A diabetic patient on metformin requires an elective procedure under general anaesthesia involving iodinated contrast. Which of the following is the recommended perioperative management regarding metformin?

• A Continue metformin throughout; there is no interaction with contrast or anaesthesia
• B Replace metformin with insulin 1 week preoperatively
• C Double the metformin dose perioperatively to counteract surgical stress hyperglycaemia
• D Withhold metformin 48 h before contrast use and resume only after confirming normal renal function ✓

Explanation

Metformin is withheld 48 hours before iodinated contrast administration because contrast-induced nephropathy can cause acute renal impairment, leading to metformin accumulation and life-threatening lactic acidosis. Metformin should not be restarted until renal function is reassessed and found normal (creatinine at 48 h post-procedure). For non-contrast procedures, metformin is withheld on the day of surgery due to the risk of lactic acidosis from tissue hypoperfusion under anaesthesia.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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