A family sleeping in a closed room with an unvented coal chulha is found comatose the next morning, with cherry-pink skin and pulse oximetry reading 98 percent despite severe metabolic acidosis. The most appropriate immediate management is:

• A Immediate endotracheal intubation with room air ventilation
• B 100 percent oxygen by tight-fitting mask; consider hyperbaric oxygen if available ✓
• C Intravenous sodium bicarbonate correction before any oxygen therapy
• D Methylene blue infusion

Explanation

This is carbon monoxide poisoning: CO binds haemoglobin with over 200 times the affinity of oxygen, forming carboxyhemoglobin that does not transport oxygen yet reads normally on conventional pulse oximetry, explaining the spurious 98 percent saturation. Treatment is 100 percent oxygen to accelerate dissociation, with hyperbaric oxygen reserved for severe cases. Methylene blue treats methaemoglobinaemia, the classic distractor here.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.