How to manage blood glucose levels on the day of surgery?

Perioperative Blood Glucose Management on Day of Surgery

On the day of surgery, hold metformin and all other oral diabetes medications in the morning, discontinue SGLT2 inhibitors 3-4 days prior, reduce long-acting basal insulin to 75-80% of usual dose (or 50% of NPH), and maintain blood glucose between 100-180 mg/dL with monitoring every 2-4 hours while NPO, using short- or rapid-acting insulin as needed. 1, 2

Medication Management Before Surgery

Oral Medications

• Hold metformin on the day of surgery only 1, 3
• Discontinue SGLT2 inhibitors (canagliflozin, dapagliflozin, empagliflozin) 3-4 days before surgery to prevent life-threatening euglycemic diabetic ketoacidosis, which can occur even with normal glucose levels 1, 2, 3
• Hold all other oral hypoglycemic agents (sulfonylureas, DPP-4 inhibitors, thiazolidinediones, meglitinides) on the morning of surgery 1, 3

Insulin Adjustments

• Give 75-80% of usual long-acting insulin analog (glargine, detemir, degludec) dose on the evening before or morning of surgery 1, 2
• Give 50% of usual NPH insulin dose if this is the patient's basal insulin 1
• Reducing basal insulin by 25% the evening before surgery achieves better perioperative glucose control with lower hypoglycemia risk compared to usual dosing 1, 2
• Continue insulin pump basal rates at 75-80% if patient uses a pump 1

Target Blood Glucose Range

Maintain blood glucose 100-180 mg/dL (5.6-10.0 mmol/L) within 4 hours of surgery and throughout the perioperative period 1, 2, 4

Critical Pitfall to Avoid

• Do NOT pursue stricter targets (<100 mg/dL or 80-180 mg/dL) as they do not improve outcomes and significantly increase hypoglycemia risk without benefit 1, 2, 4
• The 2021 guidelines suggested 80-180 mg/dL 1, but the most recent 2023 American Diabetes Association guidelines updated this to 100-180 mg/dL based on evidence showing tighter targets increase hypoglycemia without improving morbidity or mortality 1, 2

Monitoring Protocol

• Check blood glucose at least every 2-4 hours while patient is NPO (nothing by mouth) 1, 2, 4
• Administer short-acting (regular) or rapid-acting insulin (lispro, aspart, glulisine) as needed to maintain target range 1, 2
• Continue monitoring intraoperatively and postoperatively at the same frequency 1, 4

Management of Glucose Abnormalities

Hypoglycemia (<70 mg/dL)

• For glucose <60 mg/dL (3.3 mmol/L), administer glucose immediately even without symptoms 1
• If patient is conscious and able to swallow, give oral glucose (15-20g of fast-acting carbohydrates such as glucose tablets or hard candy) 1, 5
• If patient is unconscious or unable to swallow, administer intravenous glucose or intramuscular/subcutaneous glucagon 1 mg 1, 6
• Hypoglycemia risk peaks between midnight and 6:00 AM, requiring vigilant monitoring 1

Hyperglycemia (>180 mg/dL)

• Administer short- or rapid-acting insulin using correction doses 1, 2
• For glucose >300 mg/dL (16.5 mmol/L) in Type 1 diabetes or insulin-treated Type 2 diabetes, check for ketones to rule out diabetic ketoacidosis 1
• If ketones are present, call for urgent assistance and consider ICU transfer 1

Postoperative Management

Use basal-bolus insulin regimens (basal insulin plus premeal rapid-acting insulin) rather than correction-only insulin in noncardiac general surgery patients, as this approach improves glycemic outcomes and reduces perioperative complications 1, 2, 4

Critical Pitfall to Avoid

• Never use correction-only ("sliding scale") insulin without basal insulin coverage as this is associated with worse outcomes and higher complication rates 1, 2, 4

Resuming Home Medications

• Resume subcutaneous basal insulin 2-4 hours before stopping any IV insulin infusion to prevent rebound hyperglycemia 2
• Do not restart SGLT2 inhibitors until patient is clinically stable, has resumed normal diet, and capillary ketones are <0.6 mmol/L (typically 24-48 hours after surgery) 3
• Resume other oral medications when patient tolerates oral intake 1

Special Considerations

Glucocorticoid Use

• If patient receives perioperative steroids, anticipate substantial increases in insulin requirements (40-60% or more) in addition to basal insulin 1, 2
• For short-acting glucocorticoids (prednisone), give NPH insulin concomitantly as it peaks 4-6 hours after administration, matching steroid-induced hyperglycemia 1
• For long-acting glucocorticoids (dexamethasone), increase long-acting basal insulin doses 1

Preoperative Optimization

• For elective surgeries, target A1C <8% whenever possible to reduce surgical risk, mortality, and infection rates 1, 2, 4
• Some institutions have developed preoperative optimization programs that successfully lower perioperative glucose and reduce hypoglycemia 7