Preoperative Blood Glucose Target
For both diabetic and non-diabetic patients undergoing surgery, target a blood glucose range of 100–180 mg/dL (5.6–10.0 mmol/L) in the perioperative period, measured within 4 hours of surgery. 1
Target Ranges by Patient Population
Diabetic Patients
- Preoperative HbA1c goal: <8% (<63.9 mmol/mol) for elective surgeries whenever possible 1, 2
- Blood glucose target: 100–180 mg/dL (5.6–10.0 mmol/L) in the perioperative period 1, 2, 3
- If achieving HbA1c <8% is not feasible before elective surgery, still target the 100–180 mg/dL glucose range preoperatively 2
- Some institutions implement preoperative optimization programs to lower HbA1c before elective procedures, which can improve surgical outcomes 1
Non-Diabetic Patients
- Same target range: 100–180 mg/dL (5.6–10.0 mmol/L) 1, 3
- Preoperative hyperglycemia (even moderate elevations of 100–139 mg/dL) in patients without known diabetes is associated with significantly higher postoperative infection rates and may indicate unrecognized prediabetes or diabetes 4
- Approximately 15% of patients with preoperative glucose ≥100 mg/dL are diagnosed with diabetes within one year after surgery 4
Why Not Tighter Control?
Avoid stricter glycemic targets below 80 mg/dL or tighter ranges like 80–110 mg/dL. 1, 5
- Perioperative glycemic goals stricter than 80–180 mg/dL do not improve outcomes and are associated with significantly more hypoglycemia 1, 5
- Multiple studies demonstrate no mortality benefit from tighter control, with increased hypoglycemic events (56–80% reduction in hypoglycemia with less strict targets) 6, 7, 3
- The broader 100–180 mg/dL range balances prevention of hyperglycemia-related complications (infections, cardiovascular events, wound healing issues) against hypoglycemia risk 3
Monitoring Frequency
- Check blood glucose at least every 2–4 hours while the patient is NPO (nothing by mouth) 1, 5, 3
- Continue frequent monitoring throughout the perioperative period 3
- Do not use continuous glucose monitoring (CGM) devices alone for intraoperative glucose assessment; confirm with point-of-care testing 1, 3
Medication Management on Day of Surgery
Hold These Medications:
- Metformin: Withhold on the day of surgery 1, 6, 7, 1, 5
- SGLT2 inhibitors: Discontinue 3–4 days before surgery to prevent euglycemic ketoacidosis 1, 5, 3
- All other oral glucose-lowering agents: Hold the morning of surgery 1, 6, 7, 1, 5
Insulin Adjustments:
- Basal insulin: Give 75–80% of usual long-acting analog dose (or 50% of NPH dose) the evening before surgery 1, 5, 3
- A 25% reduction in basal insulin the night before surgery achieves perioperative glucose goals with lower hypoglycemia risk compared to usual dosing 1, 5
- Short- or rapid-acting insulin: Use as needed for correctional coverage when glucose exceeds target range 1, 5
Uncertain Medications:
- GLP-1 receptor agonists: Limited data on safe perioperative use and potential effects on delayed gastric emptying 1
Postoperative Insulin Strategy
Use basal-bolus insulin regimens (basal insulin plus scheduled prandial doses) rather than correction-only sliding scale insulin. 1, 5, 3
- In noncardiac general surgery patients, basal-bolus coverage is associated with improved glycemic outcomes and lower rates of perioperative complications compared to reactive sliding scale alone 1, 6, 1, 3
- Correction-only insulin without basal coverage results in poorer glycemic control and higher complication rates 3
Common Pitfalls to Avoid
- Do not skip preoperative glucose measurement: In one study, 24.9% of diabetic surgical patients had no recorded glucose values before or after surgery 8
- Do not continue usual insulin doses unchanged: This increases hypoglycemia risk during the fasting perioperative period 1, 5
- Do not rely on HbA1c alone: Recent glycemic variability (hyper- or hypoglycemia) affects perioperative management even with adequate HbA1c 9
- Do not forget to assess for hypoglycemia history: Prior hypoglycemic episodes increase risk of subsequent events, particularly between midnight and 6:00 AM 5