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Severe symptomatic hyponatraemia due to SIADH — SCE Acute Medicine MCQ

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ModerateDiabetes and endocrine medicineSevere symptomatic hyponatraemia due to SIADHSCE Acute Medicine

A 66-year-old man with small-cell lung cancer develops confusion and a generalised seizure. Sodium is 112 mmol/L, serum osmolality is low, urine osmolality is 620 mOsm/kg and urine sodium is 78 mmol/L. He is clinically euvolaemic. What is the most appropriate next step in management?

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Correct answer: A — Give hypertonic saline with close sodium monitoring

Seizure with severe hyponatraemia is a medical emergency requiring hypertonic saline to raise sodium safely by a small amount, followed by controlled correction. Fluid restriction alone is too slow for severe symptoms. Over-rapid correction risks osmotic demyelination, especially in chronic or uncertain-duration hyponatraemia.

Reference: https://www.nice.org.uk/guidance#acute-medicine-order-88-1