Hemoglobin A1c Testing for Preoperative Evaluation
You should order a hemoglobin A1c level (Option A) for this patient before proceeding with scheduled ankle surgery. 1, 2
Rationale for HbA1c Testing
The patient's most recent HbA1c was 6.8% five months ago, which is now outdated for surgical risk stratification. 2 Current perioperative diabetes guidelines emphasize the importance of recent HbA1c measurement to:
- Assess current glycemic control before elective surgery, as HbA1c reflects glucose control over the preceding 8-12 weeks and helps distinguish between well-controlled diabetes versus deteriorating control 3
- Risk stratify for perioperative complications, as elevated HbA1c predicts adverse surgical outcomes including mortality, infection, and wound complications 4
- Guide perioperative management decisions, particularly regarding insulin dosing and monitoring intensity 1, 2
Evidence-Based Thresholds
The French Society of Anaesthesia and Intensive Care Medicine identifies HbA1c >8% as representing preoperative glycemic imbalance that mandates referral to a diabetologist before proceeding with elective surgery. 2 The American Diabetes Association recommends targeting A1C <8% for elective surgeries to reduce surgical risk, mortality, and infection rates. 1, 2
Given that her previous HbA1c was 6.8% five months ago and her current fasting plasma glucose is elevated at 155 mg/dL (normal <100 mg/dL), there is concern that her glycemic control may have deteriorated. 3 This makes current assessment critical before proceeding with surgery.
Why Not the Other Options
Prothrombin time/INR (Option B) is not indicated as the patient is only on metformin, which does not affect coagulation, and there is no mention of anticoagulant use. 3
Transthoracic echocardiogram (Option C) would only be indicated if there were clinical signs of heart failure or specific cardiac concerns, which are not present in this case with normal vital signs and physical examination unremarkable except for the ankle pathology. 5
High-sensitivity cardiac troponin I (Option D) is not routinely indicated for preoperative evaluation in asymptomatic patients undergoing non-cardiac surgery, even with diabetes. 5
Clinical Context
The elevated fasting glucose of 155 mg/dL suggests suboptimal glycemic control despite dietary modifications and metformin therapy. 3 This finding, combined with the outdated HbA1c, creates uncertainty about whether she meets the recommended glycemic targets for safe elective surgery. 1, 2
A blood sugar level <180 mg/dL (10 mmol/L) before intervention decreases the risk of death, infection, and duration of stay. 3 While her current glucose is below this threshold, the HbA1c will provide essential information about chronic glycemic control that cannot be determined from a single glucose measurement. 3
Perioperative Management Implications
Once the HbA1c result is available:
- If HbA1c <8%: Proceed with surgery using standard perioperative glucose management (target 100-180 mg/dL, monitor every 2-4 hours while NPO, hold metformin day of surgery) 1, 5
- If HbA1c ≥8%: Consider delaying elective surgery and referring to endocrinology for optimization, as this threshold indicates inadequate control associated with increased perioperative risk 2
The HbA1c result will also help distinguish whether her elevated fasting glucose represents stress hyperglycemia versus worsening diabetes control requiring treatment intensification. 3