What are the anesthesia considerations for patients with insulin-dependent diabetes undergoing surgery?

Anesthesia Considerations for Insulin-Dependent Diabetes

For patients with insulin-dependent diabetes undergoing surgery, maintain perioperative blood glucose between 6-10 mmol/L (100-180 mg/dL), schedule surgery first on the list to minimize fasting, and continue insulin pump therapy at 80% basal rate for minor procedures, or switch to IV insulin infusion for major surgery. 1, 2, 3

Preoperative Assessment

Glycemic Control Evaluation

• Measure HbA1c preoperatively with target <8% for elective surgery 2, 3
• Postpone elective surgery if HbA1c >8% or blood glucose >16.5 mmol/L (297 mg/dL) on surgery day, referring to diabetology for optimization 3
• Screen for recent hypoglycemic episodes in the past week, as these predict perioperative risk 2
• Assess for hypoglycemia unawareness, present in 40% of type 1 diabetes patients, requiring more vigilant monitoring 2

Complication Screening

• Evaluate for gastroparesis through questioning about abdominal pain, bloating, and vomiting, as this creates aspiration risk requiring rapid sequence induction 2
• Screen for silent myocardial ischemia (present in 30-50% of diabetic patients) through ECG and consider stress testing if major surgery planned 2
• Assess for cardiac autonomic neuropathy through orthostatic blood pressure changes and heart rate variability, as this increases sudden death risk 2, 3
• Measure glomerular filtration rate as diabetic nephropathy increases acute renal failure risk 2

Medication Management

• Hold metformin on the day of surgery due to lactic acidosis risk, particularly with renal impairment 2, 3
• Discontinue SGLT2 inhibitors 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis 3

Insulin Pump Management (For Pump Users)

Preoperative Preparation

• Verify basal rate accuracy before surgery through fasting assessment 1
• Position infusion site distant from surgical field, away from diathermy area, and readily accessible to anesthesiologist 1
• For procedures requiring imaging (CT/MRI), remove pump and metal infusion set; for X-rays, remove pump from field 1
• Advise patient to bring adequate supply of equipment and spares for entire hospital admission 1

Intraoperative Pump Management

• For minor surgery (only one meal missed), continue pump at 80% basal rate during fasting and surgery 1
• The Joint British Diabetes Societies recommend patients can remain on continuous subcutaneous insulin infusion (CSII) if only one meal is missed 1
• If pump must be disconnected, start IV insulin immediately—patients become insulin deficient within one hour 1, 3
• Calculate IV insulin rate from total basal rate available in pump menu, typically starting at hourly basal rate and titrating to blood glucose 1

Critical Pump Pitfall

• Never stop insulin pumps without immediate IV insulin replacement in type 1 diabetes, as ketoacidosis develops within hours 2, 3
• If disconnecting pump, leave it running but detached from insertion cannula, then immediately start IV insulin 1

Intraoperative Glycemic Management

Target Blood Glucose

• Maintain blood glucose 6-10 mmol/L (100-180 mg/dL) intraoperatively 1, 2, 3
• Acceptable range is 4-12 mmol/L per Joint British Diabetes Societies 1
• Hyperglycemia >10 mmol/L (180 mg/dL) increases morbidity and mortality, particularly from infection 2
• Hyperglycemia >13.5 mmol/L (250 mg/dL) carries 10-fold higher complication risk 2

Insulin Administration for Non-Pump Patients

• Use continuous IV insulin infusion via electronic syringe for insulin-dependent patients or those with stress hyperglycemia 2, 3
• Basal-bolus insulin regimen (glargine once daily plus rapid-acting before meals) is superior to sliding scale insulin, reducing complications from 24.3% to 8.6% 4
• For patients on basal insulin (glargine), reduce evening dose before surgery to 60-87% (optimal ~75%) of usual dose to achieve target range with lower hypoglycemia risk 3, 5

Glucose Monitoring

• Monitor capillary blood glucose hourly during surgery 1, 2
• Do not use continuous glucose monitor (CGM) readings for intraoperative management due to lag time and perfusion-dependent inaccuracy during anesthesia 1, 2
• Minor blood glucose changes during surgery are expected and not an indication to stop insulin pump 1

Anesthetic Technique Considerations

• Prioritize regional anesthesia when possible for superior postoperative pain control and reduced insulin resistance 2
• Different anesthetic regimens affect glucose homeostasis through counter-regulatory hormones, sympathetic nervous system, and hypothalamic-pituitary-adrenal axis 1

Surgical Scheduling Strategy

• Schedule diabetic patients first on the list to minimize fasting time 1, 6
• Ensure insulin management plans are available in advance 1

Postoperative Management

Glucose Monitoring and Targets

• Continue hourly capillary blood glucose monitoring until patient is fully conscious and capable of self-management 1, 2, 3
• Maintain same target range of 6-10 mmol/L (100-180 mg/dL) 2, 3
• Patients should continue increased monitoring frequency for 1-2 days after surgery 1

Insulin Management

• For pump users, resume basal infusion once patient can manage device and is eating 1, 2, 3
• Start bolus insulin dosing with first postoperative carbohydrate ingestion 1, 2
• When transitioning from IV to pump, connect pump and infuse basal rate for at least 30 minutes before discontinuing IV insulin 1
• Maintain glucose infusion (10% dextrose at 40 mL/h) for insulin-dependent patients to prevent recurrent hypoglycemia 2

Managing Postoperative Hyperglycemia

• If blood glucose increases postoperatively in alert pump users, use pump's bolus calculator to determine correction dose 1
• Significant hyperglycemia may reflect pump failure, disconnection, or physiological stress response to surgery 1
• Apply "sick day rules" algorithms for unexplained high blood glucose 1

Critical Pitfalls to Avoid

Hypoglycemia Prevention

• Do not aim for strict normoglycemia (tighter than 5.6-10 mmol/L), as this increases hypoglycemia without improving outcomes 2, 3, 7
• Treat hypoglycemia <4 mmol/L (<70 mg/dL) per protocol with IV glucose if required 1
• Group receiving 100% of usual basal insulin dose had highest hypoglycemia rate compared to 60-87% dosing 5

Hyperglycemia Management

• If blood glucose >14 mmol/L, check pump and infusion set, test for ketones 1
• For uncontrolled hyperglycemia perioperatively, disconnect pump and immediately start variable rate IV insulin infusion 1

Monitoring Considerations

• Check potassium levels every 4 hours in patients receiving insulin therapy to prevent life-threatening hypokalemia 6
• Recognize that subcutaneous insulin absorption depends on adequate tissue perfusion and blood pressure maintenance during surgery 1

Evidence Quality Note

The British Journal of Anaesthesia guidelines 1 provide the most comprehensive framework for pump management, while the American Diabetes Association recommendations 2, 3 establish broader perioperative glycemic targets. The RABBIT 2 surgery trial 4 provides the strongest evidence (RCT) that basal-bolus insulin reduces complications compared to sliding scale, though this applies primarily to non-pump users.