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Hypokalaemia — RACP Adult Medicine MCQ

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EasyNephrologyHypokalaemiaRACP Adult Medicine

A 62-year-old woman on a thiazide diuretic presents with muscle cramps, weakness, and ECG showing prominent U waves and flattened T waves. Na⁺ 139, K⁺ 2.6, Cl⁻ 94, HCO₃⁻ 32 mmol/L, Mg²⁺ 0.6 mmol/L. What is the most likely electrolyte abnormality causing symptoms?

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Correct answer: C — Hypokalaemia

Prominent U waves and flattened T waves are ECG hallmarks of hypokalaemia. Thiazide diuretics cause hypokalaemia via renal potassium wasting. The metabolic alkalosis (elevated bicarbonate) is a typical accompaniment. The concurrent hypomagnesaemia must be corrected for potassium repletion to be effective. IV and oral KCl replacement is required.

Reference: eTG Cardiovascular – 2024 – Electrolyte Disorders; KDIGO 2024