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Hyponatraemia — RACP Adult Medicine MCQ

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ModerateGeneral Internal MedicineHyponatraemiaRACP Adult Medicine

A 60-year-old man is found to have a serum sodium of 115 mmol/L. He is asymptomatic. Serum osmolality is 250 mOsm/kg, urine osmolality is 600 mOsm/kg, and urine sodium is 45 mmol/L. He appears euvolaemic. TSH and cortisol are normal. What is the maximum recommended rate of sodium correction in the first 24 hours?

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Correct answer: A — 6–8 mmol/L

Current guidelines recommend limiting sodium correction to 6–8 mmol/L in any 24-hour period to minimise the risk of osmotic demyelination syndrome (ODS/central pontine myelinolysis). European guidelines suggest a target of ≤10 mmol/L in the first 24 hours and ≤8 mmol/L in subsequent 24-hour periods. Lower limits (≤8 mmol/L/24 hours) are recommended for patients at higher risk of ODS (chronic hyponatraemia, hypokalaemia, malnutrition, alcoholism).

Reference: eTG – 2025 – Endocrinology; European Hyponatraemia Guideline Group – 2014