Preoperative Insulin Adjustments
Reduce basal insulin by 25% the evening before surgery to achieve optimal perioperative glucose control while minimizing hypoglycemia risk. 1, 2
Medication Management Before Surgery
Long-Acting Basal Insulin (Evening Before Surgery)
- Administer 75% of the usual dose (i.e., reduce by 25%) of long-acting insulin analogs (glargine, detemir, degludec) the evening before surgery 1, 2
- This 25% reduction strategy achieves better perioperative glucose targets with significantly lower hypoglycemia rates compared to usual dosing 1
Morning of Surgery Insulin Adjustments
- NPH insulin: Give 50% of usual morning dose 1
- Long-acting analogs: Give 75-80% of usual dose if typically administered in the morning 1
- Insulin pumps: Adjust basal rates based on diabetes type and clinical judgment 1
- Hold all bolus/prandial insulin (rapid-acting or short-acting) on the morning of surgery since patient will be NPO 1
Non-Insulin Medications to Discontinue
- SGLT2 inhibitors: Stop 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis, a life-threatening complication that can occur even with normal glucose levels 1, 2
- Metformin: Hold on the day of surgery 1
- All other oral glucose-lowering agents: Hold the morning of surgery 1
- GLP-1 receptor agonists: Limited data exist, but caution is warranted due to delayed gastric emptying concerns 1
Preoperative Optimization Targets
A1C Goals
- Target A1C <8% for elective surgeries whenever possible to reduce mortality, infection rates, and surgical complications 1, 2
- Consider delaying elective surgery if A1C is significantly elevated to allow optimization 1
Blood Glucose Targets
- Perioperative target: 100-180 mg/dL (5.6-10.0 mmol/L) within 4 hours of surgery 1, 2
- Do not pursue stricter targets (<100 mg/dL or 80-180 mg/dL range) as they increase hypoglycemia risk without improving outcomes 1, 2
Intraoperative and Immediate Preoperative Monitoring
- Monitor blood glucose at least every 2-4 hours while patient is NPO 1
- Administer short- or rapid-acting insulin as needed to maintain 100-180 mg/dL target 1
- Do not use CGM alone for glucose monitoring during surgery; point-of-care testing is required 1, 2
Critical Pitfalls to Avoid
- Never continue full basal insulin doses the night before surgery—the 25% reduction is evidence-based and prevents hypoglycemia 1, 2
- Never continue SGLT2 inhibitors within 3-4 days of surgery due to ketoacidosis risk, even with euglycemia 1, 2
- Never give morning bolus insulin when patient is NPO—this causes severe hypoglycemia 1
- Never target glucose <100 mg/dL perioperatively—this increases hypoglycemia without benefit 1, 2
Special Considerations
Type 1 Diabetes
- Patients require continuous insulin replacement at all times to prevent diabetic ketoacidosis 3
- Even with NPO status, basal insulin must be continued (at reduced dose as above) 3
Patients on Glucocorticoids
- If patient is on chronic steroids, anticipate need for substantial insulin increases (40-60% or more) in addition to basal insulin adjustments 1, 2
- Glucocorticoids induce hyperglycemia in 56-86% of patients, increasing mortality and infection risk if untreated 1, 2