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Lithium Anaesthetic Interactions — FRCA Final MCQ

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ModerateGeneral AnaesthesiaLithium Anaesthetic InteractionsFRCA Final

A 45-year-old woman (ASA II) on long-term lithium therapy for bipolar disorder requires anaesthesia for elective cholecystectomy. What is the most important perioperative concern with lithium?

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Correct answer: D — Lithium prolongs the action of both depolarising and non-depolarising neuromuscular blocking agents

Lithium is a clinically significant drug in anaesthesia because it prolongs the action of both suxamethonium AND non-depolarising neuromuscular blocking agents. The mechanism involves lithium's effect on sodium channels and acetylcholine synthesis/release at the neuromuscular junction. Additionally: lithium has a narrow therapeutic index (0.6-1.2 mmol/L), is renally excreted (affected by dehydration, NSAIDs, ACE inhibitors), and perioperative fluid shifts/renal impairment can cause toxicity. Lithium should be continued perioperatively with level monitoring, adequate hydration, and avoidance of NSAIDs.

Reference: BNF – 2025 – Lithium interactions; RCOA – 2023 – Drug interactions in anaesthesia