Perioperative Hypoglycemic Agent Management
Insulin is the preferred hypoglycemic agent for patients undergoing surgery, specifically using a basal-bolus regimen (basal insulin plus premeal short- or rapid-acting insulin) rather than correction-only insulin, as this approach improves glycemic outcomes and reduces perioperative complications in noncardiac general surgery patients. 1, 2
Preoperative Medication Management
Oral Hypoglycemic Agents - Discontinuation Timeline
SGLT2 inhibitors (canagliflozin, dapagliflozin, empagliflozin) must be discontinued 3-4 days before surgery to prevent life-threatening euglycemic diabetic ketoacidosis, which can occur even with normal glucose levels 1, 2, 3. This is the most critical medication adjustment, as euglycemic DKA can develop even when glucose appears normal, and the risk persists even after 72 hours of discontinuation 3.
Metformin should be held only on the day of surgery 1, 2, 4. Current guidelines support this less restrictive approach compared to historical practices that recommended 48-hour discontinuation 5.
All other oral hypoglycemic agents (sulfonylureas, DPP-4 inhibitors, thiazolidinediones, meglitinides) should be held on the morning of surgery 1, 3, 4.
Insulin Dose Adjustments
Reduce basal insulin by 25% the evening before surgery - this approach achieves better perioperative glucose control with significantly lower hypoglycemia risk compared to usual dosing 1, 2, 4.
For morning-of-surgery dosing:
- NPH insulin: Give 50% of the usual dose 1, 4
- Long-acting insulin analogs (glargine, detemir): Give 75-80% of the usual dose 1, 4, 6
- Insulin pumps: Adjust basal rates based on clinical judgment 1
Intraoperative Insulin Management
Target blood glucose 100-180 mg/dL within 4 hours of surgery 1, 2, 4. Do not pursue stricter targets (<80-180 mg/dL), as they do not improve outcomes and significantly increase hypoglycemia risk 1, 2.
Monitor blood glucose at least every 2-4 hours while the patient is NPO 1, 2, 4.
Administer short- or rapid-acting insulin as needed to maintain target range 1, 2, 4. For critically ill patients or those with significant metabolic derangements, intravenous insulin infusion at 1-2 units per hour offers more predictable absorption and ability to rapidly titrate compared to subcutaneous sliding scale insulin 7.
Postoperative Insulin Regimen
Use basal-bolus insulin coverage (basal insulin plus premeal short/rapid-acting insulin) rather than correction-only sliding scale insulin 1, 2. This is a critical distinction - correction-only insulin without basal coverage is associated with worse glycemic outcomes and higher complication rates in noncardiac general surgery 1, 2.
Continue monitoring glucose every 2-4 hours while NPO and maintain the 100-180 mg/dL target 2, 4.
Special Clinical Situations
Glucocorticoid-Induced Hyperglycemia
Patients receiving perioperative glucocorticoids require substantial increases in prandial and correction insulin (40-60% or more) in addition to basal insulin 2. Glucocorticoids induce hyperglycemia in 56-86% of hospitalized patients, increasing mortality and morbidity risk through infections and cardiovascular events 1, 2.
Transition from IV to Subcutaneous Insulin
Administer basal insulin 2-4 hours before stopping IV insulin to prevent rebound hyperglycemia and recurrent ketoacidosis in patients with DKA or hyperglycemic hyperosmolar state 1, 2.
Critical Pitfalls to Avoid
Never continue SGLT2 inhibitors within 3-4 days of surgery - this poses unacceptable risk of euglycemic DKA that can be fatal 2, 3.
Never use correction-only insulin without basal insulin in general surgery patients - this is associated with significantly worse outcomes 1, 2.
Never pursue glucose targets <100 mg/dL perioperatively - this increases hypoglycemia without clinical benefit 1, 2.
Never stop IV insulin without prior subcutaneous basal insulin administration - this causes rebound hyperglycemia and potential ketoacidosis 2.
Never fail to adjust insulin for glucocorticoid therapy - untreated steroid-induced hyperglycemia leads to severe complications 2.
Preoperative Optimization
Target A1C <8% for elective surgeries to reduce surgical risk, mortality, and infection rates 1, 2, 4. Some institutions have A1C cutoffs for elective procedures and optimization programs to lower A1C before surgery 1.
Perform preoperative risk assessment for patients at high risk for ischemic heart disease and those with autonomic neuropathy or renal failure 1, 4.
Insulin Formulations for Perioperative Use
Long-acting insulin analogs like glargine can be appropriately administered for basal coverage throughout the surgical period 7. Glargine is administered subcutaneously once daily at the same time each day, should not be diluted or mixed with other insulins, and injection sites should be rotated to reduce lipodystrophy risk 6.
Short-acting or rapid-acting insulin analogs provide flexibility for premeal coverage and treating marked hyperglycemia, though timing of meal delivery in hospitalized patients may increase hypoglycemia risk if insulin cannot be given immediately before meals 8.