A type 1 diabetic patient is listed for elective knee arthroscopy. She takes insulin glargine 20 U at night and insulin lispro before meals. What is the most appropriate perioperative insulin management?

• A Withhold all insulin the day before and day of surgery
• B Convert all insulin to intravenous regular insulin starting 48 hours before surgery
• C Give full glargine dose and 25% of lispro with a light breakfast
• D Give 50–80% of the usual basal (glargine) dose the night before; omit bolus lispro; target blood glucose 6–10 mmol/L ✓

Explanation

Current consensus (JBDS, AAGBI guidelines) recommends giving 50–80% of the usual long-acting/basal insulin dose the evening before or morning of surgery to prevent ketoacidosis while minimising hypoglycaemia risk during fasting. Rapid-acting prandial analogues (lispro, aspart) are omitted as the patient is fasted. Target intraoperative glucose is 6–10 mmol/L (108–180 mg/dL). Withholding all insulin risks diabetic ketoacidosis in type 1 diabetes. Preoperative conversion to IV insulin is unnecessary for brief elective procedures.

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

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