A 28-year-old man with insulin-dependent type 2 diabetes mellitus is scheduled for open appendicectomy under spinal anesthesia at 08:00 AM. He took his usual insulin dose (10 units of regular insulin) at 06:00 AM with a glass of milk. His blood glucose is 180 mg/dL on pre-operative assessment. He is anxious about fasting and asks if he can have breakfast. What is the most appropriate fasting advice for this patient?

Explanation

## Fasting Guidelines in Diabetic Patients **Key Point:** Diabetic patients undergoing surgery require special fasting and glycemic management. The standard approach is NPO from midnight with perioperative glucose-insulin-potassium (GIK) infusion to maintain euglycemia and prevent both hypoglycemia and hyperglycemia. ### Fasting in Diabetic Patients: Standard Protocol | Timing | Action | | --- | --- | | Night before surgery | NPO from midnight; withhold long-acting insulin | | Morning of surgery | Withhold short-acting insulin; check blood glucose | | Pre-operative | Establish IV access; start GIK infusion | | Intra-operative | Monitor glucose hourly; adjust infusion rate | | Post-operative | Resume oral intake and insulin when tolerating diet | **High-Yield:** The **GIK (Glucose-Insulin-Potassium) regimen** is the gold standard for perioperative glycemic control in diabetic patients: - Prevents hypoglycemia (from fasting + insulin) - Prevents hyperglycemia (from surgical stress) - Maintains cellular potassium homeostasis - Reduces post-operative complications ### Why NPO from Midnight? 1. **Aspiration risk:** Even diabetic patients must follow standard fasting guidelines (6 hours for solid food, 2 hours for clear fluids) 2. **Glycemic control:** Fasting baseline allows accurate perioperative glucose monitoring 3. **Insulin management:** Withholding morning insulin prevents hypoglycemia during fasting period 4. **Surgical safety:** Predictable gastric emptiness reduces perioperative morbidity **Clinical Pearl:** A patient who has already taken insulin (as in this case) and is fasting is at high risk for hypoglycemia. Immediate IV dextrose infusion is indicated if surgery is delayed. **Mnemonic: NPO-GIK** — **N**il **P**er **O**s, then **G**lucose-**I**nsulin-**K**alium infusion. ### Why Not Allow Breakfast? - **Aspiration risk:** Solid food requires 6 hours fasting; breakfast 2 hours before surgery violates this - **Glycemic unpredictability:** Oral intake + perioperative stress = difficult glucose control - **Insulin dosing:** Adjusting insulin for ad-hoc meals is unreliable and dangerous [cite:Barash Clinical Anesthesia 8e Ch 20; Harrison 21e Ch 467]