Risks of Surgery with Hyperglycemia and Pre-operative Management
For surgery scheduled tomorrow, reduce the patient's basal insulin by 25% the evening before surgery, target blood glucose 100-180 mg/dL perioperatively, and use short-acting insulin every 2-4 hours as needed to maintain this range. 1
Risks of Performing Surgery with Hyperglycemia
Hyperglycemia during the perioperative period significantly increases mortality, infection rates, and hospital length of stay. 1
Surgical stress and counterregulatory hormones exacerbate hyperglycemia, creating a dangerous cycle that affects up to 20% of general surgery patients with diabetes and 23-60% with prediabetes or undiagnosed diabetes 1
In patients WITHOUT diabetes, perioperative hyperglycemia carries even greater risk than in diabetic patients - there is a dose-response relationship where each 40 mg/dL increase in glucose over 70-179 mg/dL increases postoperative infection risk by 40% 2
Patients without diabetes who develop hyperglycemia perioperatively have 1.6 times higher odds of adverse events when glucose reaches ≥180 mg/dL, while paradoxically, diabetic patients with similar glucose levels show no increased risk (likely due to chronic adaptation and more aggressive insulin treatment) 2
Even moderate preoperative hyperglycemia (100-139 mg/dL) in non-diabetic patients increases postoperative infection rates to 9.33% compared to 5.62% in those with glucose 70-99 mg/dL 3
Pre-operative Management for Surgery Tomorrow
Immediate Glycemic Targets
Target A1C <8% for elective surgeries whenever possible, and blood glucose 100-180 mg/dL within 4 hours of surgery. 1
- Do NOT pursue stricter targets than 80-180 mg/dL, as tighter control does not improve outcomes and significantly increases hypoglycemia risk 1
Medication Adjustments Tonight (Evening Before Surgery)
Reduce basal insulin by 25% from the usual evening dose - this approach is more likely to achieve target perioperative glucose levels with lower hypoglycemia risk compared to usual dosing 1
- For patients on long-acting insulin analogs: give 75-80% of usual dose 1
- For patients on NPH insulin: give 50% of usual dose 1
- For insulin pump users: continue basal rates but prepare backup plan 1
Medication Adjustments Day of Surgery
Hold all oral glucose-lowering agents the morning of surgery 1
- SGLT2 inhibitors should have been discontinued 3-4 days before surgery (if not already done, document the increased risk of euglycemic ketoacidosis) 1
- Hold metformin on the day of surgery 1
- Hold all other oral agents the morning of surgery 1
Monitoring and Insulin Coverage
Monitor blood glucose every 2-4 hours while NPO and dose with short- or rapid-acting insulin as needed to maintain 100-180 mg/dL 1
- Do NOT rely on continuous glucose monitoring (CGM) alone during surgery - point-of-care testing is required 1
- Use basal-bolus insulin coverage (basal insulin plus premeal short/rapid-acting insulin) rather than correction-only sliding scale - this approach improves glycemic outcomes and reduces perioperative complications in noncardiac general surgery 1
Critical Pitfalls to Avoid
The most common error is undertreatment of hyperglycemia in non-diabetic patients - these patients are less likely to receive insulin at each glucose level despite having higher complication risks 2
- Avoid overly aggressive glucose lowering - hypoglycemia carries significant risks including neuronal damage and cognitive deficits 4
- GLP-1 receptor agonists have limited safety data regarding delayed gastric emptying in the perioperative period - use caution 1
- If patient received dexamethasone or other glucocorticoids, anticipate significantly higher insulin requirements (potentially 40-60% increases) 1
Pre-operative Risk Assessment
Perform cardiovascular risk assessment in diabetic patients at high risk for ischemic heart disease, and those with autonomic neuropathy or renal failure 1
- This is particularly important given that surgical stress compounds existing cardiovascular risks in diabetic patients 1