Do I need to start a type 1 diabetic patient on variable rate insulin (VRI) when requiring fasting for surgery?

Perioperative Management of Type 1 Diabetic Patients Requiring Fasting for Surgery

For type 1 diabetic patients requiring fasting for surgery, variable rate insulin infusion (VRII) is not necessary if only one meal will be missed, but should be initiated for longer fasting periods or complex surgeries. 1

Decision Algorithm for VRII Use

Minor Surgery (One Meal Missed)

• Continue insulin pump therapy or usual subcutaneous insulin regimen
• For patients on insulin pumps:
  • Maintain basal insulin infusion during fasting and surgery
  • Some protocols recommend reducing to 80% of usual basal rate during surgery 1
  • Ensure pump site is distant from surgical field and accessible to anesthetist
  • Target blood glucose: 6-10 mmol/L (acceptable range 4-12 mmol/L) 1

Major Surgery or Multiple Meals Missed

• Start variable rate intravenous insulin infusion (VRII)
• Remove insulin pump if present, starting VRII at least 30 minutes before pump removal 1
• Use ultra-rapid short-acting insulin analogues administered continuously via electronic syringe pump 1
• Always administer with IV glucose (equivalent of 4g/h) and monitor electrolytes 1

Monitoring Requirements

• Check capillary blood glucose hourly during surgery and in recovery 1
• Use arterial or venous blood samples rather than capillary measurements when possible 1
• Monitor potassium every 4 hours while on insulin infusion 1

Insulin Infusion Rate Guidance

For blood glucose levels:

• 5-7 mmol/L: 0.5 IU/h
• 7-9 mmol/L: 1 IU/h
• 9-11 mmol/L: 1.5 IU/h
• 11-14 mmol/L: 2 IU/h
• 14-17 mmol/L: 3 IU/h + 4 IU bolus 2

Transition Back to Usual Insulin Regimen

• For insulin pump users: Reconnect pump and run basal rate for at least 2 hours before stopping IV insulin 1
• For non-pump users: Transition to subcutaneous insulin when patient is stable and eating 1

Common Pitfalls and Caveats

1. Insulin deficiency risk: Type 1 diabetics become insulin deficient within an hour of pump disconnection, requiring immediate IV insulin 1
2. Hypoglycemia management: For blood glucose <4 mmol/L, stop insulin infusion immediately and administer IV glucose 2
3. Equipment considerations: Some imaging procedures (MRI, CT) require pump removal; plan accordingly 1
4. Surgical timing: Schedule diabetic patients early in the morning to minimize fasting time 1

Special Considerations

• Ensure patients bring adequate supplies of pump equipment if continuing pump therapy 1
• Different anesthetic regimens may affect glucose homeostasis through effects on counter-regulatory hormones 1
• Minor changes in blood glucose during surgery are expected and not an indication to stop insulin pump therapy 1

The Joint British Diabetes Society guidelines provide clear direction that patients missing only one meal can safely continue their usual insulin regimen, while those requiring longer fasting periods benefit from VRII to maintain optimal glycemic control and reduce perioperative complications 1.