What is the appropriate intra‑operative insulin regimen (continuous IV regular insulin dose, glucose targets, monitoring, dextrose supplementation, and postoperative transition) for a diabetic patient undergoing surgery?

Intraoperative Insulin Management for Diabetic Patients Undergoing Surgery

Glucose Targets During Surgery

Target intraoperative blood glucose between 140–180 mg/dL (7.7–10 mmol/L) to minimize morbidity and mortality while avoiding hypoglycemia. 1

• Hyperglycemia >180 mg/dL (10 mmol/L) increases perioperative morbidity, particularly infections and mortality 1
• Tight glycemic control targeting 80–120 mg/dL (4.4–6.7 mmol/L) increases severe hypoglycemia rates and possibly mortality 1
• A broader target of 90–180 mg/dL (5–10 mmol/L) is practical and safe, avoiding hypoglycemia while maintaining glucose <180 mg/dL 1
• For cardiac surgery specifically, target postoperative glucose ≤180 mg/dL reduces deep sternal wound infection without increasing hypoglycemia 1

Continuous IV Insulin Infusion Protocol

Use continuous intravenous regular insulin infusion (IVES) for all diabetic patients requiring insulin during surgery, always combined with IV glucose (4 g/h equivalent) and electrolyte monitoring. 1

Starting Insulin Infusion Rates

• Initial rate: 0.5–1.0 units/hour for most patients, adjusted based on blood glucose 1, 2
• Type 1 diabetes: Start at 1 unit/hour 1
• Type 2 diabetes: Start at 2 units/hour 1
• Stress hyperglycemia (no prior diabetes diagnosis): Start at lower rates, 0.5 units/hour 1

Insulin Titration Algorithm

Blood Glucose (mg/dL)	Blood Glucose (mmol/L)	Action
<80	<4.4	Stop insulin; give 30% glucose 2 ampules (6g); recheck in 15-30 min [1]
80-140	4.4-7.7	Decrease infusion rate by 0.5-1 unit/hour [1]
140-180	7.7-10	Maintain current rate [1]
180-250	10-13.9	Increase by 1 unit/hour [1]
>250	>13.9	Increase by 2 units/hour; consider bolus 2-4 units [1]

• Adjust insulin infusion rate every 1–2 hours based on blood glucose trends 1
• For glucose >300 mg/dL (16.5 mmol/L), give IV bolus of 3–5 units regular insulin, then increase infusion rate 1

Mandatory Dextrose Supplementation

Always administer IV glucose (dextrose) concurrently with insulin infusion at approximately 4 g/hour (equivalent to D10% at 40 mL/hour) to prevent hypoglycemia. 1

• Use D5W or D10W solutions depending on fluid requirements 1
• Adjust dextrose rate if hypoglycemia occurs despite stopping insulin 1
• Continue dextrose infusion even when insulin is temporarily held for low glucose 1

Blood Glucose Monitoring Frequency

Measure blood glucose every 1–2 hours during surgery and the immediate postoperative period using arterial or venous blood samples, not capillary measurements. 1

• Capillary glucose measurements overestimate blood glucose, especially with vasoconstriction and hypoglycemia 1
• A capillary reading of 70 mg/dL (3.8 mmol/L) should be considered hypoglycemia and verified by laboratory measurement 1
• Use arterial or venous blood samples from the opposite side of glucose infusion 1
• Increase monitoring to every 15–30 minutes after correcting hypoglycemia until glucose stabilizes 1

Electrolyte Monitoring

Check serum potassium every 4 hours during insulin infusion, targeting 4.0–4.5 mmol/L, as insulin drives potassium intracellularly. 1

• Insulin-induced hypokalemia is a significant risk during IV infusion 1
• Supplement potassium as needed to maintain levels >4.0 mmol/L 1

Insulin Pump Management

If the patient uses a personal insulin pump, remove it immediately at the start of surgery and transition to IVES insulin infusion. 1

• Do not allow pump continuation during surgery due to inability to monitor and adjust 1
• Mandatory immediate follow-on with IVES insulin when pump is removed 1

Transition from IV to Subcutaneous Insulin Postoperatively

Administer the first dose of subcutaneous basal insulin (glargine or detemir) 2–4 hours before stopping the IV insulin infusion to prevent rebound hyperglycemia. 3, 4, 5

Calculating Subcutaneous Insulin Dose

• Total daily subcutaneous dose = 50% of the total 24-hour IV insulin infused 3, 6
• Basal insulin (glargine/detemir) = 50% of total subcutaneous dose (given once daily at 20:00 hours) 3, 6
• Prandial insulin (lispro/aspart/glulisine) = 50% of total subcutaneous dose divided among three meals 3, 6

Example Calculation

• If patient received 48 units IV insulin over 24 hours:
  • Total subcutaneous dose = 24 units (50% of 48)
  • Basal insulin = 12 units glargine once daily
  • Prandial insulin = 12 units total (4 units before each meal)

Timing of Transition

• Give first basal insulin dose 2–4 hours before stopping IV infusion 3, 4
• Continue IV insulin for 1–2 hours after subcutaneous basal dose to ensure adequate overlap 3
• Stop IV insulin only when infusion rate is ≤0.5 units/hour 3
• If IV rate is ≥5 units/hour, this indicates major insulin resistance requiring continued IV therapy 3

Hypoglycemia Management

Treat any blood glucose <70 mg/dL (3.8 mmol/L) immediately, even without symptoms. 1, 7

• Stop insulin infusion immediately 1, 7
• Give 30% glucose 2 ampules (6 g) IV or 15–20 g dextrose (100–150 mL D10% or 20–30 mL D50%) 1, 7
• Recheck glucose in 15 minutes and repeat dextrose if needed 1, 7
• Resume insulin at reduced rate (50% of previous) when glucose >100 mg/dL 1
• Never give oral glucose to unconscious or sedated patients due to aspiration risk 7

Perioperative Basal Insulin Adjustment for Patients on Home Insulin

Reduce the patient's usual basal insulin dose by approximately 25% the evening before surgery to achieve target glucose with decreased hypoglycemia risk. 8

• For long-acting analogs (glargine/detemir), give 75–80% of usual dose 8, 7
• For NPH insulin, give 50% of usual morning dose 8, 7
• Continue basal insulin even when NPO to prevent ketoacidosis in type 1 diabetes 7

Special Considerations

Type 1 Diabetes

• Never completely withhold insulin, even when NPO, to prevent diabetic ketoacidosis 1, 7
• Higher insulin requirements expected (typically 1 unit/hour or more) 1
• More aggressive monitoring required due to absolute insulin deficiency 1

Type 2 Diabetes

• Lower starting insulin rates (0.5–2 units/hour) usually sufficient 1, 9
• May have higher insulin resistance requiring higher infusion rates 1

Cardiac Surgery

• Target postoperative glucose <180 mg/dL reduces deep sternal wound infection 1
• Intensive intraoperative control (<140 mg/dL) has uncertain effectiveness and may increase stroke risk 1
• Continue IV insulin until morning of postoperative day 3 for optimal outcomes 1

Emergency Surgery

• Start IV insulin immediately if glucose >180 mg/dL 1
• Do not delay surgery to optimize glucose control 1
• Manage glucose intraoperatively with continuous infusion 1

Common Pitfalls to Avoid

• Never use sliding-scale insulin alone without basal insulin coverage during surgery—this reactive approach is condemned by all major guidelines 4, 5
• Never stop IV insulin abruptly without overlapping subcutaneous basal insulin, as this causes dangerous rebound hyperglycemia and potential ketoacidosis 3, 4
• Never rely on capillary glucose measurements during surgery, as they overestimate values and are unreliable with vasoconstriction 1
• Never give insulin without concurrent dextrose infusion, as this dramatically increases hypoglycemia risk 1
• Never target tight glycemic control (80–110 mg/dL) intraoperatively, as this increases severe hypoglycemia and mortality without benefit 1
• Do not use premixed insulin (70/30) in the perioperative period due to unacceptably high hypoglycemia rates 8

Postoperative Glucose Monitoring

Continue glucose monitoring every 2–4 hours postoperatively until the patient is stable on subcutaneous insulin and eating regular meals. 7, 3, 4

• Check glucose before each meal and at bedtime once eating 7, 3
• Target postoperative glucose 140–180 mg/dL for non-critically ill patients 7, 4, 5
• Adjust subcutaneous insulin doses daily based on glucose patterns 7, 3