OSCE — Toxic Alcohols: Methanol & Ethylene Glycol Poisoning

Brief (to candidate)

You will assess a patient with a presentation consistent with Toxic Alcohols: Methanol & Ethylene Glycol Poisoning.
You have 8 minutes to take a focused history, outline examination, investigations, and management including red flags.^[1]

Clinical context

Methanol and ethylene glycol are toxic alcohols that have relatively low toxicity until metabolised by hepatic alcohol dehydrogenase to highly toxic organic acids — methanol to formic acid (prime cause of ocular toxicity; visual impairment from blurred vision to complete blindness) and ethylene glycol to glycolate and oxalate (metabolic acidemia, neurotoxicity, acute kidney injury, hypocalcaemia, calcium oxalate crystalluria). The laboratory signature is a high anion-gap metabolic acidosis with an elevated osmolal gap early in the course; as the parent alcohol is metabolised the osmolal gap falls while the anion gap rises. Start fomepizole on history and anion-gap acidosis while awaiting concentrations; sodium bicarbonate for significant acidosis; intravenous folinic acid in methanol; extracorporeal treatment for EXTRIP severe features.^[1][2][3][4]

Candidate tasks

1. Clarify onset, severity, associated features, and red-flag symptoms.
2. State focused examination priorities.
3. List first-line investigations and any named score/criteria.
4. Give immediate resuscitation steps.
5. Outline definitive management with doses/routes where standard.
6. Name complications and disposition (ward / HDU / theatre / discharge safety-net).
7. Mention one special-population modifier (pregnancy, child, elderly, CKD).^[2]

Examiner checklist

Model outline

Lead with the working diagnosis and life threats. Resuscitate and block alcohol dehydrogenase in the same moment — fomepizole 15 mg/kg load (IV or oral), then 10 mg/kg every 12 h until concentrations are under 30 mg/dL; 1 mg/kg/h continuous infusion during haemodialysis. Give intravenous sodium bicarbonate for significant acidosis and intravenous folinic acid in methanol. Dialyse for EXTRIP severe features (methanol: new vision deficits, pH of 7.15 or lower, anion gap over 24 mmol/L; ethylene glycol: coma, seizures or AKI). Continue antidotes during extracorporeal treatment. Document escalation criteria. A safe candidate is specific, structured, and never delays the antidote for a pending level.^[2][3][4]

References4ShowHide

1. [1]Barceloux DG, Bond GR, Krenzelok EP, Cooper H, Vale JA American Academy of Clinical Toxicology practice guidelines on the treatment of methanol poisoning J Toxicol Clin Toxicol, 2002.PMID 12216995
2. [2]Mégarbane B Treatment of patients with ethylene glycol or methanol poisoning: focus on fomepizole Open Access Emerg Med, 2010.PMID 27147840
3. [3]Roberts DM, Yates C, Megarbane B, et al Recommendations for the role of extracorporeal treatments in the management of acute methanol poisoning: a systematic review and consensus statement Crit Care Med, 2015.PMID 25493973
4. [4]Ghannoum M, Gosselin S, Hoffman RS, et al Extracorporeal treatment for ethylene glycol poisoning: systematic review and recommendations from the EXTRIP workgroup Crit Care, 2023.PMID 36765419