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Refractory Hypokalaemia — ESENeph MCQ

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ModerateElectrolyte DisordersRefractory HypokalaemiaESENeph

A 48-year-old man with alcohol use disorder presents with weakness. Bloods show: K+ 2.0 mmol/L, Mg2+ 0.4 mmol/L, Ca2+ 1.85 mmol/L, phosphate 0.6 mmol/L. Despite aggressive IV potassium replacement (80 mmol over 4 hours), serum K+ remains at 2.3 mmol/L. What is the most likely reason for refractory hypokalaemia?

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Correct answer: B — Concurrent hypomagnesaemia preventing potassium repletion

Hypomagnesaemia causes refractory hypokalaemia because magnesium is required for ROMK channel closure in the distal nephron. Without adequate magnesium, potassium continues to be lost in the urine regardless of how much is replaced. Magnesium must be corrected first before potassium can be effectively repleted. Alcohol misuse commonly causes magnesium depletion through poor intake, GI losses, and renal wasting.

Reference: Huang and Kuo 2007 – Magnesium and Potassium; KDIGO Electrolyte Consensus