Impact of body mass index on early outcomes in patients undergoing cardiac surgery

The relationship between body mass index (BMI) and cardiovascular diseases (CVD) is well known, highlighting that a high BMI (>24.9 kg/m²) is associated with an increased risk of developing these conditions. However, a low BMI (<18.5 kg/m²) has also been linked to the development of CVD, particularly concerning heart failure, arrhythmias, vascular diseases, and an increased mortality rate following acute myocardial infarction, due to factors such as sarcopenia and reduced cardiac reserve. In addition, it has been shown that BMI correlates directly with early outcomes such as mediastinal hemorrhage, hypovolemia, arrhythmias, and perioperative mortality in patients undergoing cardiac surgery.

The aim of this study was to describe the association between BMI and the development of perioperative and postoperative complications in patients undergoing cardiac surgery, regardless of preoperative diagnosis.

A descriptive retrospective observational study was conducted on patients over 18 years old who underwent cardiac surgery with cardiopulmonary bypass. The study evaluated BMI and the development of cardiovascular diseases (CVD), comparing four groups: low BMI (<18.5 kg/m²), normal BMI (18.5 to 24.9 kg/m²), overweight (24.9 to 29.9 kg/m²), and obesity (>30 kg/m²). The patients were admitted to the cardiovascular intensive care unit from June 1, 2022, to December 31, 2023. The study included demographic, surgical, hemodynamic variables, outcomes, and intrahospital mortality.

A sample of 555 patients was included, of which 56.8% were men and 43.2% were women. 61% had a high BMI, 2.7% had a low BMI, and the rest had a normal BMI. We identified that patients with a low BMI had a higher likelihood of developing various immediate postoperative complications, including mediastinal hemorrhage (OR 1.73; 95% CI 0.47-6.30), postcardiotomy low cardiac output syndrome (OR 3.35; 95% CI 1.11-10.11), acute liver failure (OR 1.95; 95% CI 0.53-7.12), and postoperative atrial fibrillation (OR 2.59; 95% CI 0.86-7.76), which increased the need for blood product transfusions (OR 1.81; 95% CI 0.61-5.38). In contrast, patients with a high BMI had a lower incidence of perioperative and postoperative complications.

This retrospective analysis showed that BMI directly affects the development of early outcomes in patients undergoing cardiac surgery. Also, patients with a low BMI had a higher likelihood of developing these complications compared to patients with a high BMI.

Description postoperative outcomes