff (often 500 µg/L FEU) excludes PE in appropriately selected low/intermediate-probability patients. #### Age-adjusted D-dimer For patients older than 50 years, a commonly validated threshold is: **Age × 10 µg/L FEU** Example: age 72 → negative threshold <720 µg/L FEU, assuming the assay uses compatible FEU units. [1,5] Always confirm laboratory units and assay convention; D-dimer units are not interchangeable. ### 5.5 YEARS strategy The YEARS algorithm assesses three items: - Clinical signs of DVT - Hemoptysis - PE judged the most likely diagnosis Typical thresholds: [6] - **No YEARS items:** D-dimer <1000 µg/L FEU can exclude PE. - **≥1 YEARS item:** D-dimer <500 µg/L FEU can exclude PE. A pregnancy-adapted YEARS pathway is an evidence-based option in selected pregnant patients and can reduce unnecessary chest imaging when applied correctly. [1] --- ## 6. Imaging and bedside tests ### 6.1 CTPA **CT pulmonary angiography (CTPA)** is the standard definitive imaging test in most adults. It provides: - direct visualization of emboli; - clot location/burden; - alternative diagnoses; - RV/LV ratio for risk stratification; - signs of chronic thromboembolic disease. The 2026 guideline recommends **numerical RV/LV ratio reporting** rather than subjective RV enlargement when CTPA is performed. [1] ### 6.2 Ventilation-perfusion (V/Q) scanning V/Q scanning is especially useful when: - iodinated contrast is contraindicated; - severe contrast allergy exists; - renal function makes CTPA undesirable in the individual context; - radiation distribution is a concern, including selected pregnancy pathways; - chest radiograph is relatively normal, improving interpretability. ### 6.3 Compression ultrasonography Finding a proximal DVT can establish VTE and may support treatment when chest imaging is impossible or undesirable, but a negative leg ultrasound does **not** exclude PE. ### 6.4 Echocardiography In confirmed PE, echo assists risk assessment by evaluating RV size/function and pulmonary pressures. The August 11, 2026 correction to the AHA/ACC guideline clarified right-heart echocardiographic parameters. [2] | Parameter | Abnormal / concerning threshold or finding | |---|---| | RV/LV end-diastolic ratio | >0.9 abnormal in the guideline framework | | RV end-diastolic dimension | ≥30 mm in an RV-focused parasternal long-axis view, or basal RV EDD ≥41 mm in an apical RV-focused view | | TAPSE | ≤1.7 cm abnormal | | TDI S′ velocity | ≤9.5 cm/s abnormal | | TR velocity | ≥2.9 m/s suggests pulmonary hypertension | | Other findings | McConnell sign, paradoxical septal motion, reduced IVC respirophasic collapse, elevated estimated RV systolic pressure | No single echo sign proves PE; interpret the overall pattern and clinical context. ### 6.5 ECG Possible findings: - Sinus tachycardia (most common) - Right bundle-branch block - Right-axis deviation - Anterior T-wave inversion - S1Q3T3 pattern - Atrial arrhythmias **S1Q3T3 is neither sensitive nor specific** and should never be used to rule in or rule out PE. ### 6.6 Laboratory biomarkers #### Troponin Elevation reflects RV myocardial injury and is prognostic in confirmed PE; it is not specific for PE. #### BNP/NT-proBNP Reflects RV wall stress and helps risk stratification. #### Lactate Elevated lactate can reveal low-output physiology/end-organ hypoperfusion despite preserved blood pressure. In the 2026 framework it is important for identifying **normotensive shock / Category D2 physiology**. [1,3] --- ## 7. 2026 AHA/ACC Acute PE Clinical Categories The new classification is designed to connect bedside severity directly to disposition and therapy. [1,3] | Category | Clinical picture | Key objective features | Typical disposition/implication | |---|---|---|---| | **A** | Subclinical/incidental, asymptomatic PE | No PE symptoms | Usually outpatient if no separate reason for admission | | **B** | Symptomatic, low clinical severity | Low PESI/sPESI/Hestia profile | Early discharge/outpatient treatment often appropriate | | **C1** | Symptomatic, elevated clinical severity | Normal RV and normal cardiac biomarkers | Hospitalization; anticoagulation | | **C2** | Symptomatic, elevated severity | RV abnormality **or** ≥1 abnormal cardiac biomarker | Hospitalization; closer monitoring | | **C3** | Symptomatic, elevated severity | RV abnormality **and** ≥1 abnormal cardiac biomarker | Higher deterioration risk; monitored care/PERT consideration | | **D1** | Incipient cardiopulmonary failure | Transient/recurrent hypotension or relative hypotension without established end-organ hypoperfusion | High-acuity monitored care; advanced therapy may be considered | | **D2** | Incipient failure with hypoperfusion | Transient/relative hypotension plus end-organ hypoperfusion such as lactate >2 mmol/L, AKI, oliguria, mental-status change, low cardiac index/MAP | Critical-care level; PERT; advanced reperfusion consideration | | **E1** | Cardiopulmonary failure | Persistent/recurrent hypotension with cardiogenic shock | Advanced therapy is generally reasonable if feasible | | **E2** | Refractory failure / arrest | Refractory shock or cardiac arrest | Resuscitation, systemic lysis when appropriate, ECMO/advanced rescue in expert centers | #### Respiratory modifier “R” The 2026 system adds an **R modifier** when significant respiratory compromise is present. In Category C this includes features such as SpO₂ <90%, RR ≥30/min, or supplemental oxygen requirement; more advanced categories use higher oxygen/ventilatory support thresholds. [1,3] #### Why this is better than “massive/submassive” The older terminology can hide important gradients. A normotensive patient with RV dysfunction, positive troponin, lactate 4 mmol/L, oliguria, and escalating oxygen needs is much sicker than another normotensive patient with mild RV dilation alone. The A–E framework explicitly identifies that difference. --- ## 8. PESI, sPESI, and Hestia ### 8.1 PESI/sPESI These scores estimate short-term mortality and are most helpful when considering outpatient management. A **sPESI of 0** identifies a low-risk group when other outpatient criteria are satisfied. ### 8.2 Hestia criteria Hestia is a pragmatic exclusion checklist for outpatient treatment, incorporating hemodynamic instability, oxygen requirement, bleeding risk, severe pain needing IV medication, renal/liver failure, pregnancy, social barriers, and other practical concerns. **Important:** A low PESI/sPESI does not override clinical judgment, RV dysfunction, active bleeding, inability to obtain medication, severe comorbidity, or inadequate follow-up. --- ## 9. Acute management algorithm ```text Suspected PE ↓ Is patient in shock / peri-arrest? ├─ Yes → ABC resuscitation + bedside echo if useful + urgent CTPA if feasible │ → therapeutic anticoagulation if not contraindicated │ → PERT / ICU / interventional / surgical activation │ → consider immediate reperfusion strategy └─ No ↓ Estimate pretest probability ↓ Very low risk + all PERC negative? ├─ Yes → PE ruled out without D-dimer └─ No ↓ Low/intermediate probability → D-dimer strategy ├─ Negative → PE excluded └─ Positive → CTPA (or V/Q) High probability → proceed directly to imaging ↓ PE confirmed ↓ Anticoagulate unless contraindicated ↓ Risk stratify: PESI/sPESI/Hestia + RV + troponin/BNP + lactate + BP/perfusion + oxygen ↓ A/B → outpatient/early discharge when safe C → hospitalize; monitor intensity by C1/C2/C3 + R D → critical/step-down care + PERT; consider advanced reperfusion E → shock/arrest pathway; advanced reperfusion ± VA-ECMO in expert center ``` --- ## 10. Anticoagulation — STANDARD OF CARE Unless there is an absolute contraindication, **therapeutic anticoagulation should be initiated for acute PE** to reduce recurrence and death. [1] ### 10.1 Initial parenteral anticoagulation When parenteral therapy is required, the 2026 guideline recommends **LMWH over UFH** for most patients in Categories C1–E1 because LMWH reduces recurrent VTE and major bleeding. [1] #### When UFH can still be advantageous UFH is often selected when: - an immediate invasive procedure or thrombolysis is likely and rapid titration/reversal is desired; - severe renal dysfunction limits LMWH use; - extremely unstable physiology requires a highly controllable infusion; - local advanced-therapy protocols specify UFH. Do not treat “UFH for every high-risk PE” as a universal rule; the 2026 guideline explicitly prefers LMWH when parenteral therapy is required in most eligible patients. [1] ### 10.2 DOACs For eligible adults, **DOACs are recommended over vitamin K antagonists**. [1] Common evidence-based VTE regimens: [4] | Drug | Initial phase | Primary treatment | |---|---|---| | **Apixaban** | 10 mg PO twice daily for 7 days | 5 mg PO twice daily | | **Rivaroxaban** | 15 mg PO twice daily with food for 21 days | 20 mg PO once daily with food | | **Dabigatran** | Requires ≥5 days of parenteral anticoagulation first | 150 mg PO twice daily | | **Edoxaban** | Requires ≥5 days of parenteral anticoagulation first | 60 mg PO once daily in standard eligible patients | **Safety note:** renal function, hepatic function, age, weight, drug interactions, bleeding risk, and product-specific labeling must be checked before prescribing. Edoxaban and other agents have label-defined dose modifications that should not be guessed from memory. #### 2026 comparative evidence The COBRRA randomized trial compared apixaban with rivaroxaban for acute VTE and found clinically relevant bleeding at 3 months in **3.3% vs 7.1%**, respectively, with similar VTE efficacy. The 2026 ACC scientific statement therefore suggests apixaban may be preferred for many patients when either agent is otherwise suitable. This is an evolving comparative-practice consideration rather than a declaration that rivaroxaban is inappropriate. [4,18] ### 10.3 Empiric anticoagulation before imaging If PE is strongly suspected, imaging is delayed, and bleeding risk is low, the 2026 guideline states that therapeutic anticoagulation may be beneficial in patients with a clinical picture equivalent to **Category C2 or higher**. [1] This is not an excuse to anticoagulate every low-probability patient before diagnosis. --- ## 11. Reperfusion and advanced therapies The central decision is whether anticoagulation alone is sufficient or whether clot removal/lysis is needed because the RV is failing or likely to fail. ### 11.1 Systemic thrombolysis #### Standard regimen The most commonly used FDA-approved alteplase regimen for PE is: **Alteplase 100 mg IV over 2 hours.** [1] Lower-dose systemic regimens may be considered in selected circumstances to reduce bleeding, but evidence is less robust and protocols vary. [1] #### Who should receive systemic thrombolysis? | 2026 category | Systemic lysis position | |---|---| | A–C1 | **Harm / do not use routinely** | | C2 | **Harm / do not use routinely** | | C3 | Benefit uncertain; highly individualized if advanced therapy is contemplated | | D1–D2 | May be considered with acceptable bleeding risk | | E1–E2 | Reasonable when advanced reperfusion is indicated and bleeding risk is acceptable | This explains a classic board principle: **routine fibrinolysis for a normotensive intermediate-risk PE is not standard care**. The PEITHO trial reduced hemodynamic decompensation but increased major extracranial bleeding and hemorrhagic stroke with systemic tenecteplase, without a mortality advantage sufficient to justify routine use. [7] ### 11.2 Catheter-directed thrombolysis (CDT) The 2026 guideline position, based largely on pre-2025 evidence, is: [1,3] - **E1:** CDT + anticoagulation is reasonable. - **D1–D2:** may be considered when advanced therapy is being considered. - **C2–C3:** benefit vs anticoagulation alone was considered uncertain. - **A–C1:** routine catheter intervention has no benefit. This field changed materially after the evidence cutoff; see HI-PEITHO and PRAGUE-26 below. ### 11.3 Mechanical thrombectomy For catheter-based mechanical thrombectomy (MT): [1] - **E1:** reasonable compared with anticoagulation alone. - **D1–D2:** may be considered. - **C2–C3:** benefit remains uncertain for routine use. - A–C1: not routinely beneficial. A major attraction is avoiding or minimizing thrombolytic exposure, but access-site bleeding, pulmonary-artery injury, blood loss, procedural deterioration, and device-specific complications remain possible. ### 11.4 Surgical embolectomy Surgical embolectomy is reasonable in **E1** and may be considered in selected **D1–D2** patients, especially when thrombolysis is contraindicated or has failed and surgical expertise is immediately available. [1] It can also be attractive for: - central clot burden with shock; - right-heart clot-in-transit; - selected patients with a patent foramen ovale and systemic embolic risk; - situations where catheter options are unsuitable. ### 11.5 Right-heart clot-in-transit A free-floating right-atrial/RV thrombus is uncommon but high risk. In Categories C3–E2, the 2026 guideline considers advanced therapy reasonable over anticoagulation alone to reduce deterioration, although randomized comparative evidence is limited. [1] ### 11.6 VA-ECMO **Venoarterial extracorporeal membrane oxygenation (VA-ECMO)** can provide circulatory/oxygenation support in refractory cardiogenic shock or arrest from PE in expert centers. It is usually a bridge to recovery or definitive reperfusion, not treatment of the clot itself. [1] --- ## 12. Hemodynamic and respiratory support ### 12.1 Oxygen and ventilation Correct hypoxemia while avoiding interventions that precipitate RV collapse. Positive-pressure ventilation can reduce venous return and increase RV afterload. In a tenuous PE patient, deep sedation and intubation may trigger sudden cardiovascular collapse. If intubation is unavoidable: - involve experienced airway/critical-care staff; - optimize preload and vasopressor support before induction; - use hemodynamically cautious induction; - minimize excessive PEEP/airway pressures while maintaining adequate oxygenation. ### 12.2 Fluids The failing RV is preload-sensitive but easily overdistended. Large indiscriminate fluid boluses can worsen septal shift and cardiac output. Use **small, reassessed fluid challenges** only when true preload deficiency is plausible. Stop if JVP/RV dilation worsens without improved perfusion. ### 12.3 Vasopressors/inotropes In obstructive shock, vasopressor support is often required to restore systemic pressure and RV coronary perfusion while definitive reperfusion is arranged. Norepinephrine is commonly favored in shock physiology; inotropes may be added for severe low-output RV failure under critical-care guidance. The goal is not simply a numeric blood pressure—it is restoration of **organ perfusion** without excessive tachycardia or RV oxygen demand. --- ## 13. Disposition ### Category A The 2026 guideline states that asymptomatic Category A patients can generally be discharged rather than hospitalized, assuming no competing reason for admission and a safe treatment/follow-up plan. [1,3] ### Category B Early discharge/outpatient treatment is generally recommended if: - low PESI/sPESI/Hestia risk; - no oxygen/hemodynamic instability; - no major bleeding risk; - reliable access to anticoagulation; - adequate home support and follow-up. ### Categories C–E Hospitalization is recommended because of increasing deterioration risk. Level of care escalates with: - C3 physiology; - respiratory modifier; - lactate/end-organ hypoperfusion; - transient hypotension; - escalating oxygen; - shock/arrest. --- ## 14. Duration of anticoagulation The 2026 guideline defines: - **Initial treatment phase:** first **3–6 months**. - **Extended phase:** beyond 6 months. [1] ### 14.1 Major reversible provoking factor If a first PE occurred because of a **major reversible risk factor** and that factor has resolved, stopping anticoagulation after the initial treatment phase is generally recommended when recurrence risk is low and there is no other indication for continued therapy. [1] ### 14.2 No major reversible factor / unprovoked PE Extended anticoagulation is recommended for many patients after a first PE without a major reversible risk factor, assuming bleeding risk is acceptable. [1] ### 14.3 Persistent risk factor Continued anticoagulation is generally recommended while a clinically important persistent risk factor remains, with periodic reassessment. ### 14.4 Extended-dose options Evidence-supported extended regimens include: [4] - **Apixaban 2.5 mg twice daily** after completion of primary therapy in selected patients. - **Rivaroxaban 10 mg once daily** in selected patients. - Full-dose regimens remain appropriate in patients with higher recurrence risk. Duration is a shared decision balancing recurrence risk, bleeding risk, comorbidity, preference, cost, adherence, and changing life circumstances. --- ## 15. Special populations ### 15.1 Pregnancy Pregnancy changes both diagnostic and treatment decisions. - Pregnancy-adapted YEARS can reduce imaging in appropriate patients. - **LMWH is generally preferred** for treatment during pregnancy. - UFH may be useful close to delivery or when rapid reversibility is needed. - DOACs should not be used routinely in pregnancy and are generally avoided during breastfeeding because of insufficient safety data. - Warfarin is teratogenic and is generally avoided during pregnancy, although there are narrow specialist-managed exceptions in mechanical-valve care unrelated to routine PE treatment. A pregnant patient with shock from PE requires immediate multidisciplinary maternal resuscitation; maternal survival is the priority. ### 15.2 Cancer-associated PE DOACs or LMWH are effective. Choice depends on: - bleeding risk, particularly GI/GU mucosal tumors; - thrombocytopenia; - drug interactions; - vomiting/malabsorption; - renal function; - planned procedures; - patient preference. The 2026 ACC statement notes a strong evidence base for apixaban in cancer-associated thrombosis, while LMWH remains valuable in high-bleeding-risk or interaction-heavy situations. [4] ### 15.3 Antiphospholipid syndrome For thrombotic APS—especially high-risk/triple-positive APS—**vitamin K antagonist therapy is generally preferred over DOACs** because DOACs have been associated with excess recurrent arterial/thrombotic events in high-risk APS. ### 15.4 Severe renal disease Renal clearance differs substantially among DOACs. Severe CKD/dialysis requires drug-specific labeling and specialist judgment; do not apply standard VTE doses automatically. UFH or carefully selected anticoagulant strategies may be preferable in some patients. ### 15.5 Liver disease Hepatic dysfunction affects both coagulation and DOAC metabolism. The 2026 ACC statement supports individualized use by Child-Pugh class and notes that evidence becomes very limited in severe hepatic disease. [4] ### 15.6 Isolated subsegmental PE Management is individualized. Important questions include: - Is the diagnosis radiographically certain? - Is there proximal DVT? - Is the patient pregnant, has active cancer, prior VTE, impaired cardiopulmonary reserve, or persistent provoking risk? - Is the patient symptomatic? - Can reliable surveillance be performed? Selected low-risk patients with isolated subsegmental PE and no DVT may be candidates for surveillance in some guidelines, but many patients have enough recurrence risk to favor anticoagulation. This requires careful shared decision-making rather than an automatic rule. [17] --- ## 16. Complications | Complication | Clinical clues | Management principle | |---|---|---| | Obstructive shock | Hypotension, cool skin, oliguria, lactate rise, confusion | Vasopressor support + urgent reperfusion strategy | | Cardiac arrest | Often PEA | CPR + high suspicion; systemic lysis/ECMO/advanced reperfusion as appropriate | | Recurrent PE | New dyspnea/chest pain/syncope while treated | Verify adherence/dose/interactions; repeat imaging; consider alternate anticoagulant class | | Major bleeding | GI, intracranial, retroperitoneal, access-site | Stop/reverse anticoagulation as appropriate; hemostasis; reassess thrombosis risk | | Chronic thromboembolic pulmonary disease | Persistent dyspnea/exercise intolerance ≥3 months | Structured evaluation; V/Q often central to CTEPD workup; refer expert center | | CTEPH | Persistent pulmonary hypertension from chronic organized thrombi | Expert-center evaluation for endarterectomy/BPA/medical therapy | | Post-PE syndrome | Dyspnea, reduced exercise capacity despite no CTEPH | Exclude CTEPD, cardiac/pulmonary disease; rehabilitation and targeted management | --- ## 17. Follow-up after acute PE The acute event is not over at discharge. The 2026 guideline recommends: [1,3] - early post-discharge contact/assessment can be helpful, often within the first week; - a clinical visit **by about 3 months** to assess symptoms, bleeding, adherence, provoking factors, and anticoagulation duration; - asking about **dyspnea and functional limitation for at least 1 year** after PE; - evaluating persistent symptoms after ≥3 months of anticoagulation for CTEPD/CTEPH or other causes. #### Follow-up checklist - Confirm anticoagulant and correct dose. - Check renal/hepatic function when relevant. - Review bleeding and interacting medications. - Clarify whether the PE was major-provoked, minor-provoked, persistent-risk, or unprovoked. - Decide initial vs extended anticoagulation plan. - Encourage safe early ambulation. - Review cancer screening based on age/standard indications rather than indiscriminate extensive testing. - Ask about exertional dyspnea, exercise intolerance, chest pain, syncope, edema. --- ## 18. Common pitfalls | Pitfall | Why it is dangerous | Better approach | |---|---|---| | Ordering D-dimer in a high-probability patient | Delays definitive imaging and is likely positive | Proceed directly to imaging | | Using PERC in moderate-risk patients | PERC was designed for very-low pretest probability | Estimate probability first | | Treating saddle location as synonymous with “massive PE” | Anatomy ≠ physiology | Risk-stratify by BP, perfusion, RV function, biomarkers, respiratory status | | Calling a normotensive patient “stable” despite lactate/AKI | Misses normotensive shock | Assess end-organ perfusion and Category D physiology | | Giving liters of crystalloid for RV shock | Can overdistend RV and reduce LV filling | Small, reassessed bolus only if preload-responsive; vasopressors/reperfusion early | | Intubating a tenuous PE patient without hemodynamic preparation | Induction/positive pressure can precipitate arrest | Optimize pressors/preload; expert airway strategy | | Routine systemic lysis in intermediate-risk PE | Major bleeding/ICH risk | Anticoagulation + monitoring; select advanced therapy by deterioration risk | | Assuming all catheter devices have equal RCT evidence | Devices/mechanisms differ | Apply trial data only to comparable technology/populations | | Stopping anticoagulation automatically at 3 months | Recurrence risk may remain high | Reassess provoking/persistent factors and bleeding risk | | Ignoring persistent dyspnea after PE | Misses CTEPD/CTEPH | Structured follow-up for at least a year | --- ## 19. Acute management checklist ### First 10–30 minutes - [ ] ABC assessment; identify shock/arrest. - [ ] Oxygen as needed; avoid unplanned deep sedation/intubation in RV failure. - [ ] IV access, ECG, continuous monitoring. - [ ] Determine pretest probability if diagnosis is not established. - [ ] PERC only if truly very low risk. - [ ] D-dimer if low/intermediate probability and appropriate. - [ ] CTPA or V/Q when indicated. - [ ] If confirmed: assess BP trend, oxygen requirement, RV, troponin/BNP, lactate, renal perfusion/mental status. - [ ] Start therapeutic anticoagulation unless contraindicated. ### After confirmation - [ ] Assign AHA/ACC category A–E ± respiratory modifier. - [ ] A/B: assess outpatient safety using PESI/sPESI/Hestia and social/bleeding factors. - [ ] C–E: hospitalize. - [ ] C3/D/E: early PERT/critical-care discussion. - [ ] D/E: prepare reperfusion strategy before deterioration becomes arrest. ### Shock pathway - [ ] Avoid excessive fluids. - [ ] Vasopressor support as needed. - [ ] Activate PERT/interventional/surgical teams. - [ ] Choose systemic thrombolysis vs CDT vs MT vs surgery based on category, bleeding risk, anatomy, timing, expertise. - [ ] Consider VA-ECMO in refractory shock/arrest in an experienced system. --- ## 20. Exam-focused review ### Foundation / Step 1 Know the physiology: **PE → ↑ pulmonary vascular resistance → RV dilation/failure → septal shift → ↓ LV preload → ↓ cardiac output → obstructive shock.** Understand Virchow’s triad and why tachycardia/hypoxemia arise. ### Step 2 CK High-yield sequence: - very-low probability + PERC negative → no testing; - low/intermediate probability → D-dimer; - high probability or positive D-dimer → imaging; - confirmed PE → anticoagulate and risk-stratify; - shock → reperfusion, not anticoagulation alone. ### Step 3 / resident Know: - age-adjusted D-dimer = age × 10 µg/L FEU after age 50 in validated pathways; - apixaban 10 mg BID ×7 days → 5 mg BID; - rivaroxaban 15 mg BID ×21 days → 20 mg daily; - dabigatran/edoxaban require ≥5 days initial parenteral anticoagulation; - systemic alteplase regimen commonly 100 mg over 2 hours; - LMWH is now guideline-preferred over UFH when initial parenteral therapy is needed in most eligible patients; - hemodynamic status plus RV/biomarkers/perfusion determines treatment—not clot size alone. ### MRCP/ABIM/board level Be able to distinguish: - low-risk PE vs C3 PE vs D2 normotensive shock; - thrombolysis indications vs contraindications; - outpatient eligibility vs admission; - recurrence-risk decisions for anticoagulation duration; - CTEPD/CTEPH follow-up; - guideline-standard advanced therapy vs post-guideline emerging CDT evidence. --- ## 21. Original MCQs #### Question 1 A 34-year-old woman with pleuritic chest pain has clinician-estimated PE probability <10%. HR 82, SpO₂ 98%, no hemoptysis, no estrogen use, no prior VTE, no unilateral swelling, no recent surgery/trauma. What is the best next step? A. CTPA B. D-dimer in all cases C. Apply PERC; if all negative, no further PE testing D. Start apixaban empirically **Answer: C.** PERC can exclude PE without D-dimer in genuinely very-low-risk patients when all criteria are negative. [1] #### Question 2 A 74-year-old low/intermediate-probability patient has D-dimer 650 µg/L FEU. Using a validated age-adjusted strategy, which statement is most accurate? A. The result is automatically positive because it exceeds 500 B. The age-adjusted cutoff is approximately 740 µg/L FEU C. The age-adjusted cutoff is 74 µg/L D. Age adjustment is used only below age 50 **Answer: B.** For age >50, a commonly validated FEU cutoff is age ×10 µg/L, here approximately 740. [1,5] #### Question 3 A patient has confirmed PE, normal BP, elevated sPESI, RV dilation, positive troponin, lactate 4 mmol/L, oliguria, and cool extremities. Which concept is most important? A. Normal BP proves low-risk PE B. This can represent normotensive shock/incipient cardiopulmonary failure C. Troponin proves acute MI rather than PE D. The patient should be discharged on a DOAC **Answer: B.** End-organ hypoperfusion can precede persistent hypotension; this is the rationale for Category D2 physiology in the 2026 scheme. [1,3] #### Question 4 Which anticoagulation statement is correct in the 2026 guideline? A. UFH is always preferred to LMWH in acute PE B. LMWH is recommended over UFH when initial parenteral therapy is required in most C1–E1 patients C. Warfarin is preferred over DOACs for most eligible adults D. Anticoagulation should wait until all thrombophilia tests return **Answer: B.** LMWH is guideline-preferred over UFH for most patients requiring initial parenteral therapy, and DOACs are preferred over VKAs when eligible. [1] #### Question 5 Which apixaban regimen is evidence-based for acute VTE in a standard eligible adult? A. 2.5 mg BID from day 1 B. 5 mg daily C. 10 mg BID for 7 days, then 5 mg BID D. 10 mg daily after 5 days of heparin **Answer: C.** [4,9] #### Question 6 A normotensive patient has elevated clinical severity score but normal RV function and normal cardiac biomarkers. Which 2026 category best fits? A. A B. B C. C1 D. E1 **Answer: C.** C1 is symptomatic PE with elevated clinical severity but normal RV and biomarkers. [1,3] #### Question 7 Which statement about systemic thrombolysis is most accurate? A. It is routine for all RV-strain PE B. It should be used for all C2 patients C. It is reasonable in cardiopulmonary failure when bleeding risk is acceptable, but routine use in A–C2 is discouraged because of bleeding/ICH D. It is contraindicated in cardiac arrest from PE **Answer: C.** The benefit-risk balance changes sharply as the patient progresses toward D/E physiology. [1] #### Question 8 Which statement best reflects the 2026 catheter-directed thrombolysis evidence? A. The February guideline already incorporated PRAGUE-26 B. HI-PEITHO and PRAGUE-26 were published after the guideline evidence cutoff and suggest reduced early deterioration in selected intermediate-risk patients C. Catheter treatment is now mandatory for every C3 patient D. All catheter devices are clinically interchangeable **Answer: B.** The trials are important emerging evidence but require careful population/device-specific interpretation. [1,15,16] --- ## 22. Current guideline changes and recent research ### STANDARD OF CARE — 2026 multisociety guideline #### New A–E severity categories The 2026 guideline’s most visible conceptual change is replacement of broad low/intermediate/high-risk terminology with categories that integrate symptoms, clinical severity scores, RV function, biomarkers, respiratory compromise, transient hypotension, and end-organ perfusion. [1,3] #### PERT Multidisciplinary PERT assessment is recommended for patients at increased risk of adverse outcomes (Categories C–E) to improve care delivery. [1,3] #### Anticoagulation - LMWH over UFH when parenteral therapy is required in most eligible patients. - DOAC over VKA for most eligible patients. - Extended anticoagulation for first PE without a major reversible factor and for persistent risk factors when bleeding risk permits. [1] #### Advanced therapy - **E1:** systemic thrombolysis, CDT, MT, and surgical embolectomy are reasonable options depending on patient/center factors. - **D1–D2:** these therapies may be considered. - **A–C2:** routine systemic thrombolysis is harmful; routine advanced catheter/surgical treatment is not supported. - **C3:** evidence for routine advanced reperfusion remained uncertain in the guideline. [1,3] #### Follow-up Screen for post-PE symptoms and functional limitation for at least one year; evaluate persistent dyspnea for CTEPD/CTEPH. [1,3] --- ### EMERGING EVIDENCE — HI-PEITHO (2026) HI-PEITHO randomized **544** selected intermediate-risk PE patients with RV/LV ratio ≥1.0, elevated troponin, and at least two indicators of cardiorespiratory distress to ultrasound-facilitated catheter-directed fibrinolysis plus anticoagulation or anticoagulation alone. [15] The primary composite of PE-related death, cardiorespiratory decompensation/collapse, or symptomatic recurrent PE occurred in **4.0% vs 10.3%**. The benefit was driven mainly by less clinical deterioration; major bleeding was numerically higher but not statistically different, and no intracranial hemorrhage occurred in either group. [15] #### Interpretation This trial lowers the threshold for discussing CDT in **carefully selected higher-severity normotensive PE**, but it does not prove that every patient with RV strain should undergo an intervention. The population was highly selected, and results should not be generalized to every catheter device or lower-risk PE. [15] --- ### EMERGING EVIDENCE — PRAGUE-26 (published August 31, 2026) PRAGUE-26 randomized **558** patients with intermediate-high-risk PE to catheter-directed alteplase thrombolysis plus anticoagulation or anticoagulation alone. [16] The 7-day composite of death, recurrent PE, or cardiorespiratory decompensation/collapse occurred in: - **0.7%** with catheter-directed thrombolysis - **6.8%** with standard care - RR **0.10** (95% CI 0.02–0.44; P<0.001). [16] The difference was again driven largely by prevention of decompensation. Clinically relevant bleeding was similar (**4.6% vs 5.0%**); major bleeding was **1.4% vs 2.2%**; intracranial hemorrhage occurred in **0.7% vs 0%**. [16] #### Why this matters PRAGUE-26 was published **after** the February 2026 guideline and therefore is not incorporated into its formal recommendations. Along with HI-PEITHO, it substantially strengthens the clinical-outcome evidence for selected catheter-directed thrombolysis in intermediate-high-risk PE. #### What it does not prove - It does not establish catheter treatment as mandatory for all intermediate-risk PE. - It does not establish equivalence across all devices, lytic doses, or center expertise. - It does not eliminate intracranial or major bleeding risk. - Mortality benefit remains less certain than reduction in deterioration. A future guideline update may change the formal category-C recommendations. --- ### EXPERIMENTAL / INVESTIGATIONAL Areas still requiring stronger evidence include: - selecting the exact C2/C3 phenotype that gains net benefit from early catheter intervention; - head-to-head CDT vs mechanical thrombectomy; - optimal lytic dose and device strategy; - validated biomarkers of impending RV collapse; - long-term effects of acute catheter therapy on post-PE syndrome/CTEPH; - artificial-intelligence–assisted CT triage without compromising clinical judgment. --- ## 23. Guideline differences: 2019 ESC vs 2026 AHA/ACC The 2019 ESC guideline stratifies PE as low risk, intermediate-low, intermediate-high, or high risk using hemodynamic status, PESI/sPESI, RV dysfunction, and troponin. [8] The 2026 AHA/ACC system maps broadly as follows: [3] | 2019 ESC concept | Approximate 2026 AHA/ACC counterpart | |---|---| | Low risk | B (and some A) | | Intermediate-low | C1–C2 | | Intermediate-high | C3 | | Hemodynamic instability/high risk | D–E, with greater granularity for transient hypotension, normotensive shock, established shock, and arrest | They are not perfectly interchangeable. The 2026 model explicitly emphasizes **end-organ perfusion and respiratory modifiers**, allowing earlier recognition of impending failure. --- ## 24. References 1. Creager MA, Barnes GD, Giri J, et al. **2026 AHA/ACC/ACCP/ACEP/CHEST/SCAI/SHM/SIR/SVM/SVN Guideline for the Evaluation and Management of Acute Pulmonary Embolism in Adults.** *J Am Coll Cardiol*. 2026;87(13):1626-1710. doi: **10.1016/j.jacc.2025.11.005**. https://www.jacc.org/doi/10.1016/j.jacc.2025.11.005 2. **Correction: 2026 Acute Pulmonary Embolism Guideline.** *J Am Coll Cardiol*. 2026;88(6):713. Published August 11, 2026. doi: **10.1016/j.jacc.2026.06.033**. https://www.jacc.org/doi/10.1016/j.jacc.2026.06.033 3. Dudzinski DM, Cibotti-Sun M, Moore MM. **2026 Acute Pulmonary Embolism Guideline-at-a-Glance.** *J Am Coll Cardiol*. 2026;87(13):1620-1625. doi: **10.1016/j.jacc.2025.12.023**. 4. Kumbhani DJ, Armbruster AL, Cheng RK, et al. **Direct Oral Anticoagulants in Primary and Secondary Prevention of Thrombotic Events: 2026 ACC Scientific Statement.** *J Am Coll Cardiol*. 2026. doi: **10.1016/j.jacc.2026.05.033**. 5. Righini M, Van Es J, Den Exter PL, et al. **Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism: The ADJUST-UNLIKELY/ADJUST-PE strategy evidence.** *JAMA*. 2014;311:1117-1124. doi: **10.1001/jama.2014.2135**. 6. van der Hulle T, Cheung WY, Kooij S, et al. **Simplified diagnostic management of suspected pulmonary embolism (the YEARS study).** *Lancet*. 2017;390:289-297. doi: **10.1016/S0140-6736(17)30885-1**. 7. Meyer G, Vicaut E, Danays T, et al. **Fibrinolysis for Patients with Intermediate-Risk Pulmonary Embolism (PEITHO).** *N Engl J Med*. 2014;370:1402-1411. doi: **10.1056/NEJMoa1302097**. 8. Konstantinides SV, Meyer G, Becattini C, et al. **2019 ESC Guidelines for the diagnosis and management of acute pulmonary embolism developed in collaboration with the ERS.** *Eur Heart J*. 2020;41:543-603. doi: **10.1093/eurheartj/ehz405**. 9. Agnelli G, Buller HR, Cohen A, et al. **Oral Apixaban for the Treatment of Acute Venous Thromboembolism (AMPLIFY).** *N Engl J Med*. 2013;369:799-808. doi: **10.1056/NEJMoa1302507**. 10. EINSTEIN–PE Investigators. **Oral Rivaroxaban for the Treatment of Symptomatic Pulmonary Embolism.** *N Engl J Med*. 2012;366:1287-1297. doi: **10.1056/NEJMoa1113572**. 11. Schulman S, Kearon C, Kakkar AK, et al. **Dabigatran versus Warfarin in the Treatment of Acute Venous Thromboembolism.** *N Engl J Med*. 2009;361:2342-2352. doi: **10.1056/NEJMoa0906598**. 12. Hokusai-VTE Investigators. **Edoxaban versus Warfarin for the Treatment of Symptomatic Venous Thromboembolism.** *N Engl J Med*. 2013;369:1406-1415. doi: **10.1056/NEJMoa1306638**. 13. Stevens SM, Woller SC, Kreuziger LB, et al. **Antithrombotic Therapy for VTE Disease: Second Update of the CHEST Guideline and Expert Panel Report.** *Chest*. 2021;160:e545-e608. doi: **10.1016/j.chest.2021.07.055**. 14. Kearon C, Akl EA, Ornelas J, et al. **Antithrombotic Therapy for VTE Disease: CHEST Guideline and Expert Panel Report.** *Chest*. 2016;149:315-352. doi: **10.1016/j.chest.2015.11.026**. 15. Rosenfield K, Klok FA, Piazza G, et al; HI-PEITHO Investigators. **Ultrasound-Facilitated, Catheter-Directed Fibrinolysis for Acute Pulmonary Embolism.** *N Engl J Med*. 2026;394(20):1979-1990. doi: **10.1056/NEJMoa2516567**. PMID: **41910345**. 16. Clarençon F, et al. **Catheter-Directed Thrombolysis in Intermediate-High-Risk Pulmonary Embolism (PRAGUE-26).** *N Engl J Med*. Published August 31, 2026. doi: **10.1056/NEJMoa2608012**. 17. Piazza G, et al. **Extended-Duration Low-Intensity Apixaban to Prevent Recurrence in High-Risk Patients With Provoked Venous Thromboembolism (HI-PRO).** *N Engl J Med*. 2025. See ACC ESC 2025 report for trial details. 18. Castellucci LA, Chen VM, Kovacs MJ, et al. **Bleeding Risk with Apixaban vs Rivaroxaban in Acute Venous Thromboembolism (COBRRA).** *N Engl J Med*. 2026;394(11):1051-1060. doi: **10.1056/NEJMoa2510703**. 19. Piazza G, Cushman M. **AHA/ACC Acute Pulmonary Embolism Clinical Categories: Perspectives on Development and Application.** *J Am Coll Cardiol*. 2026;87(13):1554-1557. doi: **10.1016/j.jacc.2025.11.053**. --- ### Bottom line The modern approach to PE is not “diagnose clot and give anticoagulation.” It is a sequence of **probability-based diagnosis, immediate anticoagulation when appropriate, and rapid physiologic risk stratification of the right ventricle and systemic perfusion**. The 2026 AHA/ACC categories make a critical distinction between compensated RV strain and **incipient cardiopulmonary failure**, where early escalation may prevent arrest. Anticoagulation remains the foundation of treatment; advanced reperfusion is standard in shock-level disease and increasingly evidence-supported in carefully selected higher-risk normotensive patients, but treatment must remain individualized to bleeding risk, physiology, anatomy, and local expertise.1a:Tb3af,## One-minute summary **Acute kidney injury (AKI)** is an abrupt decline in kidney function identified by a rise in serum creatinine and/or reduced urine output. The current established international definition remains the **KDIGO 2012 definition**: an increase in serum creatinine by **≥0.3 mg/dL (≥26.5 µmol/L) within 48 hours**, an increase to **≥1.5 times baseline within 7 days**, or urine output **<0.5 mL/kg/hour for 6 hours**.[1] NICE uses equivalent criteria in UK practice.[2] AKI is a **syndrome, not a diagnosis**. Immediate priorities are to identify reversible threats, determine the cause, restore adequate perfusion when appropriate, relieve urinary obstruction, stop or adjust nephrotoxins and renally cleared drugs, manage electrolyte/acid-base/volume complications, and recognize patients who need urgent nephrology or kidney replacement therapy (KRT).[1,2] The classic “prerenal / intrinsic / postrenal” framework is useful, but many patients—especially those with sepsis, heart failure, cirrhosis, major surgery, or shock—have mixed mechanisms. A low fractional excretion of sodium or a bland urine sediment should never override the clinical picture. **Do not dialyze because the creatinine is high.** Initiate KRT urgently for life-threatening complications such as refractory hyperkalemia, severe acid-base disturbance, pulmonary edema/volume overload, or uremic complications; otherwise use the overall clinical trajectory rather than a single creatinine or BUN threshold.[1,6] **Current practice point (2026):** KDIGO has released a **2026 AKI/acute kidney disease (AKD) public-review draft**, but the final guideline has not yet replaced the 2012 standard. New draft concepts—biomarkers, risk models, AKD continuum, updated fluid and KRT guidance—should be considered **emerging until final publication**.[8] --- ## Core concepts ### What AKI represents physiologically Kidney function depends on adequate renal perfusion, intact glomerular filtration, functioning tubular/interstitial tissue, and unobstructed urine flow. AKI can arise from failure at any of these levels and often evolves through several mechanisms at once. A creatinine rise is a **delayed functional marker**: serum creatinine may not increase immediately after injury, and its concentration is influenced by muscle mass, fluid balance, creatinine production, medications that alter tubular secretion, and the baseline kidney reserve. Urine output can change earlier, but oliguria is neither perfectly sensitive nor specific for structural kidney injury.[1] The clinical objective is therefore not merely to “normalize creatinine.” It is to: 1. prevent ongoing injury; 2. preserve oxygen delivery and perfusion; 3. identify treatable causes; 4. prevent lethal electrolyte/volume/acid-base complications; 5. minimize avoidable drug toxicity; 6. recognize transition to persistent AKI/AKD and later CKD. --- ## Definition and KDIGO staging ### Diagnostic criteria AKI is present if **any** of the following occur:[1,2] - serum creatinine rises by **≥0.3 mg/dL (≥26.5 µmol/L) within 48 hours**; - serum creatinine rises to **≥1.5 × baseline**, known or presumed to have occurred within the prior 7 days; - urine output falls to **<0.5 mL/kg/hour for at least 6 hours**. #### KDIGO staging | Stage | Serum creatinine criterion | Urine-output criterion | |---|---|---| | **1** | 1.5–1.9 × baseline **or** rise ≥0.3 mg/dL (≥26.5 µmol/L) | <0.5 mL/kg/h for 6–12 h | | **2** | 2.0–2.9 × baseline | <0.5 mL/kg/h for ≥12 h | | **3** | 3.0 × baseline **or** creatinine ≥4.0 mg/dL (≥353.6 µmol/L) with an acute rise **or** initiation of KRT | <0.3 mL/kg/h for ≥24 h **or** anuria ≥12 h | **Board pearl:** Stage by the **worst criterion** met. A patient can be stage 3 by urine output even if the creatinine rise appears modest. #### Baseline creatinine problems Baseline creatinine may be unknown. Options include: - the most recent reliable pre-illness creatinine; - a stable outpatient value from the preceding months; - adjudication based on prior records and clinical context. Back-calculating a creatinine from an assumed normal eGFR can misclassify patients and should not be treated as a precise substitute for a known baseline. --- ## AKI, AKD, and CKD continuum AKI describes abrupt kidney dysfunction over **≤7 days**. The ADQI framework introduced **acute kidney disease (AKD)** for kidney disease persisting **7–90 days** after an acute initiating event; disease persisting beyond 90 days meets a chronic kidney disease time criterion.[4] This continuum matters because apparent “recovery” from creatinine-defined AKI does not eliminate future risk. AKI survivors have increased risk of recurrent AKI, CKD, cardiovascular events, and death. Post-discharge kidney follow-up is part of AKI care, not an optional afterthought.[1,4] --- ## Epidemiology and prognosis AKI is common across hospital medicine. A large meta-analysis using KDIGO-equivalent definitions found a pooled adult AKI incidence of about **21.6%** during hospital episodes and an associated mortality of about **23.9%**, although rates vary greatly by case mix, geography, and illness severity.[3] ICU cohorts are substantially higher risk; the ADQI consensus summarizes AKI rates around 50% in critical care populations.[4] Severity, duration, recurrence, multiorgan failure, and incomplete recovery all worsen prognosis. Stage 1 AKI is not benign, and repeated “small” creatinine rises can carry meaningful long-term risk. --- ## Risk factors Important risk factors include:[2] - pre-existing CKD, especially eGFR <60 mL/min/1.73 m²; - older age; - diabetes mellitus; - heart failure; - liver disease/cirrhosis; - previous AKI; - sepsis or systemic inflammatory illness; - hypovolemia or hemorrhage; - major or emergency surgery; - urinary tract obstruction or urologic disease; - nephrotoxins or drugs that worsen hemodynamics during acute illness; - recent iodinated contrast exposure in susceptible patients; - hematologic malignancy, tumor lysis, myeloma, or hemolysis/rhabdomyolysis in selected contexts. #### Common medication/exposure contributors | Exposure | Mechanism / concern | Practical response | |---|---|---| | NSAIDs | Afferent arteriolar vasoconstriction; interstitial nephritis | Stop when AKI suspected unless a compelling reason exists | | ACE inhibitor / ARB | Reduces efferent arteriolar tone; can worsen GFR in hypoperfusion, bilateral renal artery stenosis | Review/temporarily hold during significant hypovolemia, shock, vomiting/diarrhea or sepsis; reassess indication when stable | | Diuretics | Can aggravate effective volume depletion; useful for congestion | Do not reflexively stop if patient is markedly congested; treat the physiology | | Aminoglycosides | Tubular toxicity | Avoid if alternatives exist; therapeutic drug monitoring if required | | Vancomycin | AKI risk increases with excessive exposure and other nephrotoxins | Use current AUC/local monitoring strategy; reassess co-nephrotoxins | | Iodinated contrast | Risk is concentrated in selected high-risk patients; causal risk historically overestimated | Do not delay clinically important emergency imaging; use risk-based hydration strategy | | Calcineurin inhibitors | Vasoconstriction and chronic/acute toxicity | Check level/interactions; transplant-nephrology input | | Chemotherapy / targeted agents | Multiple mechanisms: TLS, TMA, interstitial nephritis, tubular injury | Drug-specific evaluation, oncology/nephrology collaboration | **Clinical trap:** “ACE inhibitor + diuretic + NSAID” can be particularly hazardous during dehydration because renal autoregulation and circulating volume are impaired simultaneously. --- ## Etiology: practical classification ### 1. Reduced renal perfusion / hemodynamic AKI Common causes: - hypovolemia: vomiting, diarrhea, hemorrhage, diuresis, burns; - distributive shock/sepsis; - cardiogenic shock or severe low-output heart failure; - advanced cirrhosis with low effective arterial volume; - medications that impair autoregulation in a susceptible patient; - renal artery compromise. Early hemodynamic AKI may be rapidly reversible, but persistent hypoperfusion can progress to tubular injury. ### 2. Intrinsic renal parenchymal injury #### Acute tubular injury (ATI) Common triggers: - ischemia/shock; - sepsis; - major surgery; - nephrotoxins; - pigments (myoglobin/hemoglobin); - prolonged hemodynamic insult. Urine sediment may show **granular “muddy brown” casts** and renal tubular epithelial cells, but their absence does not exclude ATI. #### Acute interstitial nephritis (AIN) Potential causes include: - antibiotics (e.g., beta-lactams, sulfonamides); - proton-pump inhibitors; - NSAIDs; - immune-checkpoint inhibitors; - infections and systemic disease. The classic triad of **fever, rash, eosinophilia** is uncommon; do not require it for diagnosis. #### Glomerular disease Think urgently about glomerulonephritis when AKI is accompanied by: - hematuria; - proteinuria; - red-cell casts/dysmorphic red cells; - hypertension/edema; - systemic inflammatory features (purpura, pulmonary hemorrhage, sinus disease, arthritis, low complement, etc.). #### Vascular causes - thrombotic microangiopathy; - malignant hypertension; - renal infarction/embolism; - atheroembolic disease; - renal vein thrombosis in selected settings. ### 3. Postrenal / obstructive AKI Causes include: - benign prostatic obstruction; - stones; - pelvic/retroperitoneal malignancy; - blood clots; - neurogenic bladder; - urethral obstruction; - bilateral ureteric obstruction; - obstruction of a solitary functioning kidney. Obstruction can occur **without hydronephrosis early** or in dehydration/retroperitoneal fibrosis, so imaging is not infallible. --- ## Initial clinical assessment ### Immediate questions 1. Is the patient unstable? 2. Is there severe hyperkalemia, pulmonary edema, severe acidosis, pericarditis/encephalopathy, or another KRT-level complication? 3. Is the patient volume depleted, congested, or in shock? 4. Could there be urinary obstruction? 5. Is there a nephrotoxin or recent medication change? 6. Does urine/clinical context suggest glomerulonephritis, interstitial nephritis, TMA, myeloma, rhabdomyolysis, or another intrinsic process? --- ## History Focus on: #### Volume and hemodynamic history - oral intake; - vomiting/diarrhea; - fever/sepsis symptoms; - bleeding; - diuretic escalation; - hypotension/syncope; - heart failure symptoms; - cirrhosis/ascites. #### Urinary history - reduced urine volume or anuria; - hesitancy, poor stream, retention; - flank pain/colic; - hematuria; - recent urologic procedure; - pelvic cancer. #### Drug/exposure history - NSAIDs, ACEi/ARB, diuretics; - antibiotics and recent hospitalization; - contrast exposure; - herbal/supplement use; - chemotherapy or immune-checkpoint therapy; - recreational drugs/toxins; - creatine supplements or drugs affecting creatinine secretion. #### Systemic clues - rash/purpura; - arthralgia; - hemoptysis; - sinus disease; - neuropathy; - fever; - weight loss; - muscle pain/immobility/seizure (rhabdomyolysis); - diarrhea followed by anemia/thrombocytopenia (TMA/HUS context). --- ## Examination Assess both **volume depletion and congestion**—they can coexist. #### General and hemodynamic - blood pressure and trend; - heart rate; - capillary refill/peripheral temperature; - mental status; - orthostatic features when safe and relevant. #### Volume status - mucous membranes; - jugular venous pressure; - peripheral edema; - lung crackles; - ascites; - daily weight trend; - bedside ultrasound where expertise exists. #### Cause-specific signs - bladder distention; - flank tenderness; - rash/purpura; - signs of endocarditis; - pulmonary hemorrhage; - severe hypertension with end-organ injury. **Pitfall:** JVP, IVC ultrasound, urine sodium, and physical signs each have limitations. Use converging evidence rather than one “volume status” variable. --- ## Diagnostic workup ### Minimum initial tests in most hospitalized AKI - repeat serum creatinine/urea; - sodium, potassium, bicarbonate; - calcium, phosphate, magnesium as appropriate; - CBC; - urinalysis/dipstick; - urine microscopy when intrinsic disease is possible; - glucose; - ECG if hyperkalemia or arrhythmia risk; - strict urine-output measurement when clinically important. NICE recommends urine dipstick for **blood, protein, leukocytes, nitrites, and glucose** as soon as AKI is suspected or detected.[2] ### Additional tests guided by context | Suspicion | Useful tests | |---|---| | Sepsis | cultures, lactate, source evaluation | | Rhabdomyolysis | CK, phosphate, calcium, urinalysis with heme but few/no RBCs | | Hemolysis/TMA | smear, LDH, haptoglobin, bilirubin, platelets, ADAMTS13 when indicated | | Glomerulonephritis | urine microscopy, urine protein quantification, C3/C4, ANA, ANCA, anti-GBM, hepatitis/HIV tests as context dictates | | Myeloma | serum free light chains, serum/urine electrophoresis/immunofixation | | AIN | medication timeline; eosinophils are nonspecific; biopsy if diagnosis will alter therapy | | Obstruction | bladder scan; renal tract ultrasound or CT depending on suspected level/cause | --- ## Urinalysis and urine microscopy Urine sediment can be one of the highest-yield bedside “kidney biopsies.” | Finding | Suggests | Caveat | |---|---|---| | Muddy brown granular casts / tubular epithelial cells | Acute tubular injury | Sensitivity varies; absence does not exclude ATI | | RBC casts / dysmorphic RBCs | Glomerulonephritis | Urgent nephrology workup | | WBC casts | Interstitial nephritis or pyelonephritis | Not specific | | Heavy proteinuria | Glomerular disease, paraprotein disease | Dipstick underdetects some light chains | | Heme-positive dipstick with few RBCs | Myoglobinuria/hemoglobinuria | Correlate with CK/hemolysis | | Crystals | Drug/crystal nephropathy, uric acid, oxalate | Context determines significance | NICE specifically advises considering acute nephritis and nephrology referral when AKI has no obvious cause and urinalysis shows **hematuria plus proteinuria** without UTI or catheter trauma.[2] --- ## Fractional excretion indices: use cautiously #### FeNa \[ FeNa(\%) = \frac{Urine\ Na \times Plasma\ Cr}{Plasma\ Na \times Urine\ Cr}\times 100 \] A low FeNa can occur in reduced effective circulating volume, but also in: - early sepsis; - contrast-associated AKI; - pigment nephropathy; - glomerulonephritis; - hepatorenal physiology; - some obstructive states. A high FeNa can occur with diuretics, CKD, or established tubular injury. #### FeUrea Sometimes used when diuretics confound FeNa, but FeUrea is also imperfect and should not be treated as a diagnostic truth test. **Board pearl:** The distinction between “prerenal azotemia” and “ATN” is not reliably made by one urine index. --- ## Imaging ### Renal tract ultrasound Use when obstruction is possible or the cause is unclear. NICE advises **immediate ultrasound (within 6 hours)** when pyonephrosis/infected obstruction is suspected.[2] Do not routinely order ultrasound if the cause is already clear and obstruction is not clinically plausible.[2] ### CT Useful when stone disease, retroperitoneal pathology, vascular disease, trauma, or another abdominal cause is suspected. **Do not withhold or delay emergency contrast imaging when delay is likely to be clinically harmful.** NICE’s 2024 update emphasizes that contrast-associated AKI risk is small but increased when eGFR is <30 mL/min/1.73 m² and specifically advises not delaying emergency iodinated contrast when the clinical cost of delay is significant.[2] --- ## Differential diagnosis by pattern | Pattern | Leading possibilities | Clues that shift probability | |---|---|---| | Oliguria after vomiting/diarrhea | Hypovolemia, ATI if prolonged | Orthostasis, low JVP, hemoconcentration, response to cautious fluid | | AKI + edema + pulmonary congestion | Cardiorenal syndrome, GN, renal failure with volume overload | JVP, BNP context, echo, urine sediment, proteinuria | | AKI + hematuria + proteinuria | GN, vasculitis, anti-GBM, infection-related GN | RBC casts, systemic features, complement/serologies | | AKI + thrombocytopenia + hemolysis | TMA/TTP/HUS, malignant HTN | Schistocytes, LDH, haptoglobin, BP, ADAMTS13 context | | AKI + very high CK | Rhabdomyolysis | Muscle injury, dark urine, heme-positive dipstick without RBCs | | AKI + eosinophilia/rash after new drug | AIN | Often lacks classic triad; biopsy may be needed | | AKI + anuria/retention | Obstruction until proven otherwise | Bladder scan, ultrasound/CT | | AKI in cirrhosis | Volume depletion, sepsis, ATI, hepatorenal syndrome, drugs | Diagnose HRS only after excluding/treating competing causes | --- ## Management: stepwise approach ### STEP 1 — Stabilize life-threatening complications Address ABC problems first. In AKI, immediate threats include: - severe hyperkalemia; - pulmonary edema with respiratory compromise; - severe metabolic acidosis; - uremic pericarditis/encephalopathy; - severe symptomatic sodium disturbance; - toxin accumulation where extracorporeal removal is indicated. ### STEP 2 — Treat the cause Examples: - hypovolemia → judicious isotonic crystalloid/blood as appropriate; - hemorrhage → hemorrhage control + blood-product strategy; - sepsis → prompt infection/source control and hemodynamic management; - obstruction → catheterization, nephrostomy, stent, or urologic decompression according to level/cause; - GN/vasculitis/TMA → urgent disease-specific specialist pathway; - rhabdomyolysis → early fluids when appropriate, treat cause, monitor potassium/calcium/phosphate; - drug toxicity → stop culprit, adjust doses, antidote/extracorporeal therapy when indicated. ### STEP 3 — Stop ongoing kidney insults - stop nonessential nephrotoxins; - review ACEi/ARB, NSAIDs, diuretics and SGLT2 inhibitors in context rather than by rote; - adjust doses of renally cleared drugs; - avoid duplicate contrast/nephrotoxin exposure where clinically unnecessary; - check drug interactions and levels where relevant. ### STEP 4 — Optimize volume and perfusion KDIGO favors **isotonic crystalloids rather than colloids** for initial intravascular volume expansion in patients at risk of or with AKI when hemorrhagic shock is absent.[1] #### Balanced crystalloid vs 0.9% saline In the SMART trial, balanced crystalloids modestly reduced the composite of death, new KRT, or persistent renal dysfunction compared with saline in critically ill adults (14.3% vs 15.4%).[5] This supports frequent use of balanced crystalloid in many critically ill patients, but fluid choice must account for the indication, electrolyte/acid-base context, neurologic disease, and local protocol. **Do not give fluid merely because creatinine rose.** If the patient is congested or has cardiogenic physiology, repeated boluses can worsen pulmonary edema and renal venous congestion. ### STEP 5 — Monitor dynamically - urine output; - daily or more frequent creatinine/electrolytes according to severity; - potassium and bicarbonate; - fluid input/output; - daily weight in significant volume disturbance; - hemodynamics; - drug concentrations when indicated; - clinical response to interventions. NICE notes that daily creatinine measurement is typical for hospitalized patients with or at risk of AKI, adjusted to clinical need.[2] --- ## Pharmacotherapy principles ### Diuretics **STANDARD OF CARE:** Do **not** use loop diuretics to prevent AKI or to “convert” oliguric AKI to non-oliguric AKI. They are appropriate for **fluid overload/congestion** when there is a reasonable chance of diuretic response.[1,2] A rise in creatinine during effective decongestion in heart failure does not automatically mean diuretics should be stopped; interpret renal function alongside congestion, perfusion, blood pressure, and overall trajectory. ### Low-dose dopamine Do **not** use low-dose “renal-dose” dopamine to prevent or treat AKI.[1,2] ### ACE inhibitors and ARBs During significant acute volume depletion, vomiting/diarrhea, hypotension, or sepsis, temporary withholding may be reasonable and is specifically suggested by NICE in relevant acute illness.[2] However, once the acute process resolves, **reassess and restart evidence-based indications** rather than allowing accidental permanent discontinuation. --- ## Emergency hyperkalemia in AKI Hyperkalemia is one of the most important immediately reversible causes of death in severe AKI. #### First actions - confirm the result rapidly if pseudohyperkalemia is plausible, **without delaying treatment** when the patient is unstable or ECG changes are present; - obtain a 12-lead ECG and continuous monitoring for severe hyperkalemia; - stop exogenous potassium and contributing drugs; - stabilize the myocardium when ECG toxicity is present; - shift potassium intracellularly; - remove potassium from the body; - repeat potassium and glucose because rebound and hypoglycemia are common. #### UK Kidney Association 2023 adult emergency doses | Purpose | Treatment | Adult dose / note | |---|---|---| | **Protect the heart** | 10% calcium chloride | **10 mL IV over 5 min** in peri-arrest/cardiac arrest or according to local resuscitation protocol | | **Protect the heart** | 10% calcium gluconate | **30 mL IV over 10 min** for other patients with hyperkalemic ECG changes | | **Shift K into cells** | Soluble insulin + glucose | **10 units soluble insulin in 25 g glucose IV** for severe K ≥6.5 mmol/L; consider in moderate K 6.0–6.4 mmol/L | | Prevent post-insulin hypoglycemia | 10% glucose infusion | If pretreatment glucose <7 mmol/L, UKKA recommends **10% glucose 50 mL/hour for 5 h** after insulin-glucose | | **Adjunct shift** | Nebulized salbutamol | **10–20 mg nebulized** as adjunct in severe hyperkalemia; do not use as sole therapy | These doses are from UKKA guidance and may differ by jurisdiction/local resuscitation policy.[7] **Calcium does not lower serum potassium.** It temporarily reduces myocardial excitability risk while potassium-lowering therapy is initiated. **KRT should not be delayed** when severe hyperkalemia is refractory or expected to recur rapidly because of advanced renal failure, ongoing tissue breakdown, or inability to remove potassium medically.[1,7] --- ## Metabolic acidosis Treat the cause first: shock, sepsis, ketoacidosis, toxin, renal failure, etc. Sodium bicarbonate is **not a universal AKI therapy**. Consider it selectively when severe acidemia itself is harmful and bicarbonate therapy is physiologically appropriate, while avoiding sodium/volume overload and recognizing that severe refractory acidosis may require KRT. --- ## Kidney replacement therapy (KRT) ### Indications KDIGO recommends emergency KRT when there are **life-threatening changes in fluid, electrolyte, or acid-base balance**.[1] Common practical indications include: - refractory severe hyperkalemia; - refractory severe metabolic acidosis; - refractory pulmonary edema/volume overload causing hypoxemia; - uremic pericarditis; - uremic encephalopathy or severe symptomatic uremia; - selected dialyzable intoxications; - progressive complications when medical management is failing. #### What should NOT determine KRT alone - one creatinine value; - one BUN/urea value; - oliguria in isolation; - “stage 3 AKI” without clinical context. ### Timing when no emergency indication exists The **STARRT-AKI** trial randomized critically ill patients with severe AKI to accelerated vs standard KRT initiation. Accelerated initiation **did not reduce 90-day mortality** and was associated with more adverse events and greater dialysis dependence among survivors.[6] **STANDARD OF CARE implication:** In a patient without an urgent indication, do not start KRT solely because severe AKI has developed. Watch the clinical trajectory closely and start when complications, worsening physiology, or failure of conservative management justify it. ### Modality - **Intermittent hemodialysis:** efficient solute/volume removal; may be poorly tolerated in unstable patients. - **Continuous KRT (CKRT/CRRT):** often favored in severe hemodynamic instability or some neurocritical-care situations. - **Prolonged intermittent therapies (SLED/PIRRT):** hybrid option depending on local resources. Modality should reflect hemodynamics, neurologic status, solute-removal needs, staffing/resources, and local expertise—not an assumption that one modality is universally superior. --- ## Contrast-associated AKI: 2024 practice update NICE updated its iodinated-contrast recommendations in **October 2024**.[2] #### Key points - An **eGFR <30 mL/min/1.73 m²** is associated with a small but increased risk of AKI from iodinated contrast exposure. - **Do not delay emergency contrast imaging** if delaying contrast is likely to cause clinically significant harm. - For increased-risk patients, encourage **oral hydration** before and after IV iodinated contrast when appropriate. - For particularly high-risk inpatients (e.g., eGFR <30, kidney transplant, high contrast volume/repeat dose, first-pass intra-arterial exposure), consider IV volume expansion with **0.9% saline or isotonic sodium bicarbonate**. - NICE suggests considering temporary ACEi/ARB withholding in CKD with eGFR <30 around iodinated contrast. **Guideline conflict / nuance:** Contrast protocols differ among radiology, nephrology, and national guidance. Modern evidence has reduced previous estimates of contrast-caused AKI, especially for routine IV CT. The clinical harm of missing or delaying a time-critical diagnosis can exceed the renal risk. Use local radiology policy and patient-specific risk rather than a blanket “no contrast in AKI” rule. --- ## When to involve nephrology urgently NICE recommends discussion with nephrology within 24 hours when there is, among other situations:[2] - stage 3 AKI; - AKI with no clear cause; - inadequate response to treatment; - complications of AKI; - suspected vasculitis, glomerulonephritis, interstitial nephritis, or myeloma requiring specialist therapy; - kidney transplant; - advanced CKD (stage 4–5). **Immediate** nephrology/critical-care discussion is needed for potential KRT indications or severe rapidly evolving complications. --- ## Special clinical contexts ### Sepsis-associated AKI Mechanisms extend beyond simple “renal hypoperfusion” and include inflammatory, endothelial, microcirculatory, venous-congestion, and tubular-metabolic changes. Management centers on: - source control and antimicrobials; - hemodynamic resuscitation; - avoiding both under-resuscitation and fluid overload; - dose-adjusting renally cleared antimicrobials; - KRT when indicated. ### Heart failure / cardiorenal syndrome Creatinine can worsen from low forward flow, high venous pressure, neurohormonal activation, or treatment-related hemodynamic changes. In a clearly congested patient, blindly giving fluid because of AKI can be dangerous. Decongestion often remains necessary. ### Cirrhosis Consider: - hypovolemia/bleeding; - sepsis; - acute tubular injury; - nephrotoxins; - abdominal compartment physiology; - hepatorenal syndrome (HRS-AKI). HRS is a diagnosis requiring appropriate exclusion/treatment of competing causes; early hepatology/nephrology involvement is appropriate. ### Rhabdomyolysis - treat the cause; - give isotonic fluid early when appropriate and not volume-overloaded; - monitor potassium, calcium, phosphate, bicarbonate, CK and urine output; - do not use bicarbonate or mannitol routinely solely to prevent AKI without a specific indication; - dialyze for standard complications, not CK level alone. ### Pregnancy AKI requires obstetric-nephrology evaluation. Important causes include hemorrhage, sepsis, hyperemesis, preeclampsia/HELLP, acute fatty liver of pregnancy, TMA, cortical necrosis, and obstruction. Normal pregnancy creatinine is lower than in nonpregnant adults, so a “normal-range” creatinine may already represent significant renal dysfunction. ### Kidney transplant AKI differentials include rejection, obstruction, vascular complications, infection, volume/hemodynamic causes, calcineurin-inhibitor toxicity, and drug interactions. Involve the transplant team early. --- ## Prevention ### General prevention bundle For high-risk patients: - identify CKD and previous AKI; - monitor creatinine and urine output appropriately; - maintain adequate perfusion and avoid unnecessary hypotension; - avoid or minimize nephrotoxins; - use drug-dose adjustment and therapeutic monitoring; - avoid unnecessary contrast repetition; - prevent/treat sepsis promptly; - prevent severe dehydration; - use protocolized perioperative risk management when indicated. NICE recommends active AKI risk assessment in acutely ill adults with CKD, heart failure, liver disease, diabetes, prior AKI, oliguria, hypovolemia, sepsis, recent nephrotoxin exposure, obstruction risk, deteriorating early-warning scores, or age ≥65 years.[2] --- ## Monitoring and reassessment ### In-hospital Track: - urine output hourly when severe/unstable; - creatinine and electrolytes at a frequency dictated by trajectory; - potassium more frequently after emergency therapy; - bicarbonate/pH when acid-base disturbance is important; - daily weights and fluid balance in major volume disturbance; - drug levels where required; - nutritional status; - recovery vs persistent AKI. ### After discharge KDIGO recommends evaluating patients **3 months after AKI** for resolution, new CKD, or worsening pre-existing CKD.[1] NICE advises post-AKI creatinine monitoring based on stability at discharge and considering nephrology referral when eGFR is **≤30 mL/min/1.73 m²** after recovery.[2] Practical follow-up should also address: - blood pressure; - albuminuria/proteinuria where appropriate; - medication reconciliation and restart of indicated drugs; - recurrent AKI prevention; - avoidance of unnecessary NSAIDs; - cardiovascular/CKD risk management. --- ## Anticipating deterioration | Warning sign | Why it matters | Immediate response | |---|---|---| | Rapidly rising K or ECG changes | Arrhythmic death | Cardiac protection + K shift/removal + nephrology/KRT planning | | Falling urine output → anuria | Severe AKI or obstruction | Check catheter/bladder, hemodynamics, imaging, obstruction | | Rising O2 requirement + edema | Pulmonary edema/volume overload | Respiratory support, diuresis if responsive, KRT if refractory | | New confusion, pericarditic pain/rub | Uremic complication | Urgent nephrology/KRT assessment | | Hematuria + proteinuria + systemic features | Rapidly progressive GN | Serologies + urgent nephrology; biopsy/immunotherapy pathway | | Thrombocytopenia + hemolysis | TMA | Immediate hematology/nephrology pathway | | Severe hypertension + AKI | Malignant HTN/TMA | Controlled BP reduction, end-organ assessment | | Persistent AKI >7 days | AKD transition | Reassess diagnosis, nephrotoxins, obstruction, biopsy need, follow-up plan | --- ## Common pitfalls | Pitfall | Why it fails | Better approach | |---|---|---| | Calling every creatinine rise “dehydration” | Misses congestion, GN, obstruction, TMA, ATI | Establish physiology and cause | | Giving repeated fluids without reassessment | Can worsen pulmonary edema and venous congestion | Give fluid only for a plausible fluid-responsive state and reassess | | Relying on FeNa alone | Many false-low and false-high states | Integrate history, exam, urine sediment, hemodynamics | | Using diuretics to “treat the creatinine” | Does not reverse renal injury | Use for clinically important volume overload | | Waiting for severe creatinine before checking urine | Delays GN/obstruction clues | Early urinalysis and sediment | | Refusing emergency contrast because of AKI | Can delay diagnosis of PE, aortic catastrophe, bleeding, stroke pathway, etc. | Weigh diagnostic harm vs renal risk; emergency imaging often proceeds | | Dialyzing by BUN/creatinine threshold | Ignores actual indication and trial evidence | Dialyze for physiology/complications/trajectory | | Forgetting medication restart after recovery | Permanent loss of beneficial ACEi/ARB/other therapy | Reconcile and restart when safe | | Discharging without follow-up | Misses AKD/CKD and recurrence risk | Define post-AKI kidney monitoring | --- ## Diagnostic and management algorithm ```text Creatinine rise and/or oliguria meets AKI criteria ↓ 1. Confirm trend + assess severity - K, bicarbonate/pH, oxygenation, volume status, urine output ↓ 2. Any immediate life threat? - severe hyperK / pulmonary edema / severe acidosis / uremic complication ├─ YES → emergency treatment + nephrology/critical care + consider KRT └─ NO ↓ 3. Search for reversible cause - hypovolemia/shock? - congestion/heart failure? - obstruction? - nephrotoxin/drug? - sepsis? - GN/AIN/TMA/rhabdo/myeloma? ↓ 4. Core tests - urinalysis + sediment - electrolytes/CBC - bladder scan/ultrasound if obstruction plausible - targeted serology/CK/hemolysis tests as indicated ↓ 5. Treat cause + optimize perfusion/volume - fluid only if appropriate - decongest if overloaded - relieve obstruction - stop/adjust nephrotoxins ↓ 6. Reassess repeatedly - creatinine trend, urine output, K, acid-base, volume status ↓ 7. Persistent/worsening AKI, stage 3, unclear cause, or complications? ├─ YES → nephrology; consider biopsy/KRT └─ NO → continue cause-directed management ↓ 8. Discharge only with recovery trajectory + medication plan + kidney follow-up ``` --- ## STANDARD OF CARE vs EMERGING EVIDENCE vs EXPERIMENTAL ### STANDARD OF CARE - KDIGO creatinine/urine-output diagnosis and staging.[1] - Cause-directed treatment and repeated clinical reassessment. - Isotonic crystalloid for true intravascular volume depletion, avoiding indiscriminate fluid loading.[1] - Stop/adjust nephrotoxins and renally cleared drugs. - Do not use low-dose dopamine.[1,2] - Do not use loop diuretics to prevent/treat AKI except to manage volume overload.[1,2] - Urgent KRT for life-threatening electrolyte, acid-base, volume, or uremic complications.[1] - Do not start KRT solely because a creatinine/BUN threshold has been reached.[1,6] - Post-AKI follow-up for CKD/AKD risk.[1,4] ### EMERGING EVIDENCE / ACTIVE IMPLEMENTATION - Biomarker-supported risk stratification (e.g., tubular-stress/injury biomarkers) in selected settings. - Electronic AKI prediction and decision-support systems. - More formal AKI-to-AKD transition pathways and structured post-discharge clinics. - Precision fluid/hemodynamic strategies using dynamic responsiveness and congestion measures. - Broader integration of nephrotoxin stewardship programs. ### EXPERIMENTAL / NOT ROUTINE FOR GENERAL AKI - Using a novel biomarker alone to diagnose the cause of AKI or decide KRT. - “Renal-protective” pharmacologic agents without proven patient-centered benefit. - Routine extracorporeal therapy solely to remove inflammatory mediators in sepsis-associated AKI outside established indications/trials. --- ## Current guideline changes and conflicts (2024–2026) ### 1. Contrast-associated AKI risk has been reframed NICE 2024 now emphasizes an increased risk mainly at **eGFR <30**, uses updated terminology “contrast-associated AKI,” and explicitly warns against delaying clinically important emergency contrast imaging.[2] ### 2. KDIGO AKI update is imminent but not final KDIGO released a **2026 public-review draft** covering AKI and AKD, expanded biomarkers/risk prediction, fluids/hemodynamics, nephrotoxin stewardship, contrast-associated AKI, KRT timing/modality/dose/discontinuation, and follow-up.[8] Until final publication, the 2012 guideline remains the formal KDIGO standard. ### 3. Early routine KRT has lost momentum STARRT-AKI provides strong evidence against automatic accelerated KRT in severe AKI without urgent complications.[6] ### 4. Balanced crystalloids increasingly favored in many acute-care pathways SMART demonstrated a modest kidney-centered composite benefit compared with saline in critically ill adults.[5] Fluid composition remains context-dependent rather than absolute. --- ## Landmark and practice-shaping evidence ### SMART (2018) 15,802 critically ill adults were randomized in a pragmatic cluster-crossover design. Major adverse kidney events within 30 days occurred in **14.3%** with balanced crystalloids vs **15.4%** with saline (P=0.04).[5] **Takeaway:** A small absolute benefit supports balanced crystalloid as a reasonable default in many critically ill adults, but effect size is modest and context matters. ### STARRT-AKI (2020) Nearly 3000 critically ill patients with severe AKI were assigned to accelerated or standard KRT initiation. Accelerated KRT did **not** reduce 90-day mortality; adverse events were more frequent, and KRT dependence among survivors was higher.[6] **Takeaway:** In the absence of emergency indications, clinical watchfulness is often preferable to automatic early dialysis. ### AKI–AKD continuum (ADQI) The ADQI consensus formalized AKD as kidney disease persisting 7–90 days after an acute event, emphasizing that kidney recovery is a trajectory, not a binary discharge diagnosis.[4] --- ## Exam-focused review ### USMLE Step 1 Know: - afferent vs efferent arteriolar physiology; - how NSAIDs and ACEi/ARB can reduce GFR under vulnerable hemodynamic conditions; - tubular injury and muddy brown casts; - glomerular hematuria/RBC casts; - obstruction physiology; - why creatinine lags behind true GFR decline. ### USMLE Step 2 CK Prioritize: - volume status and cause; - urinalysis/sediment; - ultrasound when obstruction is possible; - stopping nephrotoxins; - treating hyperkalemia and pulmonary edema before “workup completion.” ### Step 3 / Resident Focus on: - mixed hemodynamic + structural AKI; - drug dosing and restart plans; - when fluid is harmful; - nephrology referral; - KRT indications vs timing; - post-AKI follow-up. ### MRCP / ABIM / Boards High-yield discriminators: - low FeNa is not synonymous with prerenal AKI; - loop diuretics do not improve AKI recovery; - stage can be determined by urine output; - emergency contrast should not be reflexively withheld; - dialysis is based on complications/trajectory, not a creatinine number; - hematuria + proteinuria + AKI should trigger GN thinking; - thrombocytopenia + hemolysis + AKI should trigger TMA thinking. --- ## Original MCQs ### Question 1 A 72-year-old man with vomiting and diarrhea has a creatinine rise from 1.0 to 1.4 mg/dL within 36 hours. Urine output is preserved. Which statement is most accurate? A. He does not have AKI because creatinine is <2 mg/dL B. He has KDIGO stage 1 AKI C. He has stage 2 AKI D. AKI requires oliguria E. AKI can only be diagnosed after 7 days **Answer: B.** A rise ≥0.3 mg/dL within 48 hours meets AKI criteria and stage 1 severity.[1] --- ### Question 2 A patient with severe decompensated heart failure, pulmonary edema, high JVP, and worsening creatinine receives repeated 1-L saline boluses because the creatinine is rising. Which is the best critique? A. All AKI should receive at least 3 L crystalloid B. Rising creatinine proves intravascular depletion C. Fluid can worsen venous congestion and pulmonary edema; volume therapy should follow physiology D. Diuretics are contraindicated in all AKI E. Dialysis should be started based on creatinine alone **Answer: C.** AKI in heart failure may reflect congestion and low effective perfusion; indiscriminate fluid can worsen both respiratory status and renal venous pressure. --- ### Question 3 A patient with AKI has potassium 7.0 mmol/L, a widened QRS, and no dialysis catheter. What is the immediate priority? A. Wait for repeat potassium before treatment B. Give IV calcium to stabilize the myocardium while initiating potassium-lowering therapy C. Give furosemide only D. Start oral sodium bicarbonate and review tomorrow E. Obtain renal biopsy **Answer: B.** Hyperkalemic ECG toxicity is immediately life-threatening. Calcium protects the myocardium but does not lower K; simultaneous shift/removal therapy and urgent nephrology/KRT planning are required.[7] --- ### Question 4 A critically ill patient has KDIGO stage 3 AKI but potassium, pH, oxygenation, and volume status are controlled. Which statement best reflects modern evidence? A. Stage 3 AKI mandates immediate dialysis in all patients B. Creatinine >3× baseline mandates dialysis C. Accelerated KRT improves 90-day mortality D. In the absence of urgent indications, KRT timing should be individualized and close monitoring is appropriate E. KRT should be withheld even if refractory hyperkalemia develops **Answer: D.** STARRT-AKI found no mortality benefit from accelerated KRT in severe AKI without urgent indications.[6] --- ### Question 5 A 69-year-old with AKI has hematuria, proteinuria, pulmonary infiltrates, and falling hemoglobin. What should be prioritized? A. Diagnose prerenal AKI from FeNa alone B. Assume contrast nephropathy C. Urgent evaluation for pulmonary-renal vasculitis/anti-GBM disease with nephrology involvement D. Give NSAIDs for pleuritic pain E. Wait for spontaneous recovery **Answer: C.** AKI with an active urine sediment and pulmonary hemorrhage features is a nephrologic emergency. --- ### Question 6 A hemodynamically stable patient with suspected aortic dissection has AKI and eGFR 24 mL/min/1.73 m². CT angiography is urgently needed. Which is the best approach? A. Delay contrast for several days until creatinine normalizes B. Cancel definitive imaging because eGFR is <30 C. Proceed with time-critical contrast imaging while using appropriate renal-risk mitigation D. Give N-acetylcysteine and postpone imaging E. Dialyze prophylactically before CT **Answer: C.** NICE 2024 explicitly states not to delay emergency iodinated contrast when the risk of delay is clinically significant.[2] --- ## Acute management checklist ### Recognition - [ ] Compare creatinine with baseline and stage AKI. - [ ] Measure and trend urine output. - [ ] Check K, bicarbonate/pH, volume status, oxygenation. - [ ] Obtain urinalysis early. ### Immediate threats - [ ] ECG if hyperkalemia suspected/severe. - [ ] Treat hyperkalemic ECG toxicity immediately. - [ ] Treat pulmonary edema and severe acidosis. - [ ] Call nephrology/critical care early for KRT-level complications. ### Cause - [ ] Assess hypovolemia vs congestion vs shock. - [ ] Review all medications and recent exposures. - [ ] Check for urinary obstruction. - [ ] Screen for GN/AIN/TMA/rhabdo/myeloma when context suggests. ### Management - [ ] Give isotonic crystalloid only when a fluid-responsive state is plausible. - [ ] Stop/adjust nephrotoxins and renally cleared drugs. - [ ] Treat infection/bleeding/obstruction/cardiac cause. - [ ] Use diuretics for congestion, not to “cure AKI.” - [ ] Reassess after every major intervention. ### Discharge - [ ] Document AKI episode and peak stage. - [ ] Define creatinine/electrolyte follow-up. - [ ] Reconcile temporarily held medications. - [ ] Assess CKD/albuminuria/BP risk. - [ ] Educate regarding dehydration and NSAID/nephrotoxin risk. --- ## References 1. **Kidney Disease: Improving Global Outcomes (KDIGO) Acute Kidney Injury Work Group.** KDIGO Clinical Practice Guideline for Acute Kidney Injury. *Kidney Int Suppl.* 2012;2:1-138. Official guideline: https://kdigo.org/guidelines/acute-kidney-injury/ 2. **National Institute for Health and Care Excellence (NICE).** Acute kidney injury: prevention, detection and management. NG148. Published 2019; updated 16 October 2024. https://www.nice.org.uk/guidance/ng148 3. **Susantitaphong P, Cruz DN, Cerda J, et al.** World incidence of AKI: a meta-analysis. *Clin J Am Soc Nephrol.* 2013;8(9):1482-1493. PMID: 23744003. doi:10.2215/CJN.00710113 4. **Chawla LS, Bellomo R, Bihorac A, et al.; ADQI 16 Workgroup.** Acute kidney disease and renal recovery: consensus report of the Acute Disease Quality Initiative (ADQI) 16 Workgroup. *Nat Rev Nephrol.* 2017;13:241-257. doi:10.1038/nrneph.2017.2 5. **Semler MW, Self WH, Wanderer JP, et al.; SMART Investigators.** Balanced Crystalloids versus Saline in Critically Ill Adults. *N Engl J Med.* 2018;378:829-839. doi:10.1056/NEJMoa1711584 6. **STARRT-AKI Investigators.** Timing of Initiation of Renal-Replacement Therapy in Acute Kidney Injury. *N Engl J Med.* 2020;383:240-251. doi:10.1056/NEJMoa2000741 7. **Alfonzo A, Harrison A, Baines R, Chu A, Mann S, MacRury M.** UK Kidney Association Clinical Practice Guideline: Management of Hyperkalaemia in Adults. Published 19 December 2023. https://www.ukkidney.org/health-professionals/guidelines/treatment-acute-hyperkalaemia-adults-0 8. **Kidney Disease: Improving Global Outcomes (KDIGO).** Acute Kidney Injury (AKI) and Acute Kidney Disease (AKD): 2026 Guideline Public Review information. Public review closed 11 May 2026; final guideline pending at time of review. https://kdigo.org/guidelines/acute-kidney-injury/ --- ### NEXT-TOPIC LEDGER **Completed today:** Acute Kidney Injury **Do not repeat normalized title:** `acute-kidney-injury` **Suggested future linked topics:** Acute kidney disease; Chronic kidney disease; Hyperkalemia; Glomerulonephritis; Acute interstitial nephritis; Rhabdomyolysis; Kidney replacement therapy; Contrast-associated AKI1b:T76cc,## One-minute summary **Acute coronary syndrome (ACS)** is the clinical spectrum caused most often by acute coronary atherothrombosis after plaque rupture or erosion and includes **ST-elevation myocardial infarction (STEMI), non-ST-elevation myocardial infarction (NSTEMI), and unstable angina (UA)**. Modern care is built around five simultaneous priorities: **recognize ischemia, obtain/interpret a 12-lead ECG rapidly, use high-sensitivity cardiac troponin serially, start evidence-based antithrombotic/anti-ischemic therapy, and choose the correct revascularization strategy without delay**.[1–4] The 2025 ACC/AHA/ACEP/NAEMSP/SCAI ACS guideline emphasizes DAPT, radial access for PCI, intravascular imaging for PCI guidance, complete revascularization in appropriate multivessel disease, prompt revascularization in cardiogenic shock, intensive lipid lowering, and cardiac rehabilitation.[1,2] The 2023 ESC ACS guideline similarly integrates STEMI and NSTE-ACS in one pathway and stresses high-sensitivity troponin algorithms and time-sensitive invasive care.[3] ### Immediate priorities 1. **ABCs + monitor + IV access**; treat shock, malignant arrhythmia, pulmonary edema, or cardiac arrest first. 2. **12-lead ECG promptly** and repeat if symptoms continue or the first tracing is nondiagnostic. 3. **High-sensitivity troponin** with an assay-specific accelerated serial algorithm; do not use a single universal numeric cutoff across assays. 4. **Aspirin immediately** unless true contraindication. 5. Determine whether this is **STEMI/occlusion requiring immediate reperfusion** versus **NSTE-ACS requiring risk-stratified invasive management**. 6. Add a **P2Y12 inhibitor + parenteral anticoagulation** according to the reperfusion/invasive strategy and bleeding risk. 7. Start **high-intensity statin** and secondary prevention early. ★ **High-yield principle:** In suspected ACS, the ECG determines the urgent reperfusion pathway; troponin helps diagnose myocardial injury/infarction but should **not delay reperfusion** for a clear STEMI pattern with an appropriate clinical presentation. --- ## Definition and classification ACS describes acute myocardial ischemia caused predominantly by an unstable atherosclerotic coronary lesion and thrombosis. The 2025 U.S. guideline focuses mainly on **type 1 ACS**, where plaque disruption and coronary thrombosis are the mechanism.[1] | Syndrome | ECG pattern | Troponin | Core concept | |---|---|---|---| | STEMI | Persistent ST elevation or an accepted STEMI-equivalent/occlusion pattern in the right context | Usually rises, but may initially be normal | Acute coronary occlusion or near-occlusion requiring immediate reperfusion | | NSTEMI | No persistent ST elevation; may show ST depression, T-wave inversion, transient elevation, or a nondiagnostic ECG | Rise/fall with ≥1 value above assay-specific 99th percentile plus evidence of ischemia | Myocardial infarction without classic persistent ST elevation | | Unstable angina | No persistent ST elevation | No biomarker evidence meeting MI criteria | Ischemic symptoms without detectable acute myocardial necrosis; less common in the high-sensitivity troponin era | ### Myocardial injury is not automatically myocardial infarction Troponin elevation means **myocardial injury**, not necessarily ACS. MI requires acute myocardial injury plus evidence of ischemia. Important alternative causes include sepsis, tachyarrhythmia, myocarditis, pulmonary embolism, acute heart failure, severe anemia, renal disease with dynamic injury, and supply-demand mismatch (type 2 MI). --- ## Pathophysiology The usual sequence is: **lipid-rich atherosclerotic plaque → plaque rupture or endothelial erosion → platelet adhesion/activation → thrombin generation → fibrin-rich thrombus → abrupt reduction in coronary blood flow → myocardial ischemia → myocyte necrosis if ischemia persists.** Ischemia begins subendocardially because wall stress and perfusion vulnerability are highest there. With sustained complete occlusion, necrosis can progress toward the epicardium. Infarct size is influenced by occlusion duration, collateral supply, myocardial oxygen demand, ischemic preconditioning, reperfusion timing, and microvascular obstruction. ### STEMI vs NSTEMI is an ECG phenotype, not a complete anatomy report Some acute coronary occlusions do not produce classic ST elevation. Conversely, ST elevation can be caused by pericarditis, early repolarization, left ventricular aneurysm, Takotsubo syndrome, electrolyte disorders, and other mimics. Clinical reasoning and serial ECGs matter. --- ## Risk factors Major atherosclerotic risk factors include: - Age and family history of premature ASCVD - Cigarette smoking - Hypertension - Diabetes mellitus - Dyslipidemia - Chronic kidney disease - Obesity and physical inactivity - Established coronary, cerebrovascular, or peripheral arterial disease - Chronic inflammatory disease Additional precipitants or modifiers include cocaine/amphetamine exposure, severe emotional or physiologic stress, acute infection, anemia, uncontrolled hypertension, and perioperative stress. --- ## Clinical presentation ### Typical ischemic symptoms - Retrosternal pressure, heaviness, squeezing, burning, or tightness - Radiation to arm(s), shoulder, neck, jaw, back, or epigastrium - Dyspnea - Diaphoresis - Nausea/vomiting - Sense of impending doom - Symptoms provoked by exertion and persistent at rest in acute presentations ### Atypical or less obvious presentations Older adults, women, and patients with diabetes or CKD may present with: - Dyspnea without prominent pain - Weakness or fatigue - Syncope/presyncope - Nausea or epigastric discomfort - Acute heart failure - Confusion Do not dismiss ACS because pain is described as “burning,” “indigestion,” or is not left-sided. ### Red flags for immediate instability - Hypotension, cool extremities, altered mentation - Ongoing severe chest pain despite initial therapy - Ventricular tachycardia/fibrillation - High-grade AV block or severe bradycardia - Acute pulmonary edema - Mechanical complication murmur - Recurrent dynamic ST changes - Cardiac arrest --- ## Initial assessment: first 10 minutes ### Core workflow | Component | Assessment | Interpretation | Immediate action | Anticipate deterioration | |---|---|---|---|---| | Airway/Breathing | Work of breathing, SpO₂, lung exam | Pulmonary edema, hypoxemia, alternative diagnosis | Oxygen only when clinically indicated; ventilatory support if needed | Acute LV failure, respiratory fatigue | | Circulation | HR, BP, perfusion, pulses, JVP | Shock, RV infarction, mechanical complication, arrhythmia | Monitor, IV access, cautious fluids if appropriate, shock pathway | Cardiogenic shock, VT/VF, AV block | | ECG | 12-lead ECG; right/posterior leads when indicated | STEMI/occlusion, ischemia, alternate diagnosis | Activate reperfusion pathway when indicated | Dynamic evolution; repeat ECG | | Biomarkers | hs-cTn serially | Acute myocardial injury pattern | Use validated assay-specific algorithm | Early presenters may have initially normal value | | History | Onset, quality, duration, bleeding history, anticoagulants, PDE5 inhibitors, prior stroke/TIA, allergy | Determines differential and treatment safety | Do not delay reperfusion for exhaustive history | Bleeding, medication contraindications | #### ECG Obtain a 12-lead ECG as early as possible in suspected ACS. Repeat ECGs if symptoms persist or recur, and consider: - **Right-sided leads (especially V4R)** for inferior MI with possible RV involvement - **Posterior leads V7–V9** when posterior MI is suspected, e.g., ST depression V1–V3 with a compatible presentation #### High-sensitivity troponin Use the laboratory's validated **high-sensitivity cardiac troponin (hs-cTn)** assay and accelerated serial algorithm. ESC guidance supports 0/1-hour or 0/2-hour pathways with assay-specific thresholds.[3,4] Interpretation requires: - Absolute concentration relative to the assay's 99th percentile - Rise/fall (delta) - Time since symptom onset - Renal function and chronic structural heart disease - Clinical/ECG evidence of ischemia ⚠ **Common trap:** A chronically elevated troponin in CKD does not prove NSTEMI. Look for a dynamic change and ischemic context. --- ### Differential diagnosis of acute chest pain | Diagnosis | Clues favoring diagnosis | Distinguishing test/findings | Immediate hazard | |---|---|---|---| | ACS | Pressure, diaphoresis, dynamic ECG/troponin | Serial ECG + hs-cTn | Arrhythmia, infarction, shock | | Aortic dissection | Abrupt tearing pain, pulse/BP differential, neuro deficit | CT angiography/TEE | Rupture; anticoagulation can be catastrophic | | Pulmonary embolism | Pleuritic pain, dyspnea, tachycardia, VTE risk | CT pulmonary angiography or V/Q | Obstructive shock | | Pericarditis | Pleuritic/positional pain, diffuse ST elevation/PR depression | ECG, echo | Tamponade if effusion | | Myocarditis | Viral prodrome, variable ECG, troponin, noncoronary pattern | CMR, echo, selective biopsy | Ventricular arrhythmia/shock | | Tension pneumothorax | Sudden dyspnea, unilateral absent breath sounds, shock | Clinical diagnosis | Immediate death without decompression | | Esophageal rupture | Severe pain after vomiting, systemic toxicity | CT/esophagram | Mediastinitis/sepsis | | GI/musculoskeletal pain | Reproducible or meal-related features may occur | Diagnosis of exclusion in high-risk cases | Risk is missed ACS | ★ **Exam pearl:** Do not give antithrombotics reflexively to undifferentiated tearing chest pain before considering dissection. --- ## STEMI and acute coronary occlusion ### Primary PCI is preferred when timely Primary PCI is the preferred reperfusion strategy when it can be performed within an appropriate system delay. ESC guidance recommends primary PCI when achievable within **120 minutes from STEMI diagnosis**; if timely PCI cannot be achieved and symptom onset is within 12 hours with no contraindication, fibrinolysis is indicated, followed by immediate transfer to a PCI-capable center.[3,5] #### STEMI network principles - Activate the cath lab early. - EMS should preferentially transport to a PCI-capable center when system targets can be met. - Do not wait for troponin when the clinical/ECG diagnosis is clear. - After fibrinolysis, transfer to PCI capability even if symptoms improve. - Rescue PCI is required for failed fibrinolysis or ongoing instability/ischemia. #### Cardiogenic shock Prompt revascularization remains a **Class 1** principle in ACS-related cardiogenic shock.[1,2] Shock management requires a multidisciplinary approach: airway/ventilation when necessary, invasive hemodynamic assessment in selected cases, vasopressor/inotrope support, and mechanical circulatory support only in carefully selected patients because benefit and complications vary by device and phenotype. --- ## NSTE-ACS: risk-stratified invasive management NSTE-ACS includes NSTEMI and unstable angina. An invasive strategy is recommended for ACS, but timing depends on risk.[3] #### Very high-risk features: immediate invasive evaluation Examples include: - Hemodynamic instability/cardiogenic shock - Recurrent or refractory chest pain despite medical treatment - Life-threatening arrhythmia or cardiac arrest attributed to ischemia - Mechanical complication - Acute heart failure clearly driven by ongoing ischemia - Recurrent dynamic ST-segment changes, particularly intermittent ST elevation #### High-risk features Features supporting early/inpatient invasive care include confirmed NSTEMI, significant dynamic ST/T changes, and high clinical risk (e.g., elevated GRACE risk). ESC guidance states an early invasive strategy (<24 h) should be considered in high-risk NSTE-ACS.[3] #### GRACE risk score The GRACE score estimates mortality using age, heart rate, systolic BP, creatinine, Killip class, cardiac arrest, ST deviation, and biomarkers. It is useful for prognosis and invasive-timing decisions, but it does not replace clinical judgment. --- ## Acute pharmacotherapy ### STANDARD OF CARE #### Aspirin The 2025 ACC/AHA guideline dosing table recommends:[1] - **Loading:** **162–325 mg orally**, non-enteric coated; chew when possible for faster effect. - **Maintenance:** **75–100 mg orally daily**. Aspirin is generally continued long term unless contraindicated or a specific antithrombotic strategy modifies it. #### P2Y12 inhibitors For patients undergoing PCI, **ticagrelor or prasugrel is preferred over clopidogrel** when not contraindicated.[1,2] | Agent | Loading | Maintenance | Key cautions | |---|---:|---:|---| | Ticagrelor | 180 mg PO | 90 mg PO twice daily | Dyspnea, bleeding; keep aspirin maintenance ≤100 mg/day | | Prasugrel | 60 mg PO | 10 mg daily if ≥60 kg and <75 y; 5 mg daily if <60 kg or age ≥75 y with caution | **Contraindicated with prior stroke/TIA**; higher bleeding risk | | Clopidogrel | 300 or 600 mg PO without fibrinolysis | 75 mg daily | Variable response; used when potent agents unsuitable | | Clopidogrel with fibrinolysis | 300 mg if age ≤75 y; 75 mg initial dose if >75 y | 75 mg daily | Standard P2Y12 option with fibrinolysis | #### DAPT duration For ACS patients **without high bleeding risk**, aspirin plus an oral P2Y12 inhibitor for **at least 12 months** is the default.[1,2] Bleeding-reduction strategies include: - PPI in patients at GI bleeding risk - In selected patients tolerating ticagrelor-based DAPT after PCI, transition to ticagrelor monotherapy ≥1 month after PCI - If chronic oral anticoagulation is required, discontinue aspirin 1–4 weeks after PCI and continue a P2Y12 inhibitor (preferably clopidogrel) with anticoagulation, individualized to ischemic and bleeding risk.[2] #### Anticoagulation Parenteral anticoagulation is part of acute ACS management, selected according to strategy and renal function (e.g., UFH, enoxaparin, or bivalirudin in appropriate settings). Dosing should follow the local PCI/fibrinolysis protocol because the required dose depends on whether the patient is proceeding to PCI, has already received anticoagulant, renal function, and activated clotting time targets. #### Nitrates For ischemic discomfort or hypertensive pulmonary congestion, sublingual nitroglycerin is commonly used if hemodynamically appropriate. The 2025 guideline cautions against nitrates when: - SBP <90 mmHg or >30 mmHg below baseline - Suspected RV infarction - Recent PDE5 inhibitor exposure: approximately **12 h after avanafil, 24 h after sildenafil/vardenafil, 48 h after tadalafil**.[1] Nitrates improve symptoms; they are **not a substitute for reperfusion** and have not been shown to reduce mortality in modern ACS care. #### Analgesia Opioids are reserved for persistent severe pain despite other anti-ischemic therapy. The 2025 guideline notes morphine **2–4 mg IV**, repeat every 5–15 minutes if needed, with careful monitoring; opioids can delay absorption/effect of oral P2Y12 inhibitors.[1] #### Oxygen Do **not** use routine oxygen solely because ACS is suspected when oxygenation is adequate. Give supplemental oxygen for hypoxemia or respiratory distress and titrate according to the patient's condition and local protocol. #### Beta-blocker In ACS without contraindications, the 2025 guideline recommends **early oral beta-blocker initiation within 24 hours** to reduce reinfarction and ventricular arrhythmias.[1] Delay/avoid in cardiogenic shock, decompensated acute HF, severe bradycardia, high-grade AV block without pacing, or other contraindications. #### High-intensity statin High-intensity statin therapy is recommended for all ACS patients unless contraindicated.[2] Common high-intensity regimens include: - **Atorvastatin 40–80 mg daily** - **Rosuvastatin 20–40 mg daily** The 2025 guideline recommends adding a nonstatin lipid-lowering agent when LDL-C remains **≥70 mg/dL (≥1.8 mmol/L)** on maximally tolerated statin; adding a nonstatin is also reasonable at **55–69 mg/dL** in selected patients.[2] #### ACE inhibitor / ARB and mineralocorticoid receptor antagonist ACEi/ARB is indicated particularly in higher-risk ACS patients (e.g., LVEF ≤40%, hypertension, diabetes, or anterior STEMI). An MRA is indicated for LVEF ≤40% with HF symptoms and/or diabetes when renal function and potassium permit.[1] --- ## PCI and revascularization ### Access and imaging The 2025 guideline recommends **radial access over femoral access** for PCI in ACS to reduce bleeding, vascular complications, and death.[1,2] **Intravascular imaging-guided PCI** is now a **Class 1, Level A** recommendation in the 2025 U.S. guideline.[2] ### Complete revascularization For appropriate STEMI and NSTE-ACS patients with multivessel disease, a strategy of complete revascularization is recommended/strongly favored, with timing and method determined by anatomy, comorbidities, shock status, renal function, lesion complexity, and surgical candidacy.[1,2] ⚠ **Shock exception:** Immediate multivessel PCI in cardiogenic shock is not automatically beneficial; culprit-vessel revascularization remains the immediate priority in many cases, with staged treatment of nonculprit disease according to anatomy and stability. --- ## Complications ### Electrical - Ventricular tachycardia/fibrillation - Accelerated idioventricular rhythm after reperfusion - Sinus bradycardia - AV block, especially inferior MI - Atrial fibrillation Treat unstable arrhythmias according to ACLS while correcting ischemia, hypoxia, potassium, magnesium, and acid-base abnormalities. ### Mechanical — think days after MI, sudden collapse or new murmur | Complication | Typical clue | Hemodynamics / echo | Action | |---|---|---|---| | Papillary muscle rupture → acute MR | Sudden pulmonary edema, shock, new systolic murmur | Severe eccentric MR | Emergency surgery; stabilize with afterload reduction/mechanical support when appropriate | | Ventricular septal rupture | New harsh holosystolic murmur, shock | Left-to-right shunt | Urgent surgical/interventional consultation | | Free-wall rupture | Sudden PEA, tamponade | Pericardial blood/effusion | Emergency surgical management | | LV aneurysm/pseudoaneurysm | Persistent ST changes, HF/embolism | Structural abnormality on echo/CT/CMR | Specialist management; pseudoaneurysm has rupture risk | ### Pump failure - Acute LV failure/pulmonary edema - RV infarction with preload sensitivity - Cardiogenic shock #### RV infarction pearl Suspect with inferior MI, hypotension, elevated JVP, and clear lungs. Obtain right-sided leads. Avoid aggressive nitrates/diuresis if preload dependent; give cautious fluid only if clinically appropriate and reassess frequently. --- ## Special populations ### Older adults and frailty Do not withhold evidence-based ACS care based solely on age. Balance invasive benefit against frailty, cognition, bleeding risk, kidney disease, goals of care, and functional status. ### Chronic kidney disease - hs-cTn may be chronically elevated; rely on dynamic change and clinical context. - Adjust renally cleared drugs. - Minimize contrast burden while avoiding harmful delays in indicated revascularization. ### Patients requiring oral anticoagulation Triple therapy markedly increases bleeding. The 2025 guideline favors early aspirin discontinuation (1–4 weeks after PCI) with continuation of oral anticoagulation plus a P2Y12 inhibitor, usually clopidogrel, when long-term anticoagulation is required.[2] ### Prior stroke/TIA **Prasugrel is contraindicated.** Choose another P2Y12 inhibitor when indicated. ### Pregnancy ACS in pregnancy is uncommon and more likely to involve mechanisms such as spontaneous coronary artery dissection. Management requires a pregnancy-heart team; maternal stabilization and indicated reperfusion take priority, while medication and radiation choices are individualized. --- ## Secondary prevention after ACS ### Before discharge - Smoking cessation treatment - Blood pressure optimization - Diabetes management - High-intensity statin ± nonstatin therapy - Antiplatelet plan documented with duration and bleeding strategy - Echocardiographic assessment of LVEF when appropriate - Cardiac rehabilitation referral - Exercise, weight, diet, and adherence counseling - Review driving/work restrictions per jurisdiction The 2025 guideline recommends a fasting lipid panel **4–8 weeks** after starting or adjusting lipid-lowering therapy and recommends referral to cardiac rehabilitation before discharge.[2] #### Cardiac rehabilitation Cardiac rehabilitation reduces recurrent events, improves functional status and quality of life, and is a Class 1 component of contemporary ACS secondary prevention.[2] --- ## Current guideline changes and areas of nuance ### 2025 ACC/AHA/ACEP/NAEMSP/SCAI — major practical updates **STANDARD OF CARE** - DAPT remains foundational. - Ticagrelor/prasugrel preferred over clopidogrel for PCI when appropriate. - Default DAPT ~12 months when bleeding risk is not high. - Radial PCI access favored. - Intravascular imaging-guided PCI elevated to Class 1. - Complete revascularization emphasized. - High-intensity statin for all ACS. - More aggressive nonstatin lipid-lowering thresholds. - Cardiac rehab referral before discharge.[1,2] ### 2023 ESC vs 2025 U.S. guideline Both support rapid hs-cTn pathways, invasive management for high-risk ACS, potent antiplatelet therapy, radial access, and complete revascularization in appropriate patients. Important practical differences may arise in preferred P2Y12 timing, exact invasive-timing categories, local fibrinolysis systems, and antithrombotic de-escalation strategies. Follow the locally adopted guideline and cath-lab protocol. ### EMERGING EVIDENCE - Individualized antiplatelet de-escalation and monotherapy strategies continue to evolve. - Mechanical circulatory support for selected AMI cardiogenic shock remains an area of active patient-selection research. - Physiology- and imaging-guided complete revascularization strategies continue to be refined. ### EXPERIMENTAL / INVESTIGATIONAL No investigational therapy should replace timely reperfusion, guideline antithrombotic treatment, and secondary prevention outside a trial or specialist protocol. --- ## Acute management checklist ### Suspected ACS - [ ] ABCs; identify shock, pulmonary edema, arrhythmia, cardiac arrest - [ ] Cardiac monitor + defibrillator availability - [ ] IV access - [ ] 12-lead ECG promptly; repeat if nondiagnostic - [ ] Right/posterior leads if indicated - [ ] hs-cTn serial algorithm - [ ] CBC, electrolytes, creatinine, glucose; coagulation studies when relevant - [ ] Aspirin 162–325 mg chewed unless contraindicated - [ ] Determine STEMI/occlusion vs NSTE-ACS pathway - [ ] P2Y12 inhibitor based on strategy and bleeding risk - [ ] Parenteral anticoagulation based on strategy - [ ] Nitrate only if appropriate; check BP/RV infarct/PDE5 exposure - [ ] Oxygen only if indicated - [ ] High-intensity statin - [ ] Early beta-blocker if stable and no contraindication - [ ] Echocardiography for LV function/complications as indicated - [ ] Document DAPT duration and bleeding mitigation - [ ] Cardiac rehab + secondary prevention plan --- ## Diagnostic / management algorithm ```text Acute chest discomfort / dyspnea / ischemic equivalent ↓ ABCs + monitor + IV + 12-lead ECG + hs-cTn ↓ Persistent ST elevation / occlusion pattern with compatible syndrome? ├── YES → STEMI reperfusion pathway │ ├─ Primary PCI achievable within system target → PCI │ └─ PCI not achievable within ~120 min, onset ≤12 h, │ no contraindication → fibrinolysis + transfer to PCI center │ └── NO → NSTE-ACS pathway ↓ Serial hs-cTn + repeat ECG + risk assessment ↓ Very high risk / instability? → Immediate invasive strategy High risk? → Early/inpatient invasive strategy Low risk / ACS ruled out? → Evaluate alternative diagnosis / safe disposition At all stages: Aspirin + strategy-appropriate P2Y12 + anticoagulation + high-intensity statin Treat shock/arrhythmia/HF immediately; reassess continuously ``` --- ## Common pitfalls | Pitfall | Why it is dangerous | Better approach | |---|---|---| | Waiting for troponin before activating clear STEMI | Delays reperfusion | Treat ECG + clinical syndrome as time-critical | | Treating every troponin elevation as type 1 NSTEMI | Causes diagnostic anchoring/bleeding risk | Distinguish injury, type 1 MI, type 2 MI, myocarditis, PE, etc. | | One normal ECG ends the workup | ACS can be dynamic | Repeat ECG during symptoms and use posterior/right leads when indicated | | Routine oxygen in normoxemia | No benefit; potential harm | Give for hypoxemia/respiratory distress | | Nitrates in RV infarction or after PDE5 inhibitor | Severe hypotension | Check hemodynamics and medication history | | Prasugrel in prior stroke/TIA | Major bleeding risk | Use alternative P2Y12 agent | | Ignoring bleeding risk when planning DAPT | Preventable hemorrhage | Use PPI, shortened/modified strategies when appropriate | | Discharge without rehab/lipid plan | Misses high-value prevention | Document secondary prevention before discharge | --- ## Exam-focused review ### Foundation / Step 1 Know plaque rupture/erosion, platelet activation, thrombin/fibrin, subendocardial vulnerability, transmural progression, and the physiologic consequences of reduced coronary blood flow. ### Step 2 CK Priority questions usually ask: **What must happen next?** - STEMI ECG → reperfusion, not stress testing. - Ongoing ischemia with instability → invasive management. - Troponin rise/fall + ischemic evidence without ST elevation → NSTEMI. - Inferior MI + hypotension + clear lungs → consider RV infarction; obtain right-sided leads and avoid nitrates. - New murmur + shock days after MI → mechanical complication. ### Step 3 / Resident Add strategy details: reperfusion timing, fibrinolysis contraindications, antithrombotic selection, bleeding mitigation, shock phenotype, mechanical complications, secondary prevention. ### MRCP / ABIM / boards Expect nuance around: - Type 1 vs type 2 MI - Dynamic hs-cTn interpretation - GRACE risk - Antiplatelet contraindications - DAPT duration in bleeding risk / anticoagulation - Post-MI LV dysfunction therapy - Mechanical complications --- ## Original MCQs #### 1. A 61-year-old man has 90 minutes of crushing chest pain. ECG shows 3 mm ST elevation in V2–V5. Initial hs-cTn is within the reference range. What is the best next step? A. Repeat troponin in 3 hours before treatment B. Exercise stress testing C. Activate immediate reperfusion/primary PCI pathway D. CT coronary angiography first **Answer: C.** Early troponin can be normal. A diagnostic STEMI pattern with an appropriate syndrome requires immediate reperfusion; biomarkers must not delay treatment. #### 2. A patient with inferior STEMI becomes hypotensive after sublingual nitroglycerin. Lungs are clear and JVP is elevated. Best next diagnostic step? A. V4R right-sided ECG lead B. D-dimer C. CT pulmonary angiography D. Stress echocardiography **Answer: A.** The pattern strongly suggests RV infarction with preload dependence. #### 3. Which P2Y12 inhibitor is contraindicated in a patient with prior ischemic stroke? A. Clopidogrel B. Ticagrelor C. Prasugrel D. Cangrelor **Answer: C.** Prasugrel is contraindicated after prior stroke/TIA because of bleeding risk. #### 4. A stable ACS patient undergoes PCI and has no high bleeding risk. What is the contemporary default DAPT duration? A. 48 hours B. 1 month C. 6 weeks D. At least 12 months **Answer: D.** The 2025 ACC/AHA guideline uses at least 12 months as the default in patients without high bleeding risk. #### 5. A patient with NSTEMI has shock, ongoing ischemic pain, and recurrent VT despite initial therapy. What invasive strategy is appropriate? A. Outpatient angiography B. Immediate invasive evaluation C. Stress testing before angiography D. Coronary calcium score **Answer: B.** Very high-risk NSTE-ACS features require immediate invasive care. --- ## References 1. Rao SV, O'Donoghue ML, Ruel M, et al. **2025 ACC/AHA/ACEP/NAEMSP/SCAI Guideline for the Management of Patients With Acute Coronary Syndromes.** *J Am Coll Cardiol.* 2025;85(22):2135–2237. doi: **10.1016/j.jacc.2024.11.009**. https://www.jacc.org/doi/10.1016/j.jacc.2024.11.009 2. American College of Cardiology / American Heart Association. **Top Things to Know: 2025 Guideline for Acute Coronary Syndromes.** Updated February 27, 2025. https://professional.heart.org/en/science-news/2025-guideline-for-the-management-of-patients-with-acute-coronary-syndromes/top-things-to-know 3. Byrne RA, Rossello X, Coughlan JJ, et al. **2023 ESC Guidelines for the management of acute coronary syndromes.** *Eur Heart J.* 2023;44(38):3720–3826. doi: **10.1093/eurheartj/ehad191**. PMID: **37622654**. https://www.escardio.org/guidelines/clinical-practice-guidelines/all-esc-practice-guidelines/acute-coronary-syndromes/ 4. Thygesen K, Alpert JS, Jaffe AS, et al. **Fourth Universal Definition of Myocardial Infarction (2018).** *Circulation.* 2018;138:e618–e651. doi: 10.1161/CIR.0000000000000617. 5. European Society of Cardiology. **Essential Messages from the 2023 ESC Guidelines for the Management of Acute Coronary Syndromes.** 2023. https://www.escardio.org/ 6. Kumbhani DJ, Cibotti-Sun M, Moore MM. **2025 Acute Coronary Syndromes Guideline-at-a-Glance.** *J Am Coll Cardiol.* 2025;85(22):2128–2134. doi: **10.1016/j.jacc.2025.01.018**. 7. Bikdeli B, Ujueta F, Rashedi S, et al. **Antiplatelet and Anticoagulant Therapy in the 2025 ACC/AHA Guideline for Acute Coronary Syndromes: Key Recommendations.** *J Am Coll Cardiol.* 2025. doi: **10.1016/j.jacc.2025.04.002**. --- **Review trigger:** Re-review whenever ACC/AHA or ESC ACS guidance changes, or when major trials alter PCI strategy, cardiogenic-shock support, antiplatelet duration/de-escalation, or lipid-lowering recommendations.1c:T943a,## One-minute summary An **asthma exacerbation** is an acute or subacute worsening of dyspnea, wheeze, cough or chest tightness with a fall in expiratory airflow compared with the patient’s usual state.[1] The attack is caused by variable airflow obstruction from **bronchial smooth-muscle constriction, airway-wall inflammation/edema and mucus**, with dynamic hyperinflation becoming critical in severe disease. The immediate priorities are: 1. **Assess severity while starting treatment.** Do not wait for full history, chest radiography or spirometry. 2. **If anaphylaxis is present, give epinephrine first**, then treat bronchospasm.[1] 3. Give a rapid-acting inhaled bronchodilator. **Salbutamol/albuterol remains the usual acute bronchodilator**; pMDI + spacer is effective for many mild/moderate attacks.[1] 4. In **moderate/severe exacerbations**, give **systemic corticosteroids early**; in adults, GINA 2026 recommends prednisone/prednisolone **40–50 mg/day for 5–7 days**.[1] 5. Add **ipratropium** during the first 1–2 hours for severe acute asthma; this lowers admission risk when combined with SABA.[1] 6. GINA 2026 suggests supplemental oxygen when **SpO₂ <92%**, targeting **92–95%**; avoid unnecessary hyperoxia.[1] 7. Consider **IV magnesium sulfate 2 g over ~20 minutes** in selected severe attacks with poor initial response; it is not routine therapy for every exacerbation.[1] 8. A **normal or rising PaCO₂ in a severely dyspneic patient is ominous**: acute asthma usually causes hypocapnia; normal/high CO₂ suggests fatigue and impending ventilatory failure.[1] 9. Before discharge, ensure **ICS-containing therapy**, inhaler technique, action plan, trigger/risk review and early follow-up. GINA prefers ICS-formoterol-based anti-inflammatory reliever strategies for most adults/adolescents where available.[1,2] ★ **High yield:** A “quiet” or **silent chest** in a distressed patient is not improvement; it can mean critically reduced airflow. --- ## Definition GINA defines an asthma exacerbation as an episode of progressive worsening in shortness of breath, cough, wheeze and/or chest tightness with a progressive decrease in lung function, representing a clinically important departure from the patient’s baseline that requires a change in treatment.[1] Exacerbations may occur: - In a patient with known asthma - As the first presentation of asthma - Despite apparently mild or previously well-controlled symptoms The term **acute severe asthma** describes a high-risk clinical state requiring urgent treatment; **life-threatening/near-fatal asthma** involves features such as altered consciousness, exhaustion, severe hypoxemia, marked airflow limitation or hypercapnia and may require invasive ventilation. --- ## Core pathophysiology ### What narrows the airway? Three mechanisms act together: 1. **Bronchial smooth-muscle contraction** — rapidly reversible with beta₂-agonists. 2. **Airway inflammation and edema** — improved over hours by corticosteroids, not by bronchodilator alone. 3. **Mucus hypersecretion/plugging** — especially important in severe and fatal asthma. ### Dynamic hyperinflation Severe obstruction prolongs expiration. The next inspiration begins before the lungs fully empty, creating **air trapping** and intrinsic PEEP (auto-PEEP). Consequences include: - Increased work of breathing - Respiratory-muscle fatigue - Increased intrathoracic pressure - Reduced venous return and hypotension - Barotrauma/pneumothorax This physiology explains why aggressive mechanical ventilation can be dangerous: the priority is often to permit adequate expiratory time rather than normalize PaCO₂ immediately. ### Gas exchange Early/moderate attacks commonly cause: - V/Q mismatch → hypoxemia - Hyperventilation → **low PaCO₂** As fatigue develops, PaCO₂ normalizes and then rises. In a patient who is still clinically very unwell, that trend should trigger concern for impending respiratory failure.[1] --- ## Triggers and risk factors ### Common exacerbation triggers GINA 2026 lists common triggers including viral respiratory infections, allergen exposure, outdoor air pollution, seasonal changes and poor adherence to inhaled corticosteroid (ICS) treatment.[1] Other triggers include: - Tobacco smoke and vaping exposure - Occupational irritants - Exercise/cold air in susceptible patients - NSAIDs in aspirin/NSAID-exacerbated respiratory disease - Nonselective beta-blockers - Medication nonadherence or incorrect inhaler technique - Thunderstorm asthma in sensitized populations - Pregnancy-related treatment interruption ### Risk factors for severe or fatal exacerbation - Previous intubation/ICU admission for asthma - ED visit or hospitalization in the past year - Recent systemic corticosteroid use - Excess SABA use - Poor/no ICS adherence - Low baseline lung function - Food allergy/anaphylaxis risk - Major psychosocial barriers or poor access to care - Incorrect inhaler technique - Smoking/vaping - Multiple comorbidities GINA emphasizes that dispensing **≥3 SABA canisters/year** is associated with increased exacerbation risk, while very high SABA dispensing is associated with markedly increased mortality risk.[1] --- ## Clinical assessment Treat while assessing. A patient who looks exhausted, confused or cyanotic does not need a prolonged severity checklist before resuscitation. ### Key history - Onset and rate of progression - Trigger: infection, allergen, smoke, medication, exercise - Reliever doses already taken and response - Current controller therapy and adherence - Previous ICU/intubation - Recent steroid courses/admissions - Anaphylaxis symptoms: urticaria, angioedema, hypotension, GI symptoms after exposure - Fever, pleuritic pain or focal infectious symptoms - Pregnancy - Cardiac disease, COPD or other alternative diagnosis ### Examination | Component | Assess | Interpretation | Immediate action | Anticipate deterioration | |---|---|---|---|---| | Appearance | Ability to speak, posture, agitation, drowsiness | Short phrases/words = severe; altered consciousness = life-threatening | Treat immediately; senior/critical care help | Exhaustion, arrest | | Respiratory rate | Trend, not one value | Tachypnea common; slowing with distress can be fatigue | Bronchodilator, O₂ if indicated | Respiratory muscle failure | | Work of breathing | Accessory muscles, retractions, paradoxical movement | Increasing effort = severity; decreasing effort can be fatigue | Repeated bronchodilation | Impending failure | | Air entry | Bilateral intensity, wheeze, silent chest | Quiet chest can mean minimal airflow | Escalate urgently | Need for ventilation | | SpO₂ | Room air if safe; trend | <92% is a GINA 2026 oxygen threshold | Controlled oxygen to 92–95% | Worsening V/Q mismatch | | PEF/FEV₁ | If patient can perform without delaying care | Objective airflow limitation and response | Repeat after treatment | Failure to improve | | HR/BP | Tachycardia, pulsus, hypotension | Severe distress, drug effect, tension PTX, hyperinflation | Monitor; evaluate shock causes | Dynamic hyperinflation | --- ## Severity: practical categories Exact labels vary across guidelines and age groups, but clinical decisions should center on **mild/moderate vs severe vs life-threatening** physiology. ### Mild–moderate pattern - Speaks in phrases/sentences - Alert - Increased work of breathing but not exhausted - SpO₂ often preserved - PEF typically >50% predicted/personal best, often >60% ### Severe pattern - Speaks only words/short phrases - Marked accessory-muscle use - Tachypnea/tachycardia - SpO₂ reduced - PEF ≤50% predicted/personal best is concerning ### Life-threatening pattern Any of the following should prompt immediate escalation: - Drowsiness, confusion, collapse - Exhaustion or poor respiratory effort - Cyanosis - Silent chest/very poor air movement - Severe hypoxemia - Hypotension or arrhythmia - Normal or rising PaCO₂ despite severe distress - Respiratory arrest ★ **Exam pearl:** The loudness of wheeze does **not** reliably correlate with severity. Less wheeze with worsening distress can mean less airflow. --- ## Differential diagnosis | Diagnosis | Clues against uncomplicated asthma | Useful test/action | |---|---|---| | Anaphylaxis | Sudden exposure, urticaria/angioedema, hypotension | **IM epinephrine first** | | COPD exacerbation | Older age, smoking history, chronic fixed obstruction | Prior spirometry, blood gas | | Vocal cord dysfunction / inducible laryngeal obstruction | Inspiratory noise, throat tightness, poor bronchodilator response | Laryngoscopy when stable | | Pneumothorax | Sudden pleuritic pain, unilateral absent breath sounds | POCUS/CXR; emergency decompression if tension physiology | | Pulmonary edema | Crackles, orthopnea, cardiac disease | POCUS, ECG, BNP selectively | | Pulmonary embolism | Sudden dyspnea, risk factors, pleuritic pain | PE pathway | | Pneumonia | Fever, focal crackles, infiltrate | CXR if clinically indicated | | Foreign body | Sudden onset, focal wheeze, choking | Airway evaluation/imaging | | Central airway obstruction | Stridor, fixed monophonic sound | Imaging/bronchoscopy | | Hyperventilation/panic | Paresthesia, normal airflow | Diagnosis of exclusion in acute distress | | Metabolic acidosis | Deep breathing, little wheeze | Blood gas/metabolic work-up | --- ## Investigations ### Peak expiratory flow / spirometry PEF is useful for objective severity and response when the patient can perform it safely. Do **not** delay treatment in severe disease to obtain a number. Repeated values are more informative than one value: - Compare with predicted or personal best - Look for improvement after bronchodilator - Failure to improve should lower the threshold for admission/escalation ### Pulse oximetry Continuous monitoring is appropriate in severe attacks or when oxygen is required. Be aware of potential pulse-oximeter bias and overestimation in some patients with darker skin pigmentation, particularly near clinical thresholds.[1] ### Blood gas GINA 2026 states ABGs are **not routinely required**. Consider them when:[1] - PEF/FEV₁ <50% predicted - Poor response to initial therapy - Clinical deterioration - Suspected ventilatory failure Interpretation: - Low PaCO₂: expected in many acute attacks - Normal PaCO₂ in a very distressed patient: concerning - **PaCO₂ >45 mm Hg (6 kPa)**: respiratory failure signal in this context[1] - PaO₂ <60 mm Hg (8 kPa): significant hypoxemia[1] A VBG may help assess pH/CO₂ trend in selected settings, but arterial sampling is required when exact oxygenation is necessary. ### Chest radiograph Not routine. GINA recommends considering CXR when:[1] - Alternative/complicating cardiopulmonary disease is suspected - The patient is not responding as expected - Pneumothorax may be difficult to diagnose clinically ### Other testing - ECG in older patients, significant tachycardia, chest pain or electrolyte concern - Electrolytes if severe/repeated beta₂-agonist use, diuretics, arrhythmia or critical illness - Viral testing when it changes isolation/antiviral decisions - Pregnancy test when relevant to imaging/medications --- ## Acute management ### First principle: treat concurrently The main acute therapies are administered together rather than sequentially: bronchodilation, oxygen when indicated, systemic anti-inflammatory therapy and escalation planning.[1] --- ### 1. Oxygen #### GINA 2026 update GINA 2026 suggests supplemental oxygen when **SpO₂ <92%** and recommends a target saturation on oxygen of **92–95%** for adults/adolescents/children 6–11 years.[1] In adults with severe exacerbations, controlled low-flow oxygen targeting approximately **93–95%** has better physiologic outcomes than indiscriminate high-concentration oxygen.[1] **Practical point:** If the patient is critically hypoxemic and pulse oximetry is not immediately available, do not withhold oxygen while waiting for a reading.[1] #### Why avoid hyperoxia? Excess oxygen can worsen V/Q relationships and is unnecessary when saturation is already adequate. Titrate rather than automatically using 100% oxygen for every attack. --- ### 2. Rapid bronchodilation #### Salbutamol/albuterol For mild-to-moderate exacerbations, repeated inhaled SABA is highly effective. Common GINA-based adult/adolescent acute dosing is **4–10 puffs (100 micrograms/puff) by pMDI + spacer every 20 minutes for up to 3 doses in the first hour**, adjusted to response.[1] GINA 2026 primary-care flowcharts further stratify dosing, with severe presentations receiving **6–10 puffs by pMDI + spacer or 5 mg by nebulizer**, repeated every 20–30 minutes if needed.[1] #### pMDI + spacer vs nebulizer For many non-life-threatening exacerbations, pMDI + spacer produces similar lung-function improvement to nebulized SABA and is more resource-efficient.[1,8] Nebulization remains appropriate when the patient cannot effectively use a spacer, requires very high/continuous delivery, or is critically ill according to local protocol. #### Adverse effects - Tremor - Tachycardia - Hypokalemia with high cumulative doses - Lactic acidosis with very intensive beta₂-agonist exposure ⚠ **Common trap:** Persistent tachypnea after heavy salbutamol therapy is not always persistent bronchospasm. Consider beta₂-agonist-associated lactate elevation if airflow has improved but tachypnea remains. --- ### 3. Ipratropium bromide Add inhaled **ipratropium** to SABA during the **first 1–2 hours** for severe acute asthma. GINA notes that this combination reduces hospital admission risk compared with SABA alone.[1] Typical adult severe-attack regimens vary by delivery system/local policy, for example: - Ipratropium **0.5 mg nebulized**, often repeated with initial SABA treatments, or - pMDI + spacer dosing according to local protocol. There is generally **no benefit from continuing ipratropium after the initial 1–2 hours** once the acute phase has improved.[1] --- ### 4. Systemic corticosteroids Give systemic corticosteroids early for **moderate or severe exacerbations**, especially when response to initial bronchodilator is incomplete.[1] #### Adults GINA 2026 discharge/acute guidance recommends: - **Prednisone/prednisolone 40–50 mg orally once daily for 5–7 days**.[1] Oral therapy is preferred when the patient can absorb/tolerate medication; IV corticosteroids are not inherently superior if oral delivery is reliable. #### Why early? Corticosteroids reduce airway inflammation, accelerate recovery and reduce relapse risk. Their onset is not immediate, which is why they should be given early rather than “after bronchodilators fail.” #### Taper? A short 5–7-day adult course generally does not require tapering when the patient is not on chronic systemic steroids; chronic steroid exposure requires individualized adrenal-axis planning. --- ### 5. IV magnesium sulfate **Not routine for every attack.** Consider IV magnesium in severe exacerbations with inadequate response to initial intensive treatment, particularly persistent hypoxemia or very low lung function.[1] Typical adult regimen: - **Magnesium sulfate 2 g IV over ~20 minutes once**.[1] Evidence supports reduced hospital admission in selected severe patients; nebulized magnesium has not shown consistent benefit.[1] --- ### 6. Epinephrine when asthma is part of anaphylaxis A major 2026 emphasis is explicit: **if the patient has features of anaphylaxis and asthma, give epinephrine first**.[1] Bronchodilators treat bronchospasm but do not treat the airway edema, vasodilation and cardiovascular collapse of anaphylaxis. Use the standard anaphylaxis pathway; IM epinephrine dosing is weight-based and protocol-specific. --- ### Treatments that are NOT routine #### Antibiotics Do not prescribe antibiotics routinely for an asthma exacerbation. Use them only when there is evidence of a bacterial infection such as pneumonia, bacterial sinus disease requiring treatment, or another defined indication.[1] #### Aminophylline/theophylline Not recommended routinely because it adds toxicity with little additional benefit over modern inhaled bronchodilator therapy.[1] #### Sedatives Avoid sedatives in severe acute asthma unless required for a controlled airway procedure: respiratory depression can precipitate arrest. #### Routine mucolytics Not recommended; airway irritation may worsen cough/bronchospasm. --- ## Reassessment after initial treatment Reassess at approximately **1 hour or earlier** in severe disease.[1] #### Reassess - Symptoms and ability to speak - Mental status - Respiratory rate and work of breathing - SpO₂ and oxygen requirement - Air entry/wheeze - PEF/FEV₁ if feasible - HR/BP - Need for ongoing SABA #### Favorable response - Marked symptom improvement - Normalizing work of breathing - Adequate oxygenation without escalating oxygen - PEF improving toward >60–80% predicted/personal best - Reliever effect persists #### Poor response / deterioration - Persistent inability to speak - Increasing fatigue/drowsiness - Silent chest - Persistent hypoxemia - PEF persistently <50% or falling - Normal/rising PaCO₂ - Hemodynamic instability → Escalate to senior respiratory/critical-care support and prepare for ventilatory support. --- ### Noninvasive ventilation Evidence for NIV in acute asthma is less robust than in COPD exacerbation. A closely monitored trial may be considered in selected cooperative patients in experienced units, but **NIV must not delay intubation** in a deteriorating patient. Avoid NIV in: - Reduced consciousness - Inability to protect airway - Severe agitation/uncooperativeness - Hemodynamic instability - Impending arrest - Copious secretions/vomiting risk --- ### Indications to consider intubation There is no single mandatory numeric threshold. Intubate for clinical failure, including: - Respiratory arrest/peri-arrest - Progressive exhaustion - Declining consciousness - Inability to maintain oxygenation - Progressive hypercapnia/acidosis with clinical deterioration - Severe hemodynamic instability - Failure of maximal medical therapy Call anesthesia/critical care early; severe asthma is a high-risk airway and ventilation problem. --- ### Mechanical ventilation in status asthmaticus #### Key objective Avoid dangerous dynamic hyperinflation. #### Principles - Lower respiratory rate - Modest tidal volume - High inspiratory flow / short inspiratory time - Long expiratory time - Monitor plateau pressure and auto-PEEP - Accept **permissive hypercapnia** when necessary if pH/hemodynamics remain acceptable - Treat bronchospasm aggressively - Deep sedation initially; neuromuscular blockade only when necessary #### Sudden hypotension after intubation Think immediately of: 1. **Dynamic hyperinflation/auto-PEEP** 2. Tension pneumothorax 3. Sedative-induced vasodilation 4. Hypovolemia If severe auto-PEEP is suspected, disconnecting briefly from the ventilator to allow exhalation can be diagnostic/temporizing while definitive ventilator changes are made by experienced clinicians. --- ### Complications #### From the disease - Respiratory failure/arrest - Pneumothorax/pneumomediastinum - Mucus plugging/atelectasis - Hypoxic injury - Cardiac arrest #### From treatment | Therapy | Important adverse effects | |---|---| | High-dose beta₂-agonist | Tremor, tachycardia, hypokalemia, lactate elevation | | Systemic corticosteroid | Hyperglycemia, mood change, infection risk with repeated courses | | Ipratropium | Dry mouth, ocular exposure issues | | Magnesium | Flushing, hypotension; toxicity in major renal impairment with repeated dosing | | Mechanical ventilation | Barotrauma, hypotension, auto-PEEP | --- ## Disposition ### Consider discharge when - Symptoms substantially improved - No life-threatening features - Oxygenation adequate without supplemental oxygen - Lung function has improved substantially (often PEF >60–80% predicted/personal best, integrated with clinical state) - Reliever need is not excessive - Patient can use inhalers correctly - Safe follow-up and medications are available ### Admit when - Severe or incompletely responsive exacerbation - Persistent hypoxemia - PEF remains low or deteriorates - Significant comorbidities or pregnancy with concern - Previous near-fatal asthma plus concerning current course - Social barriers make outpatient treatment unsafe ### ICU / high-dependency care - Life-threatening features - Hypercapnia/acidosis - Need for NIV or invasive ventilation - Hemodynamic instability - Rapid deterioration despite treatment --- ## Discharge management: preventing the next attack An exacerbation is a sentinel event. The goal is not simply to stop wheezing; it is to reduce future severe attacks and preventable death. #### 1. ICS-containing therapy is mandatory GINA 2026 emphasizes ICS-containing treatment for all adults/adolescents with asthma and prefers **ICS-formoterol anti-inflammatory reliever strategies** where available.[1,2] For adults/adolescents after acute care, GINA recommends initiating or optimizing ICS-containing therapy before discharge; **MART (maintenance-and-reliever therapy) with ICS-formoterol** is preferred for many patients because it reduces future exacerbations compared with SABA-reliever regimens.[1] #### 2. Oral steroid course Adults: prednisone/prednisolone **40–50 mg/day for 5–7 days** when indicated.[1] #### 3. Reliever strategy Return the patient to **as-needed**, not scheduled, reliever use. Patients who use ICS-formoterol as reliever should resume it before/on discharge if SABA was temporarily substituted in acute care.[1] #### 4. Action plan Provide/review a written plan explaining: - Daily controller regimen - How to recognize worsening asthma - How to increase reliever/controller according to the plan - When to seek urgent/emergency care #### 5. Technique and adherence Watch the patient use the inhaler. “Do you know how?” is not equivalent to demonstration. #### 6. Follow-up GINA recommends follow-up **within 2–7 days** after discharge for adults/adolescents (earlier for many high-risk patients).[1] Refer for specialist review after: - ICU/intubation - Recurrent exacerbations - ≥1 exacerbation requiring oral corticosteroids/urgent care in the previous 12 months despite treatment - Diagnostic uncertainty - Suspected difficult-to-treat/severe asthma --- ### Why ICS-formoterol changed asthma care Large trials in mild asthma demonstrated that as-needed budesonide-formoterol substantially reduces severe exacerbations compared with SABA-only treatment while using less total ICS than daily maintenance regimens in some populations.[4-7] These data underpin the modern move away from **SABA-only asthma treatment**. The 2024 BTS/NICE/SIGN chronic asthma guideline similarly states that SABA should not be prescribed without concomitant ICS and favors anti-inflammatory reliever approaches in appropriate patients.[3] **Guideline convergence:** GINA and BTS/NICE/SIGN differ in exact algorithms and licensed products, but both reject SABA-only management as an adequate long-term strategy. --- ### Special populations #### Pregnancy Treat exacerbations aggressively: maternal hypoxemia is a greater fetal risk than standard asthma medicines. Continue ICS-containing treatment. Do not undertreat because of pregnancy. #### Children 6–11 years Use age/weight-specific pathways. GINA 2026 uses controlled oxygen targets and age-specific bronchodilator/steroid dosing; avoid simply copying adult doses.[1] #### Children ≤5 years Acute wheeze has a broad differential. GINA 2026 specifies salbutamol dosing by spacer/nebulizer and age-specific corticosteroid doses; pMDI + spacer is preferred when feasible.[1] #### Older adults Consider competing diagnoses: heart failure, ACS, PE, COPD, medication effects. Beta₂-agonist tachycardia and hypokalemia may be more consequential. #### Aspirin/NSAID-exacerbated respiratory disease Avoid culprit COX-1 inhibitors and refer for specialist management; acute bronchospasm is treated conventionally, but prevention requires recognition of the phenotype. --- ### Anticipation of deterioration | Finding | Meaning | Action | |---|---|---| | Increasing SABA need with shorter relief | Uncontrolled obstruction | Reassess severity; systemic steroid/escalation | | Falling wheeze + falling air entry | Less airflow, not necessarily improvement | Urgent senior/critical-care review | | Drowsiness/confusion | Hypoxemia/hypercapnia/exhaustion | Airway/ventilation planning | | Normalizing PaCO₂ while still distressed | Fatigue | Treat as impending respiratory failure | | Hypotension | Auto-PEEP, tension PTX, dehydration, anaphylaxis | Immediate focused evaluation | | Rising lactate after very high SABA dose with improving airflow | Beta₂-agonist effect possible | Reassess bronchospasm before escalating SABA blindly | --- ### Acute management checklist #### Immediate - [ ] Sit patient upright if tolerated - [ ] Rapid ABC assessment - [ ] Identify anaphylaxis → **epinephrine first** - [ ] SpO₂, HR, RR, BP, mental status - [ ] PEF if feasible without delaying treatment - [ ] Inhaled salbutamol/albuterol promptly - [ ] Oxygen if SpO₂ <92%; target 92–95% (GINA 2026) - [ ] Add ipratropium for severe exacerbation - [ ] Systemic corticosteroid early for moderate/severe attack - [ ] Senior/critical-care help for life-threatening features #### At 1 hour or earlier - [ ] Repeat clinical severity assessment - [ ] Repeat PEF/FEV₁ if feasible - [ ] Check oxygen requirement - [ ] Consider blood gas if PEF/FEV₁ <50%, poor response or deterioration - [ ] Consider IV magnesium 2 g for selected severe poor responders - [ ] Consider CXR only if alternative/complication suspected - [ ] Decide discharge vs admission vs ICU #### Before discharge - [ ] ICS-containing controller/reliever plan - [ ] Complete appropriate OCS course - [ ] Demonstrate inhaler technique - [ ] Written asthma action plan - [ ] Trigger/risk review - [ ] Avoid SABA-only long-term management - [ ] Follow-up within 2–7 days --- ### Diagnostic / management algorithm ```text Acute dyspnea/wheeze in patient with possible asthma ↓ ABC + severity + SpO₂ + PEF if feasible ↓ Anaphylaxis features? ├─ Yes → epinephrine FIRST + anaphylaxis pathway + bronchodilator └─ No ↓ Life-threatening features? ├─ Yes → emergency transfer/ICU + intensive bronchodilator │ + ipratropium + systemic steroid + controlled O₂ │ + consider Mg + early airway plan └─ No ↓ SABA by pMDI+spacer (or nebulizer when appropriate) + systemic steroid if moderate/severe + O₂ only if hypoxemic ↓ Reassess ≤1 hour ↓ Good response? ├─ Yes → observe → discharge plan with ICS-containing therapy └─ No → repeat/escalate bronchodilator + ipratropium + blood gas if severe + consider IV Mg + admit / critical-care review ↓ Fatigue, altered consciousness, rising PaCO₂, refractory hypoxemia? → prepare for invasive ventilation with long expiratory time strategy ``` --- ### Common pitfalls | Pitfall | Why dangerous | Better approach | |---|---|---| | Judging severity by wheeze volume | Silent chest may be near-fatal | Assess air entry, effort, mentation, PEF, gas exchange | | Waiting for CXR before bronchodilator/steroid | Delays effective treatment | Treat first; image selectively | | Routine 100% oxygen | Hyperoxia is unnecessary and potentially harmful | Controlled O₂ to 92–95% when SpO₂ <92% | | Repeated SABA without reassessment | Can worsen tachycardia/hypokalemia/lactate and miss fatigue | Reassess airflow and physiology | | Missing anaphylaxis | Bronchodilator does not treat systemic anaphylaxis | Epinephrine first | | Withholding steroids until “very severe” | Steroids take hours to work | Give early in moderate/severe attacks | | Discharging on SABA alone | Does not treat airway inflammation; higher future risk | ICS-containing regimen | | Intubating then ventilating at high rate | Causes dynamic hyperinflation/hypotension | Slow rate, long expiration, permissive hypercapnia | --- ### STANDARD OF CARE vs emerging vs experimental #### STANDARD OF CARE - Rapid severity assessment and repeated reassessment - Inhaled rapid bronchodilator - Controlled oxygen for hypoxemia - Early systemic corticosteroids for moderate/severe exacerbations - Ipratropium in severe acute asthma during first 1–2 hours - Selective IV magnesium in severe poor responders - Early airway/critical-care involvement in life-threatening disease - ICS-containing therapy and action plan at discharge #### EMERGING / RECENTLY EVOLVING PRACTICE - **2026 GINA acute-care oxygen threshold/target revision:** oxygen suggested below 92%, target 92–95%.[1] - Addition of **ICS-formoterol as an alternative reliever treatment for some mild acute presentations** in 2026 GINA flowcharts, while SABA remains the usual bronchodilator in acute care.[1] - Increasing use of anti-inflammatory reliever/MART strategies immediately after an exacerbation to reduce recurrence.[1-7] #### EXPERIMENTAL / SPECIALIST-ONLY - Extracorporeal support for refractory near-fatal asthma - Heliox in selected refractory cases (not routine) - Advanced bronchoscopic mucus-clearance approaches in exceptional cases - Biologic therapy is important for long-term severe asthma prevention but is **not a substitute for standard acute resuscitation** during a life-threatening attack --- ### Guideline differences and jurisdiction notes #### GINA 2026 - International strategy document - Strong emphasis on ICS-containing therapy for all asthma - Prefers Track 1 ICS-formoterol reliever strategy in adults/adolescents where available - 2026 acute oxygen approach: treat when SpO₂ <92%, target 92–95%[1] #### BTS/NICE/SIGN (UK) The 2024 joint chronic-asthma guideline does not itself replace all retained BTS/SIGN acute-attack recommendations, but it explicitly recommends against prescribing SABA without concomitant ICS and supports anti-inflammatory reliever/MART pathways.[3] #### Local formularies Exact inhaler strengths, approved age groups, AIR/MART licensing and nebulized medication doses differ by country. Always reconcile international strategy with local product labeling and emergency protocols. --- ### Exam-focused review #### Step 1 Know: - Reversible bronchoconstriction + inflammation + mucus - V/Q mismatch → hypoxemia - Severe obstruction → air trapping and dynamic hyperinflation - Beta₂ agonism → bronchodilation, tremor, tachycardia, hypokalemia #### Step 2 CK / Step 3 Priorities: - Acute severe asthma → bronchodilator + systemic steroid early - Anaphylaxis with wheeze → **epinephrine**, not “more albuterol only” - Tension pneumothorax → decompress - Drowsy patient with rising CO₂ → impending respiratory failure #### MRCP / ABIM / boards Remember: - Normal PaCO₂ can be abnormal in severe acute asthma - CXR and ABG are selective, not routine - IV magnesium is for selected severe poor responders - Aminophylline is not routine - Discharge without ICS-containing therapy is poor modern asthma care --- ### Original MCQs #### Question 1 A 24-year-old woman with asthma is speaking in single words, using accessory muscles and has SpO₂ 89% on room air. Which initial plan is best? A. Chest radiograph before treatment B. Oral antibiotic + observe C. Inhaled rapid bronchodilator, controlled oxygen, systemic corticosteroid, add ipratropium and reassess urgently D. Sedative to reduce respiratory drive E. SABA only, discharge when wheeze decreases **Answer: C.** **Explanation:** This is severe acute asthma. Treatment should begin immediately and concurrently. Imaging is selective and must not delay bronchodilation/anti-inflammatory therapy.[1] #### Question 2 A severely dyspneic patient initially had PaCO₂ 28 mm Hg. Two hours later she remains exhausted and PaCO₂ is 42 mm Hg. What is the best interpretation? A. Clear improvement because CO₂ normalized B. Impending ventilatory failure C. Metabolic alkalosis D. SABA toxicity only E. Normal finding requiring no escalation **Answer: B.** **Explanation:** Acute asthma usually causes hypocapnia. A normalizing/rising CO₂ in a patient who remains severely distressed indicates loss of ventilatory reserve and fatigue.[1] #### Question 3 A man presents with wheeze, lip swelling, generalized urticaria and hypotension minutes after eating peanuts. What should be given first? A. Inhaled salbutamol B. IV magnesium C. IM epinephrine D. Prednisolone E. Ipratropium **Answer: C.** **Explanation:** This is anaphylaxis with bronchospasm. GINA 2026 explicitly emphasizes epinephrine first; bronchodilators are adjuncts.[1] #### Question 4 Which is the strongest indication for a chest radiograph in an asthma exacerbation? A. Every patient with wheeze B. Mild attack responding to one bronchodilator dose C. Poor response with sudden unilateral chest pain and markedly reduced breath sounds D. Known asthma and normal exam after treatment E. Need to confirm bronchospasm **Answer: C.** **Explanation:** Routine CXR is not recommended, but suspected pneumothorax or another complicating process is a clear indication.[1] #### Question 5 An adult improves after ED treatment for a moderate exacerbation. Which discharge strategy best reduces future severe attacks? A. SABA alone B. Stop all inhalers after steroid course C. Ensure ICS-containing therapy, preferably an ICS-formoterol-based strategy where appropriate, plus action plan and early follow-up D. Daily antibiotics E. Maintenance oral prednisone indefinitely **Answer: C.** **Explanation:** Modern GINA strategy centers on anti-inflammatory reliever/controller treatment rather than SABA-only care; follow-up and self-management are essential.[1-7] --- ### What changed recently? #### GINA 2026 acute asthma GINA’s 2026 report added/revised acute asthma flowcharts and made several clinically important changes:[1] - If asthma occurs with anaphylaxis, **epinephrine is explicitly prioritized first**. - Supplemental oxygen is suggested when **SpO₂ <92%**, with target **92–95%**. - For mild exacerbations, **ICS-formoterol was added as an alternative reliever option** in appropriate adults/adolescents/children 6–11 depending on formulation/setting. - Discharge strategy increasingly emphasizes **MART/anti-inflammatory reliever treatment** rather than returning patients to SABA dependence. These are meaningful changes from older teaching that routinely targeted higher oxygen saturations and reflexively used SABA as the only acute reliever option in all mild presentations. --- ### Landmark and influential research - **SYGMA 1 (2018):** as-needed budesonide-formoterol reduced severe exacerbation risk versus SABA-only therapy in mild asthma, establishing the anti-inflammatory reliever concept.[4] - **SYGMA 2 (2018):** as-needed budesonide-formoterol was noninferior to maintenance budesonide for severe exacerbations with lower corticosteroid exposure, though symptom-control differences remained.[5] - **Novel START (2019):** in a pragmatic population, as-needed budesonide-formoterol reduced exacerbations versus albuterol-only therapy.[6] - **PRACTICAL (2019):** as-needed budesonide-formoterol reduced severe exacerbations compared with maintenance budesonide plus SABA in a pragmatic open-label trial.[7] - Spacer-vs-nebulizer evidence supports pMDI + spacer as an effective route for many non-life-threatening acute attacks.[8] --- ### References 1. Global Initiative for Asthma (GINA). *Global Strategy for Asthma Management and Prevention: 2026 Update*. 2026. https://ginasthma.org/2026-gina-strategy-report/ 2. Global Initiative for Asthma (GINA). *2026 Summary Guide for Asthma Management and Prevention*. 2026. https://ginasthma.org/2026-gina-summary-guide/ 3. British Thoracic Society, National Institute for Health and Care Excellence, Scottish Intercollegiate Guidelines Network. *Asthma: diagnosis, monitoring and chronic asthma management (BTS, NICE, SIGN)*. NICE NG245. Published 27 November 2024; minor update November 2025. https://www.nice.org.uk/guidance/ng245 4. O'Byrne PM, FitzGerald JM, Bateman ED, et al. Inhaled Combined Budesonide-Formoterol as Needed in Mild Asthma (SYGMA 1). *N Engl J Med*. 2018;378:1865-1876. doi:10.1056/NEJMoa1715274. 5. Bateman ED, Reddel HK, O'Byrne PM, et al. As-Needed Budesonide-Formoterol versus Maintenance Budesonide in Mild Asthma (SYGMA 2). *N Engl J Med*. 2018;378:1877-1887. doi:10.1056/NEJMoa1715275. 6. Beasley R, Holliday M, Reddel HK, et al. Controlled Trial of Budesonide-Formoterol as Needed for Mild Asthma (Novel START). *N Engl J Med*. 2019;380:2020-2030. doi:10.1056/NEJMoa1901963. 7. Hardy J, Baggott C, Fingleton J, et al. Budesonide-formoterol reliever therapy versus maintenance budesonide plus terbutaline reliever therapy in adults with mild to moderate asthma (PRACTICAL). *Lancet*. 2019;394:919-928. doi:10.1016/S0140-6736(19)31948-8. 8. Cates CJ, Welsh EJ, Rowe BH. Holding chambers (spacers) versus nebulisers for beta-agonist treatment of acute asthma. *Cochrane Database Syst Rev*. 2013;(9):CD000052. doi:10.1002/14651858.CD000052.pub3. --- ### Related topics to build next - Chronic asthma: diagnosis and long-term management - Difficult-to-treat and severe asthma - Anaphylaxis - COPD exacerbation - Respiratory failure and mechanical ventilation - Pneumothorax - Inhaler pharmacology and device technique1d:T8da2,## One-minute summary The **ABCDE approach** is a structured method for the immediate assessment and treatment of a deteriorating or critically ill patient: **A**irway, **B**reathing, **C**irculation, **D**isability, **E**xposure. The central rule is **treat life-threatening abnormalities as soon as they are found, then reassess from A**.[1,2] ABCDE is designed for **physiologic stabilization before diagnostic completeness**. It is useful in emergency departments, wards, critical care, perioperative settings, clinics, and prehospital care. The 2025 Resuscitation Council UK (RCUK) First Aid Guidelines explicitly endorse a structured ABCDE assessment for people who appear ill, injured, or in shock.[2] **Do not continue a routine ABCDE survey in a patient who is unresponsive and not breathing normally:** activate the cardiac-arrest pathway and start CPR according to current resuscitation guidance.[1,3] ### Core sequence ```text Safety → responsiveness → call for help ↓ A Airway: patent and protected? ↓ B Breathing: oxygenation and ventilation adequate? ↓ C Circulation: perfusion adequate? bleeding? shock? ↓ D Disability: consciousness, pupils, glucose, focal deficit? ↓ E Exposure: hidden clues, temperature, environment? ↓ REASSESS A → B → C → D → E after every important intervention ``` ★ **HIGH YIELD:** ABCDE is a **treat-as-you-find** framework, not “finish the examination, then begin treatment.” --- ## General principles 1. **Treat the greatest immediate threat first.** 2. **Call for help early** if the patient is critically ill or deterioration is likely.[1] 3. **Use the team in parallel:** monitoring, IV access, blood sampling, medication preparation, airway equipment, documentation, and escalation can occur simultaneously.[1] 4. **Reassess after interventions** because the response to treatment determines the next step.[1] 5. **Do not delay lifesaving treatment for a definitive diagnosis.** 6. **Trend physiology**, not isolated numbers: respiratory rate, work of breathing, SpO₂, pulse, blood pressure, mental status, perfusion, urine output, lactate, and response to therapy. 7. **Escalate early** when the patient may require airway expertise, critical care, surgery, interventional radiology, cardiology, neurology, obstetrics, pediatrics, toxicology, or transfer. The ABCDE concept is broadly applicable because airway obstruction, respiratory failure, shock, and neurologic compromise can kill more quickly than many definitive diagnoses can be established.[4] --- ## Clinical applications Use ABCDE for any patient who is **potentially unstable**, including: - sudden deterioration on a ward - severe dyspnea or hypoxemia - shock or suspected sepsis - major bleeding - altered mental status - anaphylaxis - poisoning/overdose - major trauma - peri-arrest states - acute neurologic deterioration - postoperative deterioration - obstetric or pediatric emergencies, with population-specific modifications ### When ABCDE is not the primary pathway If the patient is **unresponsive and not breathing normally**, manage as possible cardiac arrest rather than spending time completing a conventional ABCDE survey.[1,3] ⚠ **COMMON TRAP:** Agonal gasps are abnormal breathing and may occur during cardiac arrest. --- ## First 30 seconds — before A A rapid global impression can reveal critical illness before detailed examination. | Step | What to do | Why it matters | |---|---|---| | Safety | Confirm scene/personal safety; use appropriate PPE | Protects patient and team | | Responsiveness | Speak to the patient; assess response | A coherent answer suggests current airway patency, ventilation, cerebral perfusion, and neurologic function | | Help | Call emergency/resuscitation/senior help early | Complex stabilization is a team task | | Monitoring | Apply pulse oximetry, ECG monitoring, and noninvasive BP early when feasible | Establishes trends and detects deterioration | | Access | Obtain IV access and blood samples when indicated | Enables treatment and diagnostics | | Arrest check | If unresponsive and not breathing normally, activate cardiac-arrest response | CPR/defibrillation take priority | RCUK emphasizes early monitoring, IV access, teamwork, structured communication, and repeated reassessment in critically ill patients.[1] --- ## A — Airway ### Goal Determine whether the airway is **patent, maintainable, and protectable**, and correct life-threatening obstruction immediately. ### Why airway comes first Complete airway obstruction rapidly prevents oxygen delivery. Even partial obstruction can worsen suddenly because of edema, blood, vomitus, secretions, foreign material, trauma, reduced consciousness, or progressive upper-airway pathology.[1,4] ### Airway assessment and immediate management | Component | Assessment | Concerning findings | Immediate action | Anticipate deterioration when… | |---|---|---|---|---| | Speech | Ask patient to speak | Hoarse voice, weak voice, inability to speak | Call for help; prepare airway support | voice is changing, swelling progressing | | Sounds | Listen without a stethoscope first | Stridor, snoring, gurgling, silence | Airway maneuvers, suction, adjuncts, expert help | stridor, swelling, reduced consciousness | | Mouth/oropharynx | Inspect if safe | Blood, vomit, secretions, foreign body, edema | Suction/remove visible obstruction as appropriate | bleeding or secretions continue | | Consciousness | AVPU/GCS trend | Reduced airway protection | Position, adjunct, ventilation; consider definitive airway | GCS/alertness falling | | Neck/face | Trauma, swelling, burns, hematoma | Distortion, rapidly progressive edema | Early anesthetic/ENT/critical-care involvement | expanding neck hematoma, angioedema, inhalation injury | | Air movement | Look/listen/feel | Minimal or absent airflow | Immediate airway opening + ventilation support | fatigue or obstruction worsening | ### Immediate airway interventions Depending on cause, setting, and expertise: - call for expert airway help early - open the airway with appropriate maneuvers - suction blood, vomit, or secretions - remove visible foreign material when appropriate - insert an oropharyngeal or nasopharyngeal airway when indicated - provide bag-mask ventilation if ventilation is inadequate - use a supraglottic airway as a rescue/bridge when appropriate - proceed to tracheal intubation when a definitive airway is required and expertise is available - prepare for emergency front-of-neck access if oxygenation/ventilation cannot be achieved by conventional means RCUK notes that simple airway-opening measures and adjuncts are sufficient in many cases, while tracheal intubation may be required when these fail.[1] #### Causes of threatened airway - reduced consciousness - foreign-body obstruction - blood/vomit/secretions - anaphylaxis/angioedema - inhalational or facial burns - neck hematoma or penetrating injury - upper-airway infection or mass - facial/maxillofacial trauma - seizures - intoxication/sedation #### Trauma note If cervical-spine injury is possible, minimize unnecessary neck movement, but **do not allow spinal precautions to prevent airway opening or oxygenation**. ⚠ **RED FLAGS** - stridor - rapidly progressive facial/tongue/neck swelling - inability to handle secretions - falling level of consciousness - silent airway with respiratory effort - severe facial/neck trauma - smoke inhalation with evolving airway edema ★ **EXAM PEARL:** A patient who can speak normally has a patent airway **at that moment**; it does not guarantee continued patency. --- ## B — Breathing ### Goal Determine whether oxygenation and ventilation are adequate, recognize immediately life-threatening thoracic/respiratory disorders, and support breathing while treating the cause. ### Breathing assessment | Component | Assess | Key abnormal patterns | Immediate implications | |---|---|---|---| | General appearance | agitation, confusion, fatigue, cyanosis | agitation may be early hypoxemia; somnolence may signal hypercapnia/fatigue | escalate monitoring and support | | Respiratory rate | rate and trend | tachypnea, bradypnea, apnea | severe abnormalities can precede arrest | | Speech | full sentences vs words only | short phrases suggest marked respiratory distress | urgent support/treatment | | Work of breathing | accessory muscles, recession, paradoxical movement | increased effort or exhaustion | impending respiratory failure | | Chest movement | symmetry and depth | unilateral reduction | pneumothorax, hemothorax, effusion, obstruction | | Auscultation | bilateral air entry, wheeze, crackles | silent chest, unilateral absent sounds, diffuse wheeze, crackles | targeted emergency therapy | | Percussion | hyperresonance/dullness when useful | hyperresonance vs dullness | pneumothorax vs fluid/consolidation | | SpO₂ | saturation and trend | hypoxemia | oxygen and cause-specific therapy | | CO₂ assessment | capnography/blood gas when indicated | hypercapnia or hypocapnia | assesses ventilation and severity | ### Immediately dangerous breathing problems Think especially about: - tension pneumothorax - severe asthma/bronchospasm - pulmonary edema - massive hemothorax - severe pneumonia - pulmonary embolism - respiratory muscle failure - opioid/sedative respiratory depression - airway obstruction causing secondary ventilatory failure #### Oxygen RCUK’s ABCDE guidance recommends high-concentration oxygen initially for critically ill patients, followed by titration once reliable monitoring is available. For acute respiratory failure, typical targets are **94–98% for most patients** and **88–92% for patients at risk of hypercapnic respiratory failure**, unless an individualized target is documented.[1] #### Ventilatory support If spontaneous ventilation is inadequate: 1. open/secure the airway 2. assist ventilation, commonly beginning with bag-mask ventilation 3. add airway adjuncts when needed 4. escalate to noninvasive or invasive ventilation when appropriate 5. treat the underlying reversible cause #### Bedside tests and monitoring Depending on severity: - continuous pulse oximetry - respiratory-rate monitoring - arterial or venous blood gas - capnography/capnometry - portable chest radiography - lung/pleural point-of-care ultrasound ⚠ **COMMON TRAP:** A normal SpO₂ does **not** prove adequate ventilation. A patient can retain dangerous amounts of CO₂ while oxygen saturation appears acceptable, especially while receiving supplemental oxygen. ✓ **NEXT BEST STEP:** In obvious severe respiratory failure, support oxygenation/ventilation **before** sending the patient for nonessential imaging. --- ## C — Circulation ### Goal Recognize shock, hemorrhage, dysrhythmia, or other circulatory failure and restore adequate tissue perfusion while treating the cause. ### Circulation assessment | Component | What to assess | Concerning findings | What they suggest | |---|---|---|---| | Mental status | confusion, agitation, drowsiness | deterioration | cerebral hypoperfusion, hypoxemia, metabolic cause | | Skin | color, temperature, mottling, diaphoresis | cool/mottled or markedly flushed | shock pattern varies by etiology | | Pulse | rate, rhythm, volume, symmetry | tachycardia, bradycardia, weak pulse, asymmetry | shock, dysrhythmia, vascular emergency | | BP | repeated/trended measurements | hypotension or severe hypertension | shock or hypertensive emergency | | Capillary refill | trend in context | prolonged refill | possible poor peripheral perfusion | | JVP/volume clues | neck veins, edema, mucosa | low vs high filling signs | helps distinguish hypovolemia from obstructive/cardiogenic states | | Bleeding survey | external, GI, thoracic, abdominal, pelvic, retroperitoneal | ongoing blood loss | hemorrhagic shock | | Urine output | trend when catheterization indicated | oliguria | possible renal hypoperfusion | ★ **HIGH YIELD:** **Normal blood pressure does not exclude shock.** Compensatory vasoconstriction may preserve blood pressure despite inadequate tissue perfusion.[1] ### Initial circulatory actions - control obvious external hemorrhage immediately - establish IV access; use IO access when necessary and appropriate - obtain blood samples while access is established - apply continuous cardiac monitoring when indicated - obtain a 12-lead ECG for suspected ischemia/dysrhythmia - use blood gas/lactate and other tests according to context - consider point-of-care ultrasound to help identify shock physiology - begin cause-specific resuscitation without waiting for diagnostic perfection ### Shock framework | Shock type | Typical clues | Immediate priorities | |---|---|---| | Hypovolemic/hemorrhagic | bleeding, low filling signs, tachycardia, cool skin | hemorrhage control, blood products when indicated, cautious crystalloid where appropriate | | Distributive | sepsis/anaphylaxis; may have warm peripheries early | cause-specific treatment, fluids when appropriate, vasopressors when indicated | | Cardiogenic | pulmonary edema, ischemia, high JVP, cool peripheries | cautious fluids, reperfusion/arrhythmia management, vasoactive support, specialist care | | Obstructive | tamponade, tension pneumothorax, massive PE | immediate relief/treatment of obstruction | #### Fluids are not one-size-fits-all Use the suspected cause, comorbidities, dynamic response, and disease-specific guidance to determine fluid strategy. Reassess after each intervention. Excess fluid can worsen cardiogenic shock, pulmonary edema, and some other states. #### Major hemorrhage Priorities may include: - hemorrhage control - major hemorrhage/massive transfusion protocol activation - balanced blood-component or whole-blood strategies according to local protocol - correction of coagulopathy and hypothermia - urgent surgery/interventional radiology - anticoagulant reversal when indicated #### Obstructive emergencies - **tension pneumothorax:** emergency decompression followed by definitive pleural drainage according to trauma/emergency protocol - **cardiac tamponade:** urgent drainage in the appropriate clinical context - **high-risk pulmonary embolism with hemodynamic collapse:** reperfusion strategy according to PE guidance #### Distributive emergencies - **anaphylaxis:** intramuscular epinephrine/adrenaline is first-line - **sepsis/septic shock:** rapid antimicrobials, source control, hemodynamic support according to current sepsis guidance - **adrenal crisis:** glucocorticoid replacement and supportive therapy ### Useful rapid investigations - ECG - CBC - electrolytes/renal function - glucose - blood gas and lactate - coagulation tests - type and screen/crossmatch - troponin when ACS suspected - cultures when infection suspected and they do not delay treatment - POCUS when expertise is available ⚠ **COMMON TRAP:** Treating “hypotension” with repeated fluid boluses without considering cardiogenic or obstructive shock. --- ## D — Disability ### Goal Rapidly assess neurologic function and correct immediately reversible causes of impaired consciousness. ### Disability assessment | Component | What to check | Why | |---|---|---| | Level of consciousness | AVPU/ACVPU and/or GCS | detects deterioration and airway-protection risk | | Pupils | size, symmetry, reactivity | clues to structural neurologic disease or toxins | | Glucose | bedside capillary/POC glucose | hypoglycemia is rapidly reversible | | Focal deficits | face, speech, limbs, gaze as appropriate | stroke/intracranial pathology | | Seizure activity | ongoing or recent | requires urgent treatment and airway consideration | | Toxidrome clues | pupils, skin, secretions, respiratory pattern | directs antidote/supportive therapy | #### First principle: revisit ABC causes Before attributing altered consciousness to a primary brain disorder, reconsider: - hypoxemia - hypercapnia - shock/cerebral hypoperfusion - hypoglycemia - sedatives/opioids/toxins Then consider stroke, intracranial hemorrhage, seizures, meningitis/encephalitis, traumatic brain injury, raised intracranial pressure, electrolyte disorders, and other causes. #### Immediate reversible conditions - hypoglycemia → glucose according to local protocol - opioid toxicity with respiratory depression → airway/ventilation support and naloxone when indicated - ongoing convulsive status epilepticus → benzodiazepine-based emergency seizure treatment followed by protocolized escalation - suspected bacterial meningitis → prompt empiric antimicrobial therapy once appropriate initial steps are taken; do not allow nonessential imaging to create dangerous delay - suspected raised ICP/herniation → urgent neurocritical/neurosurgical pathway and neuroprotective measures ⚠ **COMMON TRAP:** Sending an unstable obtunded patient straight to CT before correcting hypoxia, hypotension, hypoglycemia, or active seizures. #### Airway and consciousness Reduced consciousness may compromise airway protection, but **a single GCS threshold should not be used mechanically without clinical context**. Consider trajectory, airway reflexes, ventilation, oxygenation, aspiration risk, anticipated course, and available expertise. --- ## E — Exposure / Environment ### Goal Perform a sufficiently complete examination to identify hidden pathology while preserving dignity and preventing environmental harm. ### Exposure assessment Look for: - trauma, burns, wounds, bruising - rashes, petechiae, purpura - cellulitis, gangrene, infected surgical sites - bleeding or occult sources of blood loss - edema - abdominal distention or peritonism - limb ischemia - track marks, transdermal patches, toxic exposures - devices, drains, catheters, stomas - bites/stings or retained foreign material - pregnancy-related clues when relevant Measure temperature and manage hypothermia or hyperthermia appropriately. #### Environmental control - replace wet or contaminated clothing - remove ongoing allergen/toxin exposure where safe - begin rewarming or cooling as indicated - re-cover the patient after examination - preserve privacy and dignity ★ **HIGH YIELD:** Exposure means **look thoroughly, then protect the patient from heat loss and environmental harm**. --- ## Reassessment — the essential sixth step ABCDE is **cyclical**, not linear. After every meaningful intervention, ask: - **A:** Is the airway now patent and likely to remain so? - **B:** Has oxygenation, ventilation, respiratory rate, or work of breathing improved? - **C:** Has perfusion improved? What happened to pulse, BP, capillary refill, mental status, urine output, lactate? - **D:** Has consciousness or glucose improved? Any new focal deficit? - **E:** Has a hidden cause or environmental problem been identified? RCUK specifically emphasizes reassessing the patient and evaluating the effect of treatment.[1] ⚠ **RED FLAG:** Any deterioration during later assessment or secondary survey should trigger an immediate return to **A**. --- ## Anticipation of deterioration A high-quality ABCDE assessment does not only ask “what is wrong now?” It asks **“what may fail next?”** | Domain | High-risk features | Prepare for | |---|---|---| | Airway | angioedema, inhalation injury, expanding neck hematoma, worsening consciousness | advanced airway equipment, expert airway team, rescue airway plan | | Breathing | escalating O₂ need, exhaustion, silent chest, rising CO₂ | assisted ventilation, NIV/intubation, critical care | | Circulation | ongoing bleeding, rising lactate, worsening perfusion, escalating vasopressor need | major hemorrhage response, invasive monitoring, definitive source control | | Disability | declining GCS, recurrent seizures, focal deterioration, signs of herniation | airway protection, urgent imaging when stable enough, neurocritical/neurosurgical care | | Exposure | hypothermia, toxin contamination, spreading infection, concealed hemorrhage | rewarming/decontamination/source control | ★ **BOARD-LEVEL POINT:** Deterioration often becomes obvious first as a **trend**—rising respiratory rate, increasing oxygen requirement, narrowing pulse pressure, altered mentation, or increasing support needs—before a single dramatic threshold is crossed. --- ## Crisis resource management and team performance The ABCDE method works best when the team functions deliberately. ### Key principles - establish a clear team leader - allocate tasks explicitly - use **closed-loop communication** - announce important findings and changes - avoid fixation on a single diagnosis - anticipate next steps and prepare equipment early - call additional expertise before crisis becomes irreversible - use structured handover, such as **SBAR** #### Closed-loop communication A task is assigned to a named person, repeated back, completed, and completion is announced. This reduces ambiguity during emergencies. #### Cognitive forcing question At intervals, the team leader should ask: > “What is the immediate threat now, what have we treated, and what could deteriorate next?” --- ## Adjuncts to the ABCDE assessment Adjuncts depend on presentation and should **support rather than delay stabilization**. ### Monitoring - continuous ECG monitoring - pulse oximetry - frequent or continuous blood pressure measurement - capnography where indicated - temperature - urine output in selected critically ill patients ### Access - peripheral IV access - IO access if vascular access is urgently needed and IV access cannot be established promptly - arterial/central access when clinically indicated after initial stabilization ### Point-of-care and laboratory testing Possible tests include: - bedside glucose - ABG/VBG - lactate - CBC - electrolytes and renal function - liver chemistry - coagulation studies - troponin - pregnancy testing when relevant - type and screen/crossmatch - cultures and microbiology when infection is suspected - targeted toxicology testing rather than indiscriminate screening ### Imaging For unstable patients, prioritize tests that can be performed **at the bedside or without delaying treatment**, including: - point-of-care ultrasound - portable chest radiograph - focused trauma ultrasound where appropriate CT and other advanced imaging generally follow once the patient can be transported safely, unless an immediately necessary diagnostic pathway requires otherwise. --- ## Secondary survey and definitive phase Once immediate life threats are controlled: 1. obtain a fuller history 2. perform a head-to-toe examination appropriate to the presentation 3. review medications, allergies, comorbidities, events, and collateral history 4. complete diagnostic testing 5. establish a working diagnosis and differential 6. arrange definitive therapy 7. determine level of care: ward, high-dependency/step-down, ICU, operating room, catheterization lab, stroke unit, transfer, etc. 8. perform structured handover #### SAMPLE history when useful - **S**igns/symptoms - **A**llergies - **M**edications - **P**ast medical history/pregnancy - **L**ast oral intake - **E**vents leading to illness/injury If the patient deteriorates during the secondary survey, **stop and repeat ABCDE immediately**. --- ## Acute management checklist ### Airway - assess ability to speak and airway sounds - inspect for obstruction, blood, vomit, edema, trauma - suction/open airway as needed - use adjuncts when appropriate - call for difficult-airway expertise early - prepare definitive/rescue airway if deterioration is likely ### Breathing - respiratory rate, SpO₂, work of breathing - chest symmetry and bilateral air entry - oxygen to an appropriate target - assist ventilation if inadequate - treat tension pneumothorax, severe bronchospasm, pulmonary edema, or other immediate cause - use blood gas/capnography/POCUS when indicated ### Circulation - pulse, BP, perfusion, capillary refill - search for bleeding - obtain IV/IO access - ECG and blood sampling - cause-specific shock management - reassess after fluids/blood/vasoactive therapy ### Disability - AVPU/ACVPU or GCS - pupils - bedside glucose - focal neurologic signs - seizure/toxin assessment - correct reversible causes promptly ### Exposure - whole-body inspection as appropriate - temperature - remove wet/contaminated clothing or ongoing triggers - prevent heat loss ### Then - reassess A–E - obtain fuller history and examination - pursue definitive diagnosis and treatment - arrange disposition and handover --- ## Diagnostic and management algorithm ```text Acutely unwell / deteriorating patient ↓ Safety + responsiveness + summon help ↓ Unresponsive AND not breathing normally? ├── YES → Cardiac-arrest pathway / CPR / AED-defibrillation as indicated └── NO ↓ A — Airway patent and maintainable? ├── NO → Airway opening/suction/adjunct/ventilation/expert airway help │ ↓ reassess A └── YES ↓ B — Oxygenation and ventilation adequate? ├── NO → Oxygen/ventilatory support + treat immediate respiratory cause │ ↓ reassess A-B └── YES ↓ C — Perfusion adequate? bleeding/shock/arrhythmia? ├── NO → Hemorrhage control + access + cause-specific resuscitation │ ↓ reassess A-C └── YES ↓ D — Neurologic impairment / hypoglycemia / seizure / toxin? ├── YES → Correct reversible cause + urgent neurologic/toxicologic pathway └── NO ↓ E — Expose, inspect, temperature/environment control ↓ REPEAT ABCDE ↓ Secondary survey + diagnostics + definitive care + disposition ``` --- ## Common pitfalls | Pitfall | Why dangerous | Better practice | |---|---|---| | Long history before stabilization | delays treatment of immediate threats | ABCDE first, fuller history later | | Completing all of A–E before treating | allows reversible deterioration to progress | treat abnormalities as found | | Focusing on diagnosis rather than physiology | may delay oxygenation/perfusion support | stabilize first, diagnose in parallel | | Normal BP = no shock | compensated shock may preserve BP | assess global perfusion and trends | | Normal SpO₂ = adequate ventilation | hypercapnia may be missed | assess respiratory effort and CO₂ when indicated | | Repeated fluid boluses for every hypotensive patient | may worsen cardiogenic/obstructive states | use cause-specific resuscitation | | Missing bedside glucose | overlooks a reversible cause of altered consciousness | check early in D | | Failure to expose | hidden rash, bleeding, trauma, devices, infection missed | perform adequate whole-body inspection | | Failure to re-cover | promotes hypothermia and loss of dignity | exposure + environmental control | | No reassessment | treatment may fail or patient may deteriorate | repeat ABCDE after interventions | | Poor task allocation | delays parallel care | leadership + closed-loop communication | --- ## Special populations ### Trauma Trauma systems may use **ABCDE** or **XABCDE**, placing catastrophic external hemorrhage control before airway when exsanguinating bleeding is immediately apparent. Follow the trauma protocol in use locally. Cervical-spine precautions modify airway technique but must not prevent oxygenation or ventilation. ### Pediatrics The same physiologic priorities apply, but airway anatomy, normal vital-sign ranges, fluid therapy, drug dosing, shock patterns, and deterioration differ substantially by age. Use current pediatric life-support guidance. ### Pregnancy Apply ABCDE with pregnancy physiology in mind. Maternal oxygenation and perfusion are the primary determinants of fetal oxygen delivery. Advanced pregnancy may require positioning strategies to reduce aortocaval compression during resuscitative care. ### Older adults Older patients may have limited physiologic reserve, atypical presentations, beta-blocker use that blunts tachycardia, renal vulnerability, and high risk from both under- and over-resuscitation. ### Toxicology Airway, ventilation, ECG, glucose, temperature, and toxidrome recognition are especially important. Use targeted antidotes when indicated, but supportive ABC care remains fundamental. --- ## Evidence and current guidance ### ESTABLISHED STANDARD OF CARE - Structured ABCDE assessment for acutely unwell patients is longstanding and internationally used.[1,4] - Treat life-threatening abnormalities as they are identified and reassess frequently.[1] - If the patient is unresponsive and not breathing normally, switch immediately to cardiac-arrest management.[1,3] - Early teamwork, monitoring, vascular access, and structured communication improve the efficiency of emergency assessment.[1] ### NEW / UPDATED GUIDANCE The **2025 RCUK First Aid Guidelines** introduced first aid as a dedicated guideline chapter and explicitly recommend structured ABCDE assessment for a person who appears ill, injured, or in shock.[2] The **2025 AHA Adult Basic Life Support Guidelines** supersede the prior full 2020 BLS set and update adult cardiac-arrest, respiratory-arrest, and foreign-body-airway-obstruction guidance.[3] ### EMERGING EVIDENCE ABCDE itself is primarily a structured clinical framework rather than a single therapeutic intervention. Evidence evaluating its effect on outcomes is less extensive than evidence for individual treatments embedded within the framework. Its enduring value is in prioritization, communication, repeated reassessment, and early correction of physiologic threats.[4] --- ## Exam-focused review ### USMLE Step 1 — mechanisms Know the physiology behind: - airway obstruction → alveolar hypoventilation/hypoxemia - respiratory failure → hypoxemia and/or hypercapnia - shock → reduced tissue perfusion → anaerobic metabolism/lactate - sympathetic compensation → tachycardia and vasoconstriction - hypoglycemia → neuroglycopenia ### USMLE Step 2 CK — next best step Common pattern: > **Unstable patient + possible diagnosis → stabilize first.** Examples: - airway compromise before CT - severe respiratory failure before definitive imaging - active major hemorrhage before prolonged diagnostic workup - hypoglycemia correction before broad neurologic testing ### Step 3 / Resident Expect decisions about: - when to escalate to airway/critical care - shock subtype and resuscitation strategy - reassessment after interventions - disposition and transfer - complications of treatment ### MRCP / ABIM / Board level High-yield nuances: - normal BP does not exclude shock - oxygenation and ventilation are distinct - a single GCS number does not automatically determine airway management - fluid strategy depends on shock phenotype and comorbidity - trends and response to treatment often matter more than single measurements - cognitive errors such as fixation and premature closure are important in deteriorating patients --- ## Original MCQs ### Question 1 — next best step A 67-year-old patient becomes drowsy and tachypneic on the ward. SpO₂ is 82% on room air, BP is 118/70 mmHg, and the patient can answer only one-word questions. What is the best immediate approach? A. Obtain CT pulmonary angiography B. Complete a full neurologic examination C. Begin ABCDE stabilization with immediate respiratory support D. Wait for arterial blood gas results before treatment E. Obtain a detailed medication history **Answer: C.** **Explanation:** The patient is unstable with severe hypoxemia and respiratory distress. Stabilization of airway/breathing takes priority over definitive diagnosis. Imaging and detailed history follow once immediate physiologic threats are addressed.[1] **Tested concept:** next-best-step prioritization **Difficulty:** Step 2 CK / MRCP --- ### Question 2 — shock A trauma patient is tachycardic, cool, clammy, and confused. BP is 112/74 mmHg. Which statement is most accurate? A. Shock is excluded because systolic BP is >100 mmHg B. The patient may have compensated shock despite normal BP C. Lactate must be elevated before shock can be diagnosed D. Hypotension is required before hemorrhage control E. CT should precede resuscitation **Answer: B.** **Explanation:** Compensatory vasoconstriction can preserve blood pressure despite reduced perfusion. Clinical perfusion and trends matter.[1] **Tested concept:** compensated shock **Difficulty:** Step 2 CK / Step 3 --- ### Question 3 — ventilation A patient with COPD is somnolent on supplemental oxygen with SpO₂ 95%. Which statement is most important? A. Normal SpO₂ excludes respiratory failure B. Pulse oximetry directly measures PaCO₂ C. Hypercapnia may still be present despite acceptable SpO₂ D. Oxygen should always be stopped immediately E. Respiratory rate is not useful **Answer: C.** **Explanation:** Pulse oximetry assesses oxygen saturation, not ventilation or CO₂ clearance. Blood gas and clinical assessment may reveal hypercapnic respiratory failure. **Tested concept:** oxygenation vs ventilation **Difficulty:** MRCP / ABIM --- ### Question 4 — disability An obtunded patient arrives after an unwitnessed collapse. Which bedside test belongs early in the disability assessment because it identifies a rapidly reversible cause? A. EEG B. Lumbar puncture C. Blood glucose D. MRI brain E. Carotid Doppler **Answer: C.** **Explanation:** Hypoglycemia is a rapidly reversible cause of altered mental status and should be checked promptly during D.[1] **Tested concept:** reversible causes of altered consciousness **Difficulty:** Step 2 CK --- ### Question 5 — reassessment After airway suction and bag-mask ventilation, the patient's oxygen saturation improves. What is the best next action? A. Proceed directly to discharge planning B. Continue to C without checking the airway again C. Reassess from A, then continue through ABCDE D. Wait 30 minutes before reassessment E. Perform only a neurologic examination **Answer: C.** **Explanation:** ABCDE is iterative. After an important intervention, reassess the effect of treatment and return to the beginning of the sequence.[1] **Tested concept:** reassessment **Difficulty:** Foundation / Step 2 CK --- ## Cross-links for the library Future linked articles should include: - Airway management - Oxygen therapy - Respiratory failure - Shock - Sepsis and septic shock - Anaphylaxis - Altered mental status and coma - Trauma primary and secondary survey - Cardiac arrest and CPR - Point-of-care ultrasound in shock --- ## References 1. **Resuscitation Council UK.** *The ABCDE Approach.* Updated July 2024. Official clinical guidance. https://www.resus.org.uk/library/abcde-approach 2. **Resuscitation Council UK.** *First Aid Guidelines — 2025 Resuscitation Guidelines.* Published October 27, 2025. Based on European Resuscitation Council Guidelines 2025 First Aid. https://www.resus.org.uk/professional-library/2025-resuscitation-guidelines/first-aid-guidelines 3. **Kleinman ME, Buick JE, Huber N, et al.** Part 7: Adult Basic Life Support: 2025 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. *Circulation.* 2025;152(Suppl 2):S448-S478. doi:10.1161/CIR.0000000000001369. 4. **Thim T, Krarup NHV, Grove EL, Rohde CV, Løfgren B.** Initial assessment and treatment with the Airway, Breathing, Circulation, Disability, Exposure (ABCDE) approach. *International Journal of General Medicine.* 2012;5:117-121. doi:10.2147/IJGM.S28478. PMID:22319249. --- ### Editorial note This article is an original synthesis for Dr Note Library. It is designed to provide layered learning from foundational physiology through clinical stabilization and board-level reasoning. It should be updated whenever major resuscitation, airway, oxygen, trauma, or critical-care guidance changes.7:["$","$L17",null,{"article":{"id":"medical-0009","title":"Acute Pulmonary Embolism","slug":"acute-pulmonary-embolism","description":"Acute pulmonary embolism (PE) is obstruction of the pulmonary arterial circulation by thrombus, usually arising from deep veins of the legs or pelvis. The immediate threat is acute right-ventricular (RV) pressure over…","aliases":[],"category":"Pulmonology","tags":["Pulmonology","Vascular Medicine","Cardiology","Emergency Medicine"],"updatedAt":"2026-09-08","body":"$18","headings":[{"id":"one-minute-summary","text":"One-minute summary","level":2},{"id":"1-definition-and-core-concepts","text":"1. 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