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Nitrous oxide pneumothorax — FRCA Primary MCQ

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HardPharmacologyNitrous oxide pneumothoraxFRCA Primary

A ventilated trauma patient with pneumothorax deteriorates after an inhaled adjunct expands a closed gas space. Which drug is most likely responsible?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Nitrous oxide

Nitrous oxide diffuses into closed gas spaces faster than nitrogen leaves, expanding them. Hydrocortisone is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Atracurium is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Calcium chloride is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. Four-factor prothrombin complex concentrate with vitamin K is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. In Primary FRCA pharmacology, link the clinical effect to the receptor, distribution or elimination mechanism rather than memorising isolated facts.

Reference: Peck, Hill & Williams Pharmacology for Anaesthesia and Intensive Care; BNF; Primary FRCA textbooks