How long before surgery should oral hypoglycemics (oral anti-diabetic medications) for type 2 diabetes be held?

Perioperative Management of Oral Hypoglycemics for Type 2 Diabetes

Most oral hypoglycemic medications should be held on the morning of surgery, with the exception of SGLT2 inhibitors which must be discontinued 3-4 days before surgery. 1

Specific Timing for Different Classes of Oral Hypoglycemics

Day of Surgery Discontinuation:

• Metformin: Hold on the day of surgery 1
• Sulfonylureas: Hold on the morning of surgery 1
• Meglitinides: Hold on the morning of surgery 1
• DPP-4 inhibitors: Hold on the morning of surgery 1
• Thiazolidinediones: Hold on the morning of surgery 1
• Alpha-glucosidase inhibitors: Hold on the morning of surgery 1
• GLP-1 receptor agonists: Hold on the morning of surgery (limited data on perioperative use) 1

Special Considerations:

• SGLT2 inhibitors: Must be discontinued 3-4 days before surgery 1

Rationale and Evidence

The recommendation to hold most oral hypoglycemics on the morning of surgery is based on several factors:

1. Risk of hypoglycemia: Fasting before surgery combined with the continued action of hypoglycemic medications increases risk of hypoglycemia, which can lead to significant morbidity 2

2. Surgical stress response: Surgery triggers counterregulatory hormone release that increases blood glucose levels, potentially counteracting the effects of hypoglycemic medications 1

3. Unpredictable absorption: Altered gastrointestinal function perioperatively can affect drug absorption 3

4. Blood glucose targets: The perioperative blood glucose goal should be 100-180 mg/dL (5.6-10.0 mmol/L) within 4 hours of surgery 1

SGLT2 inhibitors require earlier discontinuation (3-4 days before surgery) due to their unique mechanism of action and risk of euglycemic diabetic ketoacidosis, which could be exacerbated by surgical stress and fasting 1.

Monitoring and Management

• Monitor blood glucose every 2-4 hours while the patient takes nothing by mouth 1
• Use short- or rapid-acting insulin as needed for hyperglycemia 1
• Target perioperative blood glucose of 100-180 mg/dL (5.6-10.0 mmol/L) 1
• Avoid stricter glycemic targets as they increase hypoglycemia risk without improving outcomes 1

Insulin Adjustments

For patients also on insulin therapy:

• Give one-half of NPH dose or 75-80% of long-acting analog insulin dose 1
• Adjust insulin pump basal rates based on clinical judgment 1
• Consider that a 25% reduction in basal insulin the evening before surgery may better achieve perioperative glucose targets with lower hypoglycemia risk 1

Common Pitfalls to Avoid

1. Not discontinuing SGLT2 inhibitors early enough: This can lead to euglycemic ketoacidosis, a serious complication that may be difficult to detect

2. Continuing metformin too close to surgery: While newer guidelines recommend holding only on the day of surgery 1, some older practices suggested stopping 48 hours prior 3 to reduce lactic acidosis risk, especially in patients with renal impairment

3. Ignoring the A1C level: The A1C goal for elective surgeries should be <8% whenever possible 1

4. Inadequate glucose monitoring: Failure to monitor glucose levels frequently during the perioperative period can lead to undetected hypo- or hyperglycemia

5. Overly aggressive glucose control: Targeting blood glucose levels below 100 mg/dL increases hypoglycemia risk without improving outcomes 1

By following these evidence-based recommendations for the perioperative management of oral hypoglycemics, clinicians can minimize the risks of both hypoglycemia and hyperglycemia, thereby reducing perioperative morbidity and mortality in patients with type 2 diabetes.