Purpose: In diabetics, elevated preoperative hemoglobin A1c (HbA1c) levels are associated with increased complication rates after cardiac surgery. While many non-diabetics also have elevated HbA1c, the relationship with outcome in these patients is not well understood. Therefore, in a cohort of non-diabetic patients, we tested the hypothesis that preoperative HbA1c is associated with early mortality risk after cardiac surgery.
Methods: In this retrospective observational study, we accessed data from a prospectively collected quality assurance database for a cohort of 1,474 non-diabetic elective cardiac surgery patients with documented preoperative HbA1c levels. The relationship of HbA1c with death within 30 days of surgery was examined using logistic regression modeling. Acute kidney injury and infection were similarly assessed using multivariable linear and logistic regression.
Results: Thirty-one percent of patients (n = 456) had elevated HbA1c values (>6.0%). Patients with elevated HbA1c had higher fasting and peak intraoperative blood glucose values. Also, an elevated HbA1c level was independently associated with increased 30-day mortality (odds ratio 1.53 per percent increase [1.24-1.91]; P = 0.0005). This relationship persisted even after "borderline" diabetics were excluded. Furthermore, acute kidney injury was associated with elevated baseline HbA1c (P = 0.01). No association was found between HbA1c and postoperative infection risk (P = 0.48).
Conclusion: In non-diabetics, an elevated preoperative HbA1c level (>6.0%) is independently associated with significantly greater early mortality risk after elective cardiac surgery. Our findings suggest that HbA1c may have value as a screening tool to identify high-risk non-diabetic cardiac surgery patients.