What are the pre-anesthesia considerations for patients taking Oral Hypoglycemic Agents (OHAs) and insulin?

Pre-Anesthesia Considerations for Patients Taking OHAs and Insulin

For patients with diabetes undergoing surgery, metformin should be held on the day of surgery, SGLT2 inhibitors discontinued 3-4 days before surgery, and all other oral hypoglycemic agents held the morning of surgery, while insulin doses should be adjusted to 50% of NPH dose or 75-80% of long-acting analog insulin. 1

Blood Glucose Targets and Preoperative Assessment

• The target blood glucose range in the perioperative period should be 100-180 mg/dL (5.6-10.0 mmol/L) within 4 hours of surgery 1
• The A1C goal for elective surgeries should be <8% (<64 mmol/L) whenever possible 1
• A preoperative risk assessment should be performed for patients with diabetes who are at high risk for ischemic heart disease and those with autonomic neuropathy or renal failure 1
• CGM (continuous glucose monitoring) should not be used alone for glucose monitoring during surgery 1

Management of Oral Hypoglycemic Agents (OHAs)

• Metformin should be held on the day of surgery 1
• SGLT2 inhibitors must be discontinued 3-4 days before surgery due to risk of euglycemic ketoacidosis 1
• All other oral glucose-lowering agents should be held the morning of surgery or procedure 1
• For ambulatory surgery patients, continuing OHAs preoperatively may result in lower perioperative blood glucose levels (138 mg/dL vs 156 mg/dL), but this approach is not recommended in current guidelines 2

Insulin Management

• For patients on NPH insulin, give half of the usual dose on the morning of surgery 1
• For patients on long-acting insulin analogs, give 75-80% of the usual dose 1
• For patients using insulin pumps, adjust basal rates based on the type of diabetes and clinical judgment 1
• Compared with usual dosing, a reduction by 25% of basal insulin given the evening before surgery is more likely to achieve perioperative blood glucose goals with a lower risk for hypoglycemia 1
• In non-cardiac general surgery patients, basal insulin plus premeal short- or rapid-acting insulin (basal-bolus) coverage has been associated with improved glycemic outcomes and lower rates of perioperative complications compared with correction-only insulin coverage 1

Intraoperative Monitoring and Management

• Monitor blood glucose at least every 2-4 hours while the patient takes nothing by mouth 1
• Dose with short- or rapid-acting insulin as needed to maintain target glucose range 1
• Stricter perioperative glycemic goals (tighter than 80-180 mg/dL) are not advised as they may not improve outcomes and are associated with more hypoglycemia 1

Special Considerations

• There are limited data on the safe use and influence of GLP-1 receptor agonists on glycemia and delayed gastric emptying in the perioperative period 1
• Surgical stress and counterregulatory hormone release increase the risk of hyperglycemia, which is associated with increased mortality, infection, and length of stay 1
• Patients receiving glucocorticoids during the perioperative period may require additional insulin to manage hyperglycemia 1
• Hypoglycemia is the most common adverse reaction of insulin therapies and may lead to unconsciousness, convulsions, and temporary or permanent impairment of brain function 3

Common Pitfalls and How to Avoid Them

• Failing to discontinue SGLT2 inhibitors 3-4 days before surgery can lead to euglycemic diabetic ketoacidosis 1
• Not reducing insulin doses appropriately can lead to hypoglycemia during the perioperative period 1, 3
• Inadequate glucose monitoring during the perioperative period can result in undetected hypo- or hyperglycemia 1
• Using correction-only insulin without basal insulin can lead to worse glycemic outcomes and higher rates of perioperative complications 1
• Failing to account for the effects of surgical stress on glucose metabolism can lead to hyperglycemia 1