Low Body Mass Index Versus Obesity: Which is Worse During Cardiac Surgery?

INTRODUCTION: Obesity can cause many diseases and leads to poor prognosis in the course of many diseases. Some researchers report that obesity positively affects cardiac surgery, and they refer to this phenomenon as the “obesity paradox.” Although there are many articles in the literature on obesity, there are no detailed studies on low BMI, especially in cardiac surgery. We wonder whether an extremely low body mass index is a risk factor, similar to obesity, in cardiac surgery patients.
METHODS: We conducted an analysis of the data from 786 patients who underwent elective isolated coronary artery bypass surgery in the last two years. The patients were categorized into four groups based on their BMI: Low BMI (<18.5 kg/m², n=72), Normal BMI (18.5-24.9 kg/m², n=228), Overweight BMI (25.0-29.9 kg/m², n=321), and Obese BMI (≥30.0 kg/m², n=166). Demographic data, co-existing diseases, surgical techniques, cross-clamp times, postoperative bleeding, ICU stay, and extubation times were recorded and compared across the groups. The bleeding index and the transfusion index were calculated and compared.
RESULTS: Although the number of grafts used was the same for all groups, the cross-clamp and total operation times were significantly longer for obese patients. During the postoperative intensive care follow-up, intubation times were also much longer for obese patients. Similarly, the amount of postop-erative drainage was statistically significantly higher in obese patients. On the other hand, it was observed that the “bleeding index” was significantly higher in patients with LBMI (p<0.001). When comparing blood products, it was found that fresh frozen plasma and erythrocyte suspension were used in significantly higher numbers in the OBMI group (p<0.001).
DISCUSSION AND CONCLUSION: Obesity remains an independent risk factor in cardiac surgery. In light of the information obtained in our current study, the bleeding index in patients with low BMI (BMI<18.5 kg/m2) is much higher than in obese patients. Patients with lower BMI require more blood transfusions than obese patients, indicating that low BMI is also a risk factor in cardiac surgery.