Anaesthetic Management of Insulinoma
The primary anaesthetic goal for insulinoma surgery is preventing intraoperative hypoglycemia through continuous glucose infusion while maintaining blood glucose levels above 60 mg/dL, with frequent monitoring to detect the dramatic glucose changes that occur during tumor manipulation and resection.
Preoperative Preparation
Glucose Assessment and Optimization
- Schedule surgery early in the day to minimize fasting time and reduce hypoglycemic risk 1
- Establish baseline glucose control and document any recent hypoglycemic episodes 2
- Ensure availability of rapid glucose measurement capabilities intraoperatively 3, 4
Equipment and Monitoring Setup
- Arrange for continuous or very frequent (every 15-30 minutes) blood glucose monitoring throughout the perioperative period 4, 2
- Consider continuous glucose monitoring systems if available, though these should not replace capillary blood glucose measurements during surgery 4
- Prepare glucose infusion pumps and concentrated glucose solutions (10-50%) for rapid administration 3, 4
Intraoperative Management
Glucose Control Strategy
- Initiate continuous 10% glucose infusion immediately after induction to prevent hypoglycemia until tumor resection 4
- Maintain plasma glucose levels above 60 mg/dL as the critical threshold to prevent symptomatic hypoglycemia 2
- Target glucose range of 60-150 mg/dL during tumor manipulation phase 4
Critical Monitoring Points
- Monitor glucose every 15-30 minutes or continuously, as hypoglycemia symptoms remain masked under general anesthesia 2
- Expect severe hypoglycemia during tumor palpation and manipulation due to mechanical stimulation causing insulin release 5, 6
- Watch for dramatic increases in glucose requirements (increased infusion rates) when the tumor is handled 5
Anaesthetic Technique
- Propofol-based general anaesthesia combined with epidural analgesia (T9/10 level) is effective and well-tolerated 3
- Use fentanyl (200 mcg) for induction analgesia and vecuronium (6 mg) for neuromuscular blockade 3
- Maintain anaesthesia with continuous propofol infusion and epidural analgesia 3
Tumor Localization Support
- Rapid immunoreactive insulin (IRI) measurements can help confirm tumor localization during surgical exploration 3
- Glucose infusion rate changes may indicate tumor manipulation before glucose levels change 5, 6
Postoperative Management
Immediate Post-Resection Period
- Anticipate rapid hyperglycemia immediately after tumor removal (within 4 minutes) as insulin levels drop precipitously 5
- Discontinue or dramatically reduce glucose infusion as soon as tumor is excised 3, 6
- Consider insulin infusion if glucose rises above 180-200 mg/dL to prevent rebound hyperglycemia 4
Recovery Phase Monitoring
- Continue hourly glucose monitoring for at least 24-48 hours postoperatively 4, 2
- Target glucose range of 100-180 mg/dL in the immediate postoperative period 4
- Verify successful tumor removal by documenting reduced IRI levels and stable glucose without continuous infusion 3, 6
Critical Pitfalls to Avoid
Hypoglycemia Management
- Never rely on clinical signs alone to detect hypoglycemia, as general anaesthesia masks all symptoms (tremor, diaphoresis, tachycardia) 2
- Do not wait for symptomatic hypoglycemia before starting glucose infusion—begin prophylactically at induction 4, 2
Glucose Infusion Errors
- Avoid prophylactic massive glucose infusions without monitoring, as this can cause severe rebound hyperglycemia post-resection 6
- Do not abruptly stop glucose infusion during tumor manipulation, even if glucose levels appear adequate 5
Monitoring Gaps
- Continuous glucose monitors show interstitial glucose with a lag time and may be inaccurate during hemodynamic changes—always confirm with capillary blood glucose 1
- Glucose levels can change within minutes during tumor handling—30-minute monitoring intervals may be insufficient 5