Objectives
Obesity is associated with increased burden of cardiovascular risk factors, morbidity and mortality. However, several studies have counterintuitively shown better outcome after cardiac surgery in obese than in normal weight patients, a phenomenon known as obesity paradox. Furthermore, obesity has been linked with decreased need of red blood cell transfusions. The purpose of this study was to evaluate the impact of body mass index on 30-day mortality and red blood cell transfusions in patients undergoing cardiac surgery, a clinically important topic with conflicting previous data.
Methods
We retrospectively investigated 1691 patients who underwent coronary and/or valve or aortic root surgery using cardiopulmonary bypass between 2013 and 2016. The patients were categorized by body mass index based on World Health Organization classification. For analysis, logistic regression was used with adjustment for potential confounding factors.
Results
Of the patients 28.7% were normal weight, 43.3% overweight, 20.5% mildly obese, and 7.5% severely obese. 30-day mortality was 1.9% without significant differences between the body mass index groups. 41.0% of patients received red blood cell transfusion. Overweight (odds ratio [OR] 0.75, 95% confidence interval [CI] 0.56-0.99, P = 0.045), mildly (OR 0.65, 95% CI 0.46-0.92, P = 0.016) and severely obese (OR 0.41, 95% CI 0.24-0.70, P =0.001) patients needed less frequently red blood cell transfusions than patients with normal weight.
Conclusions
Obesity was not associated with 30-day mortality but was associated with lower use of red blood cell transfusions in cardiac surgery.