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Early ethylene glycol poisoning — MRCEM SBA MCQ

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EasyToxicology and environmental emergenciesEarly ethylene glycol poisoningMRCEM SBA

A 41-year-old mechanic attends the emergency department three hours after deliberately drinking several mouthfuls of an engine coolant labelled as containing ethylene glycol. He feels nauseated but is alert and haemodynamically stable. He reports no alcohol ingestion. Arterial pH is 7.38, bicarbonate is 24 mmol/L and creatinine is 80 µmol/L. Serum sodium is 140 mmol/L, glucose 5 mmol/L and urea 5 mmol/L; measured serum osmolality is 328 mOsm/kg. An urgent ethylene glycol assay has been requested but will not be available immediately. Fomepizole is available. Which management plan is most appropriate now?

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Correct answer: C — Start intravenous fomepizole while awaiting the ethylene glycol assay.

The labelled coolant provides a credible exposure, and the calculated osmolality is approximately 290 mOsm/kg (2 × sodium + glucose + urea), giving an osmolar gap of approximately 38 mOsm/kg. Early after ethylene glycol ingestion, the parent compound can raise the osmolar gap before its metabolism produces an anion-gap acidosis. A normal pH therefore offers no reassurance. UK product information recommends starting fomepizole as soon as poisoning is suspected, without waiting for the ethylene glycol assay. ([medicines.org.uk](https://www.medicines.org.uk/emc/product/101333/smpc)) **A** delays an antidote despite compelling early evidence; serial tests remain necessary after treatment begins. **B** addresses clinically significant acidosis, which is absent, but does not prevent formation of toxic metabolites. **D** may become necessary with severe acidosis or renal impairment; neither is present, so it is not the immediate priority. **E** is a plausible alternative alcohol dehydrogenase-blocking treatment if fomepizole cannot be obtained promptly, but fomepizole is available here. Continue monitored assessment, serial acid–base and renal testing, and specialist toxicology advice while the assay is processed. ([medicines.org.uk](https://www.medicines.org.uk/emc/product/101333/smpc))

Reference: Fomepizole Waymade 1 g/ml concentrate for solution for infusion — Summary of Product Characteristics, sections 4.1–4.2 (10 September 2025) — https://www.medicines.org.uk/emc/product/101333/smpc Gloucestershire Hospitals NHS Foundation Trust — Ethylene Glycol/Methanol (Update date not stated on page) — https://www.gloshospitals.nhs.uk/our-services/services-we-offer/pathology/tests-and-investigations/ethylene-glycolmethanol/ Fomepizole Waymade — Summary of Product Characteristics, section 4.2 (10 September 2025) — https://www.medicines.org.uk/emc/product/101333/smpc