What are the peri‑operative glucose management and medication adjustment recommendations for a patient with diabetes mellitus undergoing anesthesia?

Perioperative Diabetes Management and Anesthesia

Target blood glucose between 90-180 mg/dL (5.0-10.0 mmol/L) throughout the perioperative period using continuous intravenous insulin infusion when needed, while avoiding strict normoglycemia that increases hypoglycemia risk and mortality. 1, 2

Glycemic Targets

Maintain glucose between 90-180 mg/dL (5.0-10.0 mmol/L) perioperatively—this range reduces infection, mortality, and morbidity without increasing dangerous hypoglycemia. 1, 2

• Hyperglycemia >180 mg/dL (10 mmol/L) increases surgical site infections, delayed healing, and mortality. 1
• Strict normoglycemia (80-120 mg/dL) increases severe hypoglycemia rates and possibly mortality without additional benefit. 1
• Moderate control (140-180 mg/dL) represents the optimal balance, decreasing morbidity/mortality by 29-37% compared to poor control. 1
• Postpone elective surgery if glucose >300 mg/dL (16.5 mmol/L) or HbA1c >8%. 1, 2, 3

Preoperative Medication Adjustments

Oral Hypoglycemic Agents

Hold metformin on the day of surgery (can take with dinner the night before) to avoid lactic acidosis risk. 2, 4, 3

Discontinue SGLT2 inhibitors 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis. 2, 4, 3

Hold all other oral agents (sulfonylureas, DPP-4 inhibitors, glinides) the morning of surgery. 1, 2, 3

Insulin Management

Administer 75-80% of usual long-acting insulin analog dose (glargine, detemir, degludec) or 50% of NPH dose on the morning of surgery. 2, 3

If patient uses a personal insulin pump, remove it and immediately initiate continuous IV insulin infusion (IVES) at the start of the procedure. 1

Type 1 diabetics must receive insulin even during fasting to prevent ketoacidosis. 5

Intraoperative Management

Use continuous intravenous insulin infusion (IVES) with ultra-rapid acting analogs for all Type 1 diabetics, Type 2 diabetics requiring insulin, and stress hyperglycemia. 1, 2, 3

Always administer concurrent IV glucose (approximately 4 g/hour, typically 10% dextrose at 40 mL/hour) with insulin infusion. 1, 2

Monitor serum potassium every 4 hours during insulin therapy to prevent insulin-induced hypokalemia. 1, 2

Measure blood glucose every 1-2 hours intraoperatively using venous or arterial samples, not capillary fingersticks. 1, 2

• Capillary readings overestimate glucose levels, especially with vasoconstriction. 1, 3
• A capillary reading of 70 mg/dL (3.8 mmol/L) should be considered hypoglycemia and verified by laboratory measurement. 1, 3

Surgical Scheduling and Fasting

Schedule diabetic patients as the first case of the morning to minimize fasting duration and glycemic disruption. 1, 2, 3

Diabetes does not change usual fasting rules—clear fluids permitted up to 2 hours preoperatively. 1

Avoid prolonged fasting by scheduling early and resuming oral intake as soon as possible postoperatively. 1

Glucose Monitoring Protocol

Measure blood glucose every 1-2 hours intraoperatively and every 2-4 hours during NPO periods. 1, 2, 3

Use arterial or venous blood samples rather than capillary measurements for accuracy. 1, 2, 3

Initiate corrective insulin bolus if glucose exceeds 180 mg/dL (10 mmol/L). 1

Postoperative Management

Transition from IV to subcutaneous basal insulin 2-4 hours before stopping the IV infusion to prevent rebound hyperglycemia. 2, 3

Resume oral diabetes medications with the first postoperative meal when patient is eating and drinking normally. 1, 2, 4

Never use correction-only sliding scale insulin alone without basal insulin postoperatively—this increases complications. 3

Continue glucose monitoring until stable on home regimen with target 100-180 mg/dL. 2, 4, 3

Anesthetic Considerations

Prioritize regional anesthesia when possible—it provides better postoperative pain control and reduces insulin resistance. 1

Use 4 mg dexamethasone (not 8 mg) for PONV prophylaxis combined with another antiemetic, as higher doses worsen hyperglycemia. 1, 6

Implement multimodal analgesia, prevent hypothermia, minimize blood loss, and encourage early ambulation to reduce perioperative insulin resistance. 1

All IV solutions including Ringer's lactate may be used perioperatively. 1

Critical Pitfalls to Avoid

Do not aim for strict normoglycemia (<100 mg/dL)—this increases hypoglycemia without improving outcomes. 1, 2

Do not confuse metformin (hold day of surgery) with SGLT2 inhibitors (stop 3-4 days prior). 4

Do not rely on capillary glucose readings in vasoconstricted patients—verify with laboratory samples. 1, 3

Do not stop insulin in Type 1 diabetics even during fasting—ketoacidosis risk is high. 5

Do not discharge ambulatory patients with glucose >300 mg/dL (16.5 mmol/L)—admit for IV insulin therapy. 1