Propofol infusion syndrome (PRIS) is a rare but fatal complication. Which metabolic derangement is the most characteristic biochemical marker and what is the minimum infusion rate below which PRIS risk is acceptably low?

• A Hyperglycaemia; < 4 mg/kg/h
• B Hyponatraemia with low osmolality; < 6 mg/kg/h
• C Respiratory alkalosis with hypocalcaemia; < 2 mg/kg/h
• D Metabolic acidosis with high anion gap and lipemic plasma; < 4 mg/kg/h ✓

Explanation

PRIS is characterised by severe high anion gap metabolic acidosis, rhabdomyolysis, hyperlipaemia (lipemic plasma), renal failure, cardiac arrhythmias, and hepatomegaly. The mechanism involves impaired mitochondrial beta-oxidation of fatty acids. Risk is significantly higher above 4 mg/kg/h for more than 48 hours, particularly in critically ill patients with high catecholamine/glucocorticoid levels. Treatment includes stopping propofol and initiating haemofiltration. PRIS can occur even at lower doses in susceptible individuals.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

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