What is the treatment for hyperglycemia (high blood sugar) during an operation?

Treatment of Intraoperative Hyperglycemia

For very high blood sugars during surgery, initiate continuous intravenous insulin infusion (IVES) immediately, targeting blood glucose between 90-180 mg/dL (5-10 mmol/L), as this approach reduces perioperative morbidity and mortality in both diabetic and non-diabetic patients. 1

Immediate Management Algorithm

When to Start IV Insulin Intraoperatively

• Start continuous IV insulin infusion for any patient with intraoperative hyperglycemia >180 mg/dL (10 mmol/L), regardless of diabetic status 1
• Type 1 diabetics and insulin-dependent Type 2 diabetics require IVES for all surgical procedures to prevent ketoacidosis 1
• Stress hyperglycemia (non-diabetic patients with elevated glucose) also requires IVES during surgery 1

IV Insulin Dosing Protocol

• Begin with 0.5-1 units/hour IV insulin infusion and titrate based on hourly blood glucose monitoring 2, 3
• Check blood glucose every 30-60 minutes during active titration, then hourly once stable 3
• Target range: 90-180 mg/dL (5-10 mmol/L) during the intraoperative period 1
• Avoid strict normoglycemia (<90 mg/dL) as this significantly increases hypoglycemia risk without additional benefit 1

Critical Monitoring During Surgery

• Monitor blood glucose hourly minimum during IV insulin infusion 3
• Increase monitoring to every 30 minutes if glucose is unstable or changing rapidly 3
• Check for ketosis immediately if glucose >300 mg/dL (16.5 mmol/L) in any diabetic patient on insulin 1, 4

Why This Matters for Patient Outcomes

Intraoperative hyperglycemia is an independent predictor of mortality and morbidity, even in non-diabetic patients undergoing cardiac surgery 5. Each 1 mmol/L increase in peak glucose during cardiopulmonary bypass increases mortality risk by 12-20% 5. Poor intraoperative glycemic control (defined as four consecutive glucose readings >200 mg/dL despite insulin) increases the odds of severe postoperative complications 7-fold 6.

Hyperglycemia impairs host defenses by decreasing polymorphonuclear leukocyte function, chemotaxis, and phagocytic activity, directly increasing infection risk 7. This translates to delayed wound healing and increased surgical site infections 1.

Critical Pitfalls to Avoid

• Never use sliding-scale insulin alone intraoperatively—it is reactive rather than proactive and provides no basal coverage 3
• Do not tolerate glucose >180 mg/dL thinking it's "normal stress response"—this outdated approach increases complications 1, 7
• Never abruptly stop IV insulin—this causes rebound hyperglycemia and potential ketoacidosis in Type 1 diabetics 1
• Do not ignore hyperglycemia in non-diabetic patients—they have the same increased mortality risk as diabetics 5

Severe Hyperglycemia (>300 mg/dL / 16.5 mmol/L)

If glucose exceeds 300 mg/dL intraoperatively, immediately check for ketosis (ketonuria or ketonaemia) 1, 4:

• Ketosis absent (ketonuria 0, ketonaemia <0.5 mmol/L): Give 6 units rapid-acting insulin IV bolus, increase IV insulin infusion rate, ensure adequate hydration 1
• Mild ketosis (ketonuria 1+, ketonaemia 0.5-1.5 mmol/L): Give 6 units rapid-acting insulin IV bolus, increase infusion rate, recheck glucose and ketones in 1 hour 1
• Significant ketosis (ketonuria 2+, ketonaemia >1.5 mmol/L): Consider ICU transfer for aggressive IV insulin therapy and management of impending ketoacidosis 1

Transition Planning

Do not stop IV insulin until the patient is eating and subcutaneous insulin has been administered 1. The transition requires:

• Calculate total 24-hour IV insulin dose from the infusion 1
• Give half this total dose as long-acting basal insulin subcutaneously (e.g., glargine or detemir) 1
• Divide the other half into three equal doses of rapid-acting insulin with meals 1
• Administer the first subcutaneous basal insulin dose, then continue IV insulin for 1-2 hours before discontinuing to ensure overlap 1