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Normal Sodium 135-145 — FRCA Primary MCQ

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HardPhysiology - Endocrine & MetabolicNormal Sodium 135-145FRCA Primary

A stable 70 kg postoperative adult receives 3 L of 5% glucose over 24 hours as sole maintenance. Serum sodium falls from 140 to 128 mmol/L. What is the best next step?

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Correct answer: D — Reassess intravenous fluids and review volume status with the electrolyte trend

The best answer is “Reassess intravenous fluids and review volume status with the electrolyte trend”. A fall in sodium during IV fluid therapy requires reassessment of fluid status, fluid balance, laboratory results and the type, rate and volume prescribed. The patient is stable and no neurological symptoms are stated, so a reflex hypertonic-saline response is not justified. Continuing an excessive hypotonic regimen without review risks worsening iatrogenic hyponatraemia.

Reference: NICE CG174, Intravenous fluid therapy in adults in hospital: https://www.nice.org.uk/guidance/cg174/chapter/Recommendations