skip to main content

Cyclophosphamide Hydration Fluid Choice — ESENeph MCQ

Instant feedback + full explanation. One question, done properly.

ModerateElectrolyte DisordersCyclophosphamide Hydration Fluid ChoiceESENeph

A 48-year-old woman develops severe hyponatraemia (Na+ 118 mmol/L) during her ANCA vasculitis treatment with IV Cyclophosphamide. She received 3 L of 5% dextrose as part of the hydration protocol. Her serum and urine biochemistry confirm SIADH. What should the hydration fluid be?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: C — 0.9% normal saline as the next step

5% dextrose is effectively free water once the glucose is metabolised, which worsens hyponatraemia in SIADH. When hydrating for Cyclophosphamide (to prevent haemorrhagic cystitis), 0.9% normal saline should be used rather than dextrose solutions. This provides the necessary urine flow to wash out acrolein (the bladder-toxic metabolite) without contributing free water that exacerbates the Cyclophosphamide-induced SIADH. Total fluid volume should be limited to what is necessary for bladder protection.

Reference: https://guidelines.ukkidney.org