Intraoperative Blood Sugar Management
Target intraoperative blood glucose between 140-180 mg/dL (7.7-10 mmol/L) using continuous intravenous insulin infusion, with hourly monitoring to avoid both hyperglycemia above 180 mg/dL and the risks of overly tight control below 140 mg/dL. 1
Target Blood Glucose Range
The most recent ERAS Society guidelines (2023) provide the clearest recommendation: maintain glucose between 140-180 mg/dL (7.7-10 mmol/L) during surgery using a variable rate insulin infusion 1. This target applies to both diabetic and non-diabetic patients experiencing stress hyperglycemia 1.
Why Not Tighter Control?
Extremely tight intraoperative glucose control (<140 mg/dL) is not recommended based on high-quality evidence from cardiac surgery 1. The ACC/AHA guidelines cite a Mayo Clinic randomized trial of 400 patients where intensive treatment (targeting very tight control) actually caused increased incidence of death and stroke compared to conventional treatment 1. A Cleveland Clinic retrospective analysis of 4,300 cardiac surgery patients found that glucose concentrations <140 mg/dL were not associated with improved outcomes compared to moderate hyperglycemia, despite infrequent hypoglycemia 1.
Upper Limit Threshold
Blood glucose ≥180-200 mg/dL is associated with worse outcomes including increased mortality, complications, and infections 1. Hyperglycemia impairs neutrophil function, causes overproduction of reactive oxygen species and inflammatory mediators, and contributes to direct cellular damage and vascular dysfunction 1.
Insulin Administration Method
Use continuous intravenous insulin infusion as the preferred method for intraoperative glucose management 1, 2. The variable rate insulin infusion is most appropriate intraoperatively, particularly in emergency laparotomy patients who frequently have fluid shifts and acidosis 1.
Why IV Insulin?
The short half-life of IV insulin (<15 minutes) allows flexibility in adjusting the infusion rate with unpredicted changes in nutrition or patient health status 1. Subcutaneous insulin should be avoided in critically ill patients, particularly during hypotension or shock 1.
Monitoring Frequency
Measure point-of-care blood glucose at minimum every hour while on insulin infusion until serum glucose levels are stable 1. More frequent monitoring every 1-2 hours may be appropriate for patients with greater glycemic variability 3.
Common Pitfall
Compliance with hourly glucose measurements decreases with increasing length of procedure, dropping to only 72.5% in one academic center study 4. Set explicit reminders or protocols to maintain hourly monitoring throughout the entire surgical case, regardless of duration.
Initiation Threshold
Start insulin infusion when blood glucose exceeds 180 mg/dL 1, 2. The Society of Thoracic Surgeons recommends that patients with or without diabetes who have persistently elevated glucose >180 mg/dL during the perioperative period should receive IV insulin infusions 1.
Special Populations
Cardiac Surgery Patients
For cardiac surgery specifically, maintain target glucose <180 mg/dL with continuous IV insulin during surgery and until the morning of the third postoperative day 1. The Portland Diabetes Project demonstrated that continuous IV insulin to maintain glucose 120-160 mg/dL resulted in reduced incidence of deep sternal wound infection 1.
Emergency Surgery Patients
Emergency laparotomy patients require the same 140-180 mg/dL target range 1. These patients are at particularly high risk due to physiological stress response causing insulin resistance, which serves as an indirect marker of tissue injury 1.
Critical Warnings
Avoid Overly Aggressive Treatment
Do not target glucose <100-140 mg/dL intraoperatively 1, 2. Stricter glycemic targets increase the risk of hypoglycemia without improving outcomes and may actually increase mortality 1, 2. The evidence shows that attempting extremely tight control can cause harm, particularly increased stroke risk 1.
Recognize Hypoglycemia Risk
Hypoglycemic incidents (<60 mg/dL) occur in approximately 0.1% of measurements even with moderate targets 4. Elderly patients and those with renal insufficiency are at increased risk due to decreased renal gluconeogenesis, impaired counterregulatory responses, and decreased insulin degradation 1.
Preoperative Optimization
Optimize glucose control before surgery, targeting <180 mg/dL with continuous IV insulin 1. Measuring preoperative hemoglobin A1c may help assess adequacy of glycemic control and identify patients at risk for postoperative hyperglycemia 1. The American Diabetes Association recommends A1C target <8% for elective surgeries whenever possible 2.
Documentation and Compliance
Real-world data shows that compliance with correct insulin adjustments is only 12.4%, with providers under-dosing insulin by an average of 0.85 U/h compared to protocol 4. This results in glucose levels within target range only 28% of the time, with hyperglycemic incidents (>180 mg/dL) occurring 28% of the time 4. Implement structured protocols with clear decision algorithms to improve adherence.