What are the preoperative clearance recommendations for a patient with diabetes (Diabetes Mellitus) on insulin with a Hemoglobin A1c (HbA1c) of 8% undergoing knee replacement surgery?

Preoperative Clearance for Knee Replacement in Diabetic Patient on Insulin with A1C 8%

This patient with an A1C of 8% meets the acceptable threshold for proceeding with elective knee replacement surgery, as current guidelines recommend an A1C goal of <8% for elective surgeries whenever possible. 1, 2

Preoperative Assessment and Clearance

Glycemic Control Status

• The patient's A1C of 8% is at the upper acceptable limit for elective surgery clearance. 1, 2
• While some institutions have developed optimization programs to lower A1C prior to surgery, the current evidence-based threshold supports proceeding at this level. 1
• The American Diabetes Association 2024-2025 guidelines explicitly state the A1C goal should be <8% (<63.9-64.0 mmol/L) whenever possible for elective surgeries. 1

Additional Preoperative Risk Assessment Required

• Perform a comprehensive cardiac risk assessment, as this patient is at high risk for ischemic heart disease. 1
• Evaluate for autonomic neuropathy, which increases perioperative risk. 1
• Assess renal function, as this affects medication management and surgical risk. 1

Perioperative Medication Management

Day Before Surgery

• Reduce the evening basal insulin dose by 25% compared to usual dosing - this approach is more likely to achieve perioperative blood glucose goals with lower hypoglycemia risk. 1
• Continue all insulin as prescribed until the evening before surgery with this 25% reduction. 1

Day of Surgery - Morning Instructions

• Hold all oral glucose-lowering agents (if any are being used). 1, 2
• Administer 75-80% of the usual long-acting basal insulin analog dose (or 50% of NPH if that is being used). 1, 2
• If the patient is on metformin, ensure it is held on the day of surgery. 1, 2
• If the patient is on SGLT2 inhibitors, these must be discontinued 3-4 days before surgery. 1, 2

Perioperative Glucose Targets

Target Blood Glucose Range

• Maintain blood glucose between 100-180 mg/dL (5.6-10.0 mmol/L) throughout the perioperative period. 1, 2
• This target should be achieved within 4 hours of surgery. 1, 2
• Do not attempt stricter glycemic control (<100 mg/dL or 80-180 mg/dL range) - tighter targets do not improve outcomes and significantly increase hypoglycemia risk. 1, 2

Monitoring Requirements

• Monitor blood glucose at least every 2-4 hours while the patient is NPO (nothing by mouth). 1, 2
• Use point-of-care glucose monitoring; continuous glucose monitoring (CGM) should not be used alone during surgery. 1, 2
• Administer short- or rapid-acting insulin as needed for correction. 1, 2

Postoperative Insulin Management

Insulin Regimen Strategy

• Implement a basal-bolus insulin regimen (basal insulin plus premeal short- or rapid-acting insulin) rather than correction-only insulin. 1, 2
• This approach has been associated with improved glycemic outcomes and lower rates of perioperative complications in noncardiac general surgery patients compared to reactive, correction-only coverage. 1, 2
• Continue to target blood glucose 100-180 mg/dL in the postoperative period. 2

Evidence-Based Rationale for A1C 8% Threshold

Supporting Evidence

• The most recent 2024-2025 American Diabetes Association guidelines consistently recommend A1C <8% as the target for elective surgeries. 1
• Research evidence shows mixed results regarding A1C thresholds: one large retrospective study of 40,491 total knee arthroplasty patients found no significantly increased risk of revision, deep infection, or DVT in diabetic patients (regardless of HbA1c level) compared to non-diabetic patients. 3
• However, other studies demonstrate that HbA1c ≥8% is associated with increased wound complications (OR 6.07) and superficial surgical site infections (OR 6.1) after total knee arthroplasty. 4, 5

Clinical Interpretation

• Given the conflicting research evidence but consistent guideline recommendations, proceeding with surgery at A1C 8% is appropriate, but the patient should be counseled about potentially increased wound complication risk. 4, 5
• The focus should shift to meticulous perioperative glucose control (100-180 mg/dL target) rather than delaying surgery for further A1C optimization. 1, 2

Critical Pitfalls to Avoid

• Do not delay surgery to achieve A1C <7% - the guideline threshold is <8%, and attempting tighter preoperative control may not be beneficial. 1
• Do not use correction-only insulin postoperatively - basal-bolus coverage is superior for outcomes. 1, 2
• Do not target blood glucose <100 mg/dL perioperatively - this increases hypoglycemia without improving outcomes. 1, 2
• Do not give full insulin doses on the morning of surgery - this significantly increases hypoglycemia risk. 1
• Do not forget the 25% reduction in evening basal insulin the night before surgery - this evidence-based adjustment improves perioperative glucose control. 1