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Suxamethonium hyperkalaemia after denervation — FRCA Primary MCQ

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HardPharmacologySuxamethonium hyperkalaemia after denervationFRCA Primary

A 57-year-old patient under anaesthesia develops hyperkalaemia after suxamethonium. He has a spinal cord injury from 3 months earlier. What is the most likely mechanism?

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

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Correct answer: E — Reduced potassium release because of muscle wasting

Denervation and prolonged immobility cause upregulation of extrajunctional acetylcholine receptors, so suxamethonium can produce dangerous potassium efflux. Plasma cholinesterase inhibition would prolong paralysis but is not the mechanism of hyperkalaemia. Autonomic dysreflexia may occur after spinal injury but does not explain suxamethonium potassium release. The teaching point is to avoid suxamethonium in established denervation states.

Reference: RCoA Primary FRCA Syllabus 2026; Peck, Hill & Williams Pharmacology for Anaesthesia