What peri‑operative insulin regimen should a diabetic patient undergoing elective knee arthroplasty follow?

Perioperative Insulin Management for Knee Arthroplasty

For diabetic patients undergoing elective knee arthroplasty, give 75-80% of the usual long-acting insulin dose (or half of NPH dose) on the morning of surgery, withhold all oral agents, target glucose 100-180 mg/dL perioperatively, and transition to basal-bolus insulin postoperatively rather than correction-only insulin. 1, 2, 3

Preoperative Insulin Adjustments (Day of Surgery)

Morning of Surgery:

• Withhold all oral hypoglycemic agents including metformin on the day of surgery 1, 2
• Give 75-80% of usual long-acting insulin analog dose (glargine, detemir, degludec) 1, 2, 3
• Give 50% of usual NPH insulin dose if patient uses NPH 1, 2
• Hold all prandial (mealtime) insulin since patient will be NPO 1

Evening Before Surgery:

• Consider reducing basal insulin by 25% the evening before surgery to achieve better perioperative glucose control with lower hypoglycemia risk 2, 3
• This approach is supported by recent evidence showing improved target glucose achievement compared to usual dosing 1, 2

Critical Medication Timing

• SGLT2 inhibitors must be discontinued 3-4 days before surgery to prevent euglycemic diabetic ketoacidosis, which can occur even with normal glucose levels 2, 3
• Metformin is held only on the day of surgery, not earlier 1, 2

Perioperative Glucose Targets

Target glucose range: 100-180 mg/dL (5.6-10.0 mmol/L) throughout the entire perioperative period 1, 2, 3

Why Not Tighter Control?

• Do not pursue targets <100 mg/dL as this significantly increases hypoglycemia risk without improving outcomes 1, 2, 3
• Studies demonstrate that perioperative glycemic control tighter than 80-180 mg/dL does not improve outcomes and causes more hypoglycemia 1, 2

Intraoperative Monitoring

• Monitor blood glucose every 4-6 hours minimum while patient is NPO 1, 2
• More frequent monitoring (every 2-4 hours) is recommended during active surgery 2, 4
• Administer short- or rapid-acting insulin as needed to maintain target range 1, 2

Postoperative Insulin Management

Use basal-bolus insulin regimen, NOT correction-only insulin 2, 3, 5

Why Basal-Bolus is Superior:

• Basal-bolus regimens (basal insulin plus premeal rapid-acting insulin) improve glycemic outcomes and reduce perioperative complications compared to correction-only insulin in noncardiac surgery patients 2, 3, 5
• Correction-only ("sliding scale") insulin without basal coverage is associated with worse outcomes and is not recommended 2, 3, 5

Transition from IV to Subcutaneous Insulin (if IV insulin was used):

• Stop IV insulin only after subcutaneous basal insulin is given 1, 3
• Administer basal insulin 2-4 hours before stopping IV insulin to prevent rebound hyperglycemia 3
• The most widely used transition model: 50% of total daily IV insulin dose becomes basal insulin, 50% becomes rapid-acting analog 1
• Alternative approach: 80% of IV insulin dose as basal insulin plus rapid-acting insulin at first meal 1
• Wait until IV insulin infusion rate is <3 units/hour before transitioning, as higher rates indicate major insulin resistance and over-risk of complications 1

Practical Postoperative Regimen:

• Continue monitoring glucose every 2-4 hours while NPO 2
• Resume basal insulin at appropriate dose based on preoperative regimen or IV insulin requirements 1
• Add prandial rapid-acting insulin with meals, adjusting for carbohydrate intake 1
• Provide correction doses of rapid-acting insulin for glucose >180 mg/dL 1, 2

Special Considerations for Knee Arthroplasty

Preoperative Optimization:

• Target HbA1c <8% for elective surgeries to reduce surgical risk, mortality, infection rates, and length of stay 2, 3, 6
• Poor preoperative glycemic control (HbA1c >8%) adversely influences functional recovery at 1 year post-arthroplasty 7
• Patients with inadequate glycemic control exhibit significantly smaller improvements in WOMAC and SF-36 scores at 1 year 7

Risk Factors for Postoperative Hyperglycemia:

• Diabetes, revision surgery, male sex, and obesity (including morbid obesity) are independent factors causing significant glycemic elevation after joint arthroplasty 8
• All patients undergoing knee arthroplasty should be evaluated for hyperglycemia starting in the post-anesthesia care unit, regardless of diabetes status 8

Management of Hypo- and Hyperglycemia

Hypoglycemia (<60 mg/dL or 3.3 mmol/L):

• Administer glucose immediately even without clinical symptoms 1
• Use oral glucose if patient is conscious and able to swallow 1
• Use IV glucose if patient is unconscious or unable to swallow 1
• For glucose 70-100 mg/dL (3.8-5.5 mmol/L) with symptoms, give glucose 1

Severe Hyperglycemia (>300 mg/dL or 16.5 mmol/L):

• In Type 1 diabetes or insulin-treated Type 2 diabetes, check for ketosis 1
• Administer rapid-acting insulin and ensure adequate hydration 1
• If ketosis present, suspect diabetic ketoacidosis and escalate care 1

Critical Pitfalls to Avoid

• Never use correction-only insulin without basal insulin in postoperative knee arthroplasty patients—this is associated with worse outcomes 2, 3, 5
• Never continue SGLT2 inhibitors within 3-4 days of surgery—risk of euglycemic DKA 2, 3
• Never stop IV insulin without prior subcutaneous basal insulin—causes rebound hyperglycemia 3
• Never pursue glucose targets <100 mg/dL perioperatively—increases hypoglycemia without benefit 2, 3
• Never delay surgery for HbA1c optimization unless >8%—balance surgical timing with glycemic optimization 2, 3, 6

Insulin Pump Patients

• Reconnect personal insulin pump as soon as patient can manage autonomously postoperatively 1
• If patient cannot manage pump autonomously, initiate basal-bolus subcutaneous insulin regimen immediately 1