Aspiration pneumonitis and pneumonia

Also known as Aspiration pneumonitis (Mendelson syndrome) · Aspiration pneumonia · Chemical pneumonitis · Acid aspiration injury

Aspiration of gastric contents causes two distinct entities: aspiration PNEUMONITIS (chemical injury from acidic gastric contents — sterile inflammation, no initial infection) vs aspiration PNEUMONIA (bacterial infection from aspirated oropharyngeal flora). Pneumonitis (Mendelson syndrome): acute onset after witnessed aspiration of acidic (pH < 2.5) gastric contents, CXR infiltrates in dependent lobes within hours, STERILE initially. Pneumonia: develops over 24-48h with fever, purulent sputum, progressive infiltrates. Management: airway protection, suction, supportive ventilation if needed. Do NOT routinely give antibiotics for pneumonitis (chemical injury — sterile) — they do not prevent secondary infection and drive resistance. Give antibiotics ONLY if infection declares itself: persistent fever 48h, purulent sputum, progressive infiltrates, rising inflammatory markers, or high baseline risk (institutionalised, recent antibiotics, sepsis, immunocompromise). Corticosteroids confer no benefit. Lung-protective ventilation for the ~10% that progress to ARDS.

medium24 referencesUpdated 26 July 202621 min readVerification in progress

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Aspiration pneumonITIS is a sterile chemical burn from acidic gastric contents (pH < 2.5) — Mendelson syndrome. Aspiration pneumONIA is a bacterial infection of aspirated oropharyngeal flora. The split decides whether you reach for antibiotics or not. Do NOT give antibiotics for pneumonitis (sterile initially; they do not prevent secondary infection and drive resistance). Add antibiotics ONLY when infection declares itself — fever beyond 48 h, purulent sputum, progressive infiltrates, rising inflammatory markers — or when baseline bacterial risk is high (institutionalised, recent antibiotics, sepsis, immunocompromise). Steroids and saline lavage are NOT recommended. Affected segments are gravity-driven — posterior upper lobe plus apical lower lobe when supine, basal lower lobe when upright, right lung more often than left. About 10% of massive aspirations progress to ARDS, and that is the killer, not the infection.^[1]

Meet the patient

A 45-year-old with poorly controlled epilepsy is brought in after a generalised tonic-clonic seizure at home. He vomited during the post-ictal phase; his Glasgow score on arrival is 10. He is tachypnoeic at 30 with widespread inspiratory crackles, SpO₂ 90 per cent on room air. A chest X-ray taken within two hours shows bilateral perihilar infiltrates. His temperature is 37.0 °C, WCC 11.2, CRP 12, procalcitonin 0.06.^[1]

The registrar asks whether to start piperacillin-tazobactam and methylprednisolone. He is asking the wrong question. The right question is what is the injuring agent, and how long ago? — because the answer determines every drug decision downstream.^[1]

References24Show

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