What are the insulin instructions for a patient who stopped oral medication the previous day morning and underwent surgery the next day at 2 pm?

Postoperative Insulin Management for Diabetic Patient After Surgery

Immediate Postoperative Insulin Protocol

Continue intravenous insulin infusion until blood glucose stabilizes at ≤180 mg/dL (10 mmol/L) and the patient resumes oral feeding, then transition to subcutaneous basal-bolus insulin regimen. 1

IV Insulin Management (Immediate Post-Op Period)

• Maintain IV insulin infusion targeting blood glucose between 100-180 mg/dL (5.6-10.0 mmol/L) 1
• Monitor capillary blood glucose every 1-2 hours while NPO to detect glycemic excursions 1
• Administer glucose immediately if blood glucose drops <60 mg/dL (3.3 mmol/L), even without symptoms 1
• Continue IV insulin until blood glucose remains stable for at least 24 hours 1, 2

Transition from IV to Subcutaneous Insulin

Administer subcutaneous long-acting insulin (glargine/Lantus) 2 hours before discontinuing the IV insulin infusion to prevent rebound hyperglycemia. 2

Calculating Basal Insulin Dose

• Calculate the total IV insulin administered over the last 24 hours when glucose was stable 3, 2
• Basal insulin dose = 50% of the total 24-hour IV insulin requirement, given as once-daily glargine 3, 2
• Administer this dose 2 hours before stopping the IV infusion due to glargine's 1-hour onset of action 2

Calculating Prandial Insulin Dose

• Prandial insulin = the remaining 50% of 24-hour IV insulin, divided by 3 meals 3, 1
• Use ultra-rapid insulin analogue (glulisine, lispro, or aspart) before each meal 3, 1
• Administer immediately before meals, or after meals if oral intake is uncertain 2
• Give half the planned prandial dose if caloric intake is insufficient 3

Example Calculation

If the patient received 48 units of IV insulin in the last 24 hours:

• Basal insulin (glargine): 24 units once daily (given 2 hours before stopping IV)
• Prandial insulin (ultra-rapid): 8 units before each meal (24 units ÷ 3 meals)

Correction Dose Protocol for Hyperglycemia

For pre-meal blood glucose >300 mg/dL (16.5 mmol/L), check for ketosis and administer 6 units of ultra-rapid insulin subcutaneously. 3

Hyperglycemia Management Algorithm

• If ketonuria = 0 or ketonemia <0.5 mmol/L: Give 6 units ultra-rapid insulin SC, recheck glucose in 3 hours 3
• If ketonuria 1+ or ketonemia 0.5-1.5 mmol/L: Give 6 units ultra-rapid insulin SC, recheck glucose and ketones in 3 hours 3
• If ketonuria 2+ or ketonemia >1.5 mmol/L: Transfer to ICU for IV insulin infusion 3

Critical Pitfalls to Avoid

Never discontinue IV insulin before administering subcutaneous basal insulin, as this creates a dangerous gap in insulin coverage that can precipitate diabetic ketoacidosis, especially in type 1 diabetes patients. 2

• The 2-hour overlap is mandatory because glargine has no peak effect and requires time to establish steady-state coverage 2
• Type 1 diabetes patients require continuous basal insulin even when NPO to prevent ketoacidosis 2
• Avoid using sliding-scale insulin alone without basal insulin, as this approach is ineffective and increases complications 4, 5

Ongoing Monitoring Requirements

• Check capillary blood glucose before each meal and at bedtime 1
• Adjust insulin doses daily based on glucose patterns and carbohydrate intake 1
• Ensure adequate hydration for severe hyperglycemia 3
• The basal-bolus regimen reduces postoperative complications by 66% compared to sliding-scale insulin alone (24.3% vs 8.6% complication rate) 5

Discharge Planning Considerations

• Continue the basal-bolus regimen established in hospital at discharge 3
• For patients with HbA1c <8%, arrange follow-up with primary physician within one month 3
• For HbA1c >9% or unstable glucose levels >200 mg/dL (11 mmol/L), request diabetologist consultation before discharge 3