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Hypernatraemic dehydration due to gastroenteritis — MRCEM SBA MCQ

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HardPaediatric emergenciesHypernatraemic dehydration due to gastroenteritisMRCEM SBA

A 16-month-old girl presents with three days of vomiting and watery diarrhoea. She has dry mucous membranes, sunken eyes and reduced urine output. She is alert but irritable, with warm peripheries, a capillary refill time of 2 seconds and a blood pressure of 94/60 mmHg. Small, frequent volumes of oral rehydration solution have been tried, followed by nasogastric administration, but she persistently vomits both. Her plasma sodium is 161 mmol/l and blood glucose is normal. Which rehydration plan is most appropriate now?

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

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Correct answer: E — Admit for expert-guided intravenous 0.9% sodium chloride; replace the deficit over 48 hours with frequent plasma sodium monitoring.

This child has clinical dehydration and marked hypernatraemia, but her preserved perfusion does not indicate shock. Persistent vomiting despite both oral and nasogastric rehydration makes intravenous treatment appropriate. NICE advises urgent expert input for intravenous management of hypernatraemic dehydration, an isotonic solution for deficit replacement and maintenance, replacement of the deficit typically over 48 hours, and frequent sodium measurements. The intended fall in sodium is less than 0.5 mmol/l per hour. She requires admission for this monitored treatment. ([nice.org.uk](https://www.nice.org.uk/guidance/CG84/chapter/recommendations)) A adds a rapid bolus, which is appropriate for suspected or confirmed shock, not for the perfused child described. B would be a reasonable next step if oral rehydration alone had failed, but nasogastric solution has also been persistently vomited. C selects an appropriate isotonic fluid but replaces the deficit too rapidly for presenting hypernatraemia. D allows slow replacement but selects a hypotonic rather than the recommended isotonic solution. Hypernatraemia itself does not preclude oral or nasogastric rehydration; failure of both routes is the decisive reason to move to intravenous fluids here. ([nice.org.uk](https://www.nice.org.uk/guidance/CG84/chapter/recommendations))

Reference: NICE CG84, recommendations 1.3.2.1 and 1.3.3.1–1.3.3.2 (22 April 2009) — https://www.nice.org.uk/guidance/cg84/chapter/Recommendations NICE CG84, recommendation 1.3.3.6 (22 April 2009) — https://www.nice.org.uk/guidance/cg84/chapter/Recommendations