Acute Respiratory Distress Syndrome

Key points

• ARDS: increased alveolar-capillary permeability causing non-cardiogenic pulmonary oedema, refractory hypoxaemia and stiff lungs.
• Causes: sepsis and pneumonia (commonest), aspiration, massive transfusion (TRALI), smoke/toxic inhalation, acute pancreatitis, trauma/fat embolism.
• Berlin definition: acute onset within 1 week of a known insult; bilateral infiltrates not fully explained by effusion/collapse; respiratory failure not fully explained by cardiac failure or fluid overload; hypoxaemia graded by PaO2/FiO2 (mild 200-300, moderate 100-200, severe under 100, with PEEP 5+).
• Management: treat the underlying cause; lung-protective ventilation - low tidal volume (about 6 mL/kg ideal body weight) with limited plateau pressure, accepting permissive hypercapnia.
• For moderate-severe ARDS: prone positioning improves outcomes; use a conservative fluid strategy; consider neuromuscular blockade and ECMO in refractory cases.