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 his colleagues.
Up to one-quarter of the patients who undergo coronary artery bypass grafting (CABG) surgery 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-long trend (Eur. J. Cardiothorac. Surg. 2008;34:370–5).
The study did not distinguish type 2 from type 1 diabetes, the authors noted.
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, and cerebrovascular and other comorbidities.
Perioperative glucose control in diabetic patients was aimed at achieving levels between 120 and 160 mg/dL. They received a standard sliding scale of subcutaneous insulin injection pre- and postoperatively; in the operating room and the ICU they received continuous intravenous insulin infusions.
The overall in-hospital mortality was 0.96% (44 patients). There was no significant difference in mortality rate for the diabetic and nondiabetic groups: The mortality rates for the two groups were 0.9% and 1.0%, respectively, Dr. Pedro E. Antunes and his colleagues reported.
Multivariate analysis showed that the presence of diabetes was not an independent predictor of in-hospital mortality.
However, increasing age, reoperation, peripheral vascular disease, left ventricular dysfunction with an ejection fraction less than 40%, and nonelective surgery were all independent predictors of in-hospital death.
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.
The researchers concluded that “despite the worsening case mix, in our experience diabetic patients could be surgically revascularized with low mortality and morbidity rates, comparable to those of nondiabetic patients.”
Limitations of the study reported by the authors include that it is observational and retrospective, although they commented that it was based on prospectively collected data and had a large cohort size, which adds strength to the power of the analysis.