Propofol Infusion Syndrome — FRCA Final MCQ

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ModerateIntensive Care MedicinePropofol Infusion SyndromeFRCA Final

A 70 kg adult has been sedated in the intensive care unit for 72 hours with propofol 20 mg/ml at 17.5 ml/hour. He develops an otherwise unexplained metabolic acidosis, hyperkalaemia, markedly elevated creatine kinase, lipaemic plasma and new cardiac arrhythmias. What is the most likely diagnosis?

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Correct answer: B — Propofol infusion syndrome

The diagnosis is propofol infusion syndrome. The calculated infusion rate is 5 mg/kg/hour for 72 hours, exceeding the exposure commonly associated with PRIS: more than 4 mg/kg/hour for more than 48 hours. The characteristic constellation is otherwise unexplained metabolic acidosis, rhabdomyolysis with hyperkalaemia, hyperlipidaemia and cardiac arrhythmias or failure. Mitochondrial energy failure, involving impaired fatty-acid oxidation and electron transport, is implicated. Propofol must be stopped immediately and replaced with another sedative; severe acidosis, hyperkalaemia, renal failure and cardiovascular collapse require organ support, potentially including renal replacement therapy. Malignant hyperthermia usually follows triggering anaesthetics and causes hypercapnia, rigidity and hyperthermia. Serotonin syndrome causes clonus and hyperreflexia, whereas neuroleptic malignant syndrome causes rigidity after dopamine antagonism. Diabetic ketoacidosis requires hyperglycaemia and ketonaemia and does not explain this exposure-related multisystem pattern.

Reference: Aspen Pharma Trading Ltd. Propofol 20 mg/ml (2%) emulsion for injection or infusion, Summary of Product Characteristics, sections 4.2 and 4.4, text revised August 2025. https://www.medicines.org.uk/emc/product/1365/smpc