## Most Common Cause of ARDS **Key Point:** Sepsis is the most common cause of ARDS, accounting for approximately 40–50% of all ARDS cases in ICU populations. ### Epidemiology of ARDS Causes | Cause | Frequency | Clinical Context | | --- | --- | --- | | **Sepsis** | 40–50% | Pneumonia, intra-abdominal infection, urinary tract infection | | Aspiration | 10–15% | Altered consciousness, anesthesia, dysphagia | | Trauma | 10–15% | Blunt/penetrating injury, fat embolism | | Acute pancreatitis | 5–10% | Alcohol, gallstones, post-ERCP | | Transfusion-related acute lung injury (TRALI) | 5% | Blood product administration | | Drug toxicity | <5% | Chemotherapy, antibiotics | ### Why Sepsis Dominates **High-Yield:** Sepsis causes ARDS through: 1. Systemic inflammatory response (TNF-α, IL-1, IL-6 release) 2. Increased pulmonary capillary permeability 3. Neutrophil infiltration and activation 4. Surfactant dysfunction 5. Alveolar-capillary barrier breakdown **Clinical Pearl:** In the ICU setting, sepsis-induced ARDS has a mortality rate of 30–40%, higher than non-sepsis ARDS. The patient in this vignette has community-acquired pneumonia progressing to sepsis-induced ARDS — the classic presentation. ### Diagnostic Confirmation ARDS diagnosis requires: - Acute onset (within 1 week of insult) - Bilateral opacities on imaging (not explained by effusion, atelectasis, or nodules) - Respiratory failure not explained by cardiac failure or fluid overload - PaO₂/FiO₂ ≤ 300 mmHg (mild), ≤ 200 mmHg (moderate), ≤ 100 mmHg (severe) [cite:Berlin ARDS Definition 2012] **Mnemonic:** **ARDS Sepsis Dominance** — **A**cute **R**espiratory **D**istress from **S**epsis is the leading cause in ICU populations.
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