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Diabetes Insipidus in Brainstem Death — FRCA Final MCQ

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ModerateIntensive Care MedicineDiabetes Insipidus in Brainstem DeathFRCA Final

A 60-year-old woman is in ICU following a severe subarachnoid haemorrhage. She is brainstem dead and organ donation is planned. Her serum sodium rises to 158 mmol/L and her urine output increases to 500 mL/hr with a urine specific gravity of 1.002. What is the most likely diagnosis and treatment?

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Correct answer: C — Diabetes insipidus – desmopressin (DDAVP)

Diabetes insipidus (DI) is common following brainstem death due to loss of ADH (vasopressin) secretion from the posterior pituitary. It presents with large volumes of dilute urine (>4 mL/kg/hr, specific gravity <1.005, urine osmolality <200 mOsm/kg), rising serum sodium, and hypernatraemia. Treatment: IV desmopressin (DDAVP) 1-4 mcg IV/SC, with fluid replacement matched to urine output. In the context of organ donation, DI management is critical to maintain donor organ perfusion and prevent hypernatraemic organ damage.

Reference: NICE – 2016 – CG135 Organ donation; NHSBT – 2023 – Donor optimisation guidelines