The association between body mass index and outcome after coronary artery bypass grafting operations

Abstract

OBJECTIVES: This investigation was undertaken to analyse the association between body mass index (BMI) and morbidity after coronary artery bypass graft (CABG) operations. METHODS: The setting was a cardiovascular intensive care unit (ICU) of a tertiary medical referral centre. This was a retrospective review; patients were classified according to their BMI into five groups: underweight <18.5 kg/m2; normal weight 18.5-24.9 kg/m2; overweight 25-29.9 kg/m2; Class I obesity 3034.9 kg/m2; and Class II/III obesity >35 kg/m2. We included patients who underwent isolated CABG between January 3, 2006 and March 8, 2011. After including only the initial operation or admission in patients with more than one operation or hospital admission and excluding patients with any missing variable, 3470 patients remained in the analyses. The primary outcomes analysed were hospital mortality and pulmonary and infection morbidities. We secondarily assessed the association between BMI category and each of the three outcomes. RESULTS: Respective mortality, and pulmonary and infection morbidity occurrence rates were: 8.7, 13.0 and 13.0% for the underweight; 2.4, 8.0 and 4.8% for the overweight; 1.8, 10.9 and 5.6% for the Class I obesity group; and 2.7, 11.1 and 5.7% for the Class II/III obesity group, vs 2.3, 7.0 and 6.2% for the normal weight group. Class I and II/III obesity patients were more likely to have pulmonary morbidity compared with the normal weight group, after adjusting for the potential confounding variables. CONCLUSIONS: Class I and Class II/III obesity (BMI ≥ 30 kg/m2) was associated with increased pulmonary morbidity after CABG operations. There was no difference in mortality or infection morbidity in any BMI group compared with the normal group.