Impact of body mass index and albumin on morbidity and mortality after cardiac surgery

Abstract

Objective: Extremely thin and overly obese patients may not tolerate cardiac surgery as well as other patients. A retrospective study was conducted to determine whether the extremes of body mass index (weight/height² [kg/m²]) and/or cachexia increased the morbidity and mortality associated with cardiac operations. Methods: Body mass index was used to objectively measure “thinness” (body mass index < 20) and “heaviness” (body mass index > 30); preoperative serum albumin was used to quantify nutritional status and underlying disease. Data were gathered between 1993 and 1997 from 5168 consecutive patients undergoing coronary artery bypass or valve operations, or both. Results: No significant correlations were observed between body mass index and preoperative albumin levels. Low body mass index (<20) and low albumin level (<2.5 g/dL) were each independently associated with increased mortality after cardiopulmonary bypass (P ≤ .0005). Operative mortality was highest among those with both low body mass index and low albumin level. Multivariable logistic regression, adjusting for potentially confounding variables, demonstrated that an albumin level of less than 2.5 g/dL was independently associated with increased risk of reoperation for bleeding, postoperative renal failure, and prolonged ventilatory support, intensive care unit stay, and total length of stay. A body mass index of more than 30 was associated with increased sternal wound infection and saphenous vein harvest site infection. Conclusions: Hypoalbuminemia and low body mass index each independently predict increased morbidity and mortality after cardiac operations. Preoperative risk stratification with the use of body mass index and serum albumin may help to identify subgroups of patients at high risk for adverse outcomes after cardiac operations. (J Thorac Cardiovasc Surg 1999;118:866-73)