Glycated hemoglobin HbA_1c – a new risk marker for the outcome of cardiac surgery?

Introduction: About 30% of patients undergoing cardiac surgery are diabetic, and glycated hemoglobin (HbA_1c) is a reliable marker for long-term glucose control. The aim of our study was to examine whether tight glucose control before a cardiac operation results in a better outcome of the surgical treatment.

Material and methods: We performed a retrospective record review of 350 diabetic patients undergoing cardiac surgery in our institution. Preoperative glycemia control was assessed by measurement of the glycated hemoglobin level. The patient population was divided into three groups: group I – patients with HbA_1c below 7% (n = 195); group II – patients with HbA_1c between 7% and 8% (n = 88); and group III – patients with HbA_1c above 8% (n = 67).

Results: The demographic data and operating risk in all groups of patients were similar. There were 2 deaths (1.02%) in group I, 2 deaths (2.27%, p = 0.78) in group II and 3 deaths (4.47%, p = 0.20) in group III. Cardiac accidents occurred in 9 patients (4.60%) from group I, 7 patients (7.95%, p = 0.20) from group II, and in 6 patients (9.05%, p = 0.40) from group III. Cerebrovascular accidents (CVA) occurred in 7 (3.58%), 5 (5.68%, p = 0.67) and 5 (7.46%, p = 0.61) patients, respectively. Acute renal dysfunction requiring renal replacement therapy occurred in 4 patients from group I (2.05%), 3 patients from group II (3.40%, p = 0.78) and 4 patients from group III (5.97%, p = 0.23).

Conclusions: A large percentage of diabetic patients referred for cardiac operations have poorly controlled glycemia. Optimal preoperative glycemia control results in lower postoperative mortality and morbidity. In addition, the preoperative HbA_1c level is a good indicator of the risk of postoperative complications in diabetic patients undergoing cardiac operations.