How to manage diabetes in a patient with diabetes undergoing herniorrhaphy (hernia repair) before and after surgery, particularly when the patient is NPO (nil per os, nothing by mouth)?

Perioperative Diabetes Management for Herniorrhaphy

Direct Recommendation

For a diabetic patient undergoing herniorrhaphy, hold metformin on the day of surgery, discontinue SGLT2 inhibitors 3-4 days prior, reduce long-acting insulin to 75-80% (or NPH to 50%) the morning of surgery, maintain blood glucose between 100-180 mg/dL throughout the perioperative period, and monitor glucose every 2-4 hours while NPO with IV insulin plus glucose (4g/hour) as needed. 1

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Preoperative Management

Scheduling and Fasting

• Schedule the patient as the first case of the morning to minimize fasting duration and reduce glycemic disruption 1, 2
• Avoid prolonged fasting periods, as this increases risk of both hypoglycemia and stress-induced hyperglycemia 1

Preoperative Assessment

• Target HbA1c <8% for elective herniorrhaphy whenever possible 1, 2
• If HbA1c >8%, consider delaying surgery for optimization to reduce surgical complications 2
• Measure preoperative blood glucose with target range 100-180 mg/dL within 4 hours of surgery 1

Medication Adjustments (Day Before and Day of Surgery)

Oral Medications:

• Hold metformin on the day of surgery 1, 2
• Discontinue SGLT2 inhibitors 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis 1, 2
• Hold all other oral glucose-lowering agents the morning of surgery 1

Insulin Adjustments:

• Give 75-80% of long-acting analog insulin (e.g., glargine, detemir) the morning of surgery 1
• Give 50% of NPH insulin dose if using intermediate-acting insulin 1
• A 25% reduction of basal insulin the evening before surgery is associated with better perioperative glucose control and lower hypoglycemia risk 1
• For insulin pump users, maintain the pump until arrival in the surgical unit 3

Critical Pitfall: GLP-1 receptor agonists have limited safety data regarding delayed gastric emptying in the perioperative period; use clinical judgment for timing of discontinuation 1

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Intraoperative Management (While NPO)

Glucose Monitoring

• Monitor blood glucose every 2-4 hours while the patient is NPO 1
• Use arterial or venous blood samples rather than capillary measurements when possible, as capillary readings overestimate glucose levels, especially with vasoconstriction 1, 3
• Target glucose range: 100-180 mg/dL (5.6-10.0 mmol/L) 1
• Do not use CGM alone for glucose monitoring during surgery 1

Insulin Administration While NPO

• Use IV insulin infusion (short- or rapid-acting) for patients requiring insulin while NPO 1
• Always administer IV insulin with IV glucose (equivalent of 4g/hour) and electrolytes 1
• Ultra-rapid short-acting analogs administered continuously are preferred 1, 2
• Dose with short- or rapid-acting insulin as needed based on glucose readings 1

Electrolyte Management

• Monitor potassium every 4 hours in patients receiving insulin therapy to prevent life-threatening insulin-induced hypokalemia 1, 2
• Target potassium 4-4.5 mmol/L 2
• All IV solutions may be used perioperatively, including Ringer lactate 1

Critical Pitfall: Stricter glycemic goals (<80 mg/dL) are not advised, as they increase hypoglycemia risk without improving outcomes 1

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Postoperative Management

Transition from IV to Subcutaneous Insulin

• Maintain IV insulin until stable blood glucose <180 mg/dL is achieved 1
• Stop IV insulin at resumption of oral feeding 1
• If hourly insulin requirement is ≤0.5 IU/hour, stop the infusion; if ≥5 IU/hour, this indicates major insulin resistance requiring continued IV therapy 1

Transition Protocol:

• Administer long-acting (basal) insulin immediately after stopping IV insulin, ideally at 20:00 hours 1
• Give ultra-rapid analog insulin with the first meal, adjusted to carbohydrate intake 1
• For patients not previously on insulin requiring continued therapy postoperatively, start at 0.5-1 IU/kg (half basal, half rapid-acting) 1

Glucose Monitoring Postoperatively

• Continue monitoring blood glucose every 2-4 hours initially 1
• Any unexplained malaise should be considered hypoglycemia until proven otherwise 3

Hypoglycemia Management

• Treat glucose <60 mg/dL (3.3 mmol/L) immediately, even without symptoms 1
• For glucose 70-100 mg/dL (3.8-5.5 mmol/L) with symptoms, administer glucose 1
• Prefer oral glucose when patient is conscious; use IV glucose if unconscious or unable to swallow 1

Hyperglycemia Management

• For glucose >297 mg/dL (16.5 mmol/L) in Type 1 diabetes or insulin-treated Type 2 diabetes, check for ketosis immediately 1, 2
• If ketosis present, suspect diabetic ketoacidosis and initiate ultra-rapid insulin with consideration for ICU transfer 1
• In Type 2 diabetes, severe hyperglycemia may indicate hyperosmolar state (>320 mosmol/L); measure electrolytes urgently 1

Resumption of Home Medications

• Resume oral feeding as soon as possible after herniorrhaphy 2
• Restart home diabetes medications with the first meal 2
• For Type 1 diabetes, resumption of basal-bolus regimen is essential 1

Critical Pitfall: Basal-bolus insulin coverage (basal plus premeal rapid-acting) is superior to correction-only sliding scale insulin and reduces perioperative complications 1

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Key Safety Considerations

Avoid These Common Errors:

• Never use correction-only sliding scale insulin alone without basal insulin in the postoperative period, as this increases complications 1
• Never rely solely on capillary glucose readings in patients with vasoconstriction; values of 70 mg/dL on fingerstick should be considered hypoglycemia and verified with laboratory measurement 1
• Never discontinue insulin in Type 1 diabetes, as ketoacidosis can develop within hours 3
• Never target normoglycemia (80-110 mg/dL) perioperatively, as this increases mortality risk without benefit 1

When to Consult Endocrinology:

• HbA1c >8% preoperatively 2
• Persistent glucose >180 mg/dL despite adjustments 2
• Diabetes discovered during preoperative evaluation 2
• Difficulty managing current diabetes regimen 2

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Evidence Quality Note

The 2024 American Diabetes Association guidelines 1 provide the most current and authoritative recommendations, supported by French Society of Anaesthesia guidelines 1 which offer detailed practical protocols. The target range of 100-180 mg/dL represents a consensus that balances reduction in morbidity/mortality against hypoglycemia risk, with multiple high-quality guidelines converging on this recommendation.