Diabetes is not an independent risk factor for adverse early outcomes after coronary artery bypass grafting surgery, according to a large, retrospective study of patients who underwent the procedure over a 10-year period at a single institution.
This result may be due to improvements in management of glucose levels, according to a report by Dr. Pedro E. Antunes and colleagues.
Up to one-quarter of the patients undergoing coronary artery bypass grafting surgery (CABG) have diabetes. Previous reports have been conflicting regarding the negative impact of diabetes on short-term mortality and morbidity in patients undergoing CABG, with older studies finding a clearer relationship between diabetes and worse outcomes, the authors wrote.
In this study, 4,567 patients underwent isolated CABG over a 10-year period at the Hospitais da Universidade, Coimbra, Portugal. Overall, the rate of diabetes mellitus was 22% in these patients, ranging from 19% at the beginning of the study in 1992 to 27% at the end of the study in 2001—a significant decade trend (Eur. J. Cardiothorac. Surg. 2008;34:370–5). The study did not distinguish type 2 from type 1 diabetes.
The diabetic patients showed a significantly worse case-mix, compared with the nondiabetic patients according to the researchers. Diabetic patients had a higher mean age, a higher mean body mass index, and a higher proportion of patients with dyslipidemia, anemia, cardiomegaly, renal failure, peripheral vascular disease, cerebrovascular, and other comorbidities.
Perioperative glucose control in diabetic patients aimed at between 120 and 160 mg/dL. They received a standard sliding scale of subcutaneous insulin injection pre- and postoperatively, and in the operative room and ICU they received continuous intravenous insulin infusions.
The overall in-hospital mortality was 0.96% (44 individuals). There was no significant difference in mortality rate for the diabetic and nondiabetic groups (0.9% and 1.0%, respectively). Multivariate analysis showed that the presence of diabetes was not an independent predictor of in-hospital mortality.
As for in-hospital morbidity events, univariate analysis showed that diabetes was significantly associated only with cerebrovascular accident and prolonged length of stay. However, these associations disappeared in multivariate analysis, and only the development of mediastinitis in the diabetic patients showed significance.
“Better blood glucose management in the perioperative period improves early outcomes in diabetic patients subjected to CABG,” the authors reported.
Limitations to the study reported by the authors include that it is observational and retrospective.