Obesity is not a risk factor for significant adverse outcomes after cardiac surgery

Obese patients undergoing cardiac surgery are often thought to have prohibitive perioperative risk despite the lack of sufficient data to support this assumption.

To assess the significance of obesity as a risk factor in patients undergoing cardiac surgery, we analyzed data from 2299 patients undergoing procedures requiring cardiopulmonary bypass from January 1, 1991, to December 31, 1993. Obesity was defined by use of the body mass index, defined as weight in kilograms divided by height in meters squared. Potential adverse outcomes analyzed included operative mortality, deep sternal wound infection, superficial sternal wound infection, infection at the saphenous vein harvest site, stroke, renal failure, adult respiratory distress syndrome, prolonged mechanical ventilation, pneumonia, sepsis, atrial arrhythmias, pulmonary embolism, need for early reexploration for bleeding, and ventricular arrhythmias. To control for the confounding effects of other risk factors, we performed a multivariate logistic regression analysis. Potential covariates considered in the logistic model included age, sex, race, history of reoperation, congestive heart failure, prior myocardial infarction, renal failure, diabetes, hypertension, chronic obstructive pulmonary disease or stroke, and cardiopulmonary bypass and aortic cross-clamp time. Twenty-five percent of patients (567/2299) were classified as obese. The results of the multivariate regression demonstrated that obesity was a risk factor only for superficial sternal wound infection (P < .001; odds ratio, 2.3), leg infections (P = .005; odds ratio, 1.8), and atrial dysrhythmias (P = .04; odds ratio, 1.2). Notably, obesity did not predispose toward increased pulmonary complications or deep sternal wound infection (P = .65).

With the exception of superficial wound complications and atrial dysrhythmias, obesity is not a significant multivariate risk factor for adverse outcomes. The results indicate that obese patients may safely undergo cardiac surgery with due attention to technical considerations designed to minimize wound complications.