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Insulin potassium shift — FRCA Primary MCQ

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ModeratePhysiologyInsulin potassium shiftFRCA Primary

A patient with renal failure has potassium 6.8 mmol/L and ECG changes before urgent surgery. Insulin with glucose is prescribed. What is the principal immediate effect?

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Correct answer: A — Shift of potassium into cells

Insulin stimulates cellular uptake of potassium, rapidly lowering extracellular potassium concentration. It does not rely on renal excretion, which is impaired in this patient. It does not chelate potassium or significantly alter intestinal absorption acutely. Calcium stabilises the myocardium, while insulin-glucose buys time by redistributing potassium.

Reference: Ganong Review of Medical Physiology; Emergency anaesthesia texts