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SIADH – fluid restriction — RACP Paediatrics MCQ

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ModerateNephrologySIADH – fluid restrictionRACP Paediatrics

A 6-year-old post-meningitis has a serum sodium of 125 mmol/L. She is euvolaemic with no oedema or dehydration. Urine is concentrated (osmolality 550 mOsm/kg) with high urine sodium (80 mmol/L). ADH is inappropriately elevated. What is the most appropriate fluid management?

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Correct answer: E — Fluid restriction to 50% maintenance

SIADH (euvolaemic hyponatraemia with concentrated urine, high urine sodium, and inappropriately elevated ADH) is best managed with fluid restriction (typically 50-60% of maintenance). Hypertonic saline is reserved for symptomatic hyponatraemia (seizures, encephalopathy). The underlying cause (meningitis) should be treated concurrently.

Reference: RCH Melbourne – 2023 – Hyponatraemia CPG; RACP Paediatric Curriculum – Nephrology