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Ketamine mechanism — FRCA Primary MCQ

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EasyPharmacologyKetamine mechanismFRCA Primary

A shocked trauma patient receives an induction drug and becomes hypertensive with preserved respiratory effort for a short period. What is the most likely explanation?

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Correct answer: E — It antagonises NMDA receptors

Ketamine produces dissociative anaesthesia and analgesia through NMDA receptor antagonism with sympathomimetic effects. It inhibits adrenal 11-beta hydroxylase is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. It chelates unfractionated heparin is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. It is hydrolysed by nonspecific esterases is less appropriate because it would fit a different clinical clue or a separate anaesthetic problem. It undergoes Hofmann elimination 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