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Carbon monoxide poisoning — RCPSC EM MCQ

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EasyToxicologyCarbon monoxide poisoningRCPSC EM

A 44-year-old man is found in a garage in winter with headache, vomiting and confusion. His wife has similar symptoms. SpO2 reads 100% on pulse oximetry, ABG PaO2 is normal, lactate is 4.9 mmol/L, and carboxyhaemoglobin is 28%. What is the most likely diagnosis?

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Correct answer: E — Carbon monoxide poisoning

Normal pulse oximetry can be misleading in carbon monoxide poisoning. Shared exposure, neurologic symptoms and elevated carboxyhaemoglobin confirm the diagnosis.

Reference: Poison centre toxicology guidance; Goldfrank-style ED toxicology principles