Body mass index and its impact on outcomes in CABG surgery: the paradox of obesity and underweight risks.

Objective: To explore the impact of BMI on the short-term mortality and morbidity of patients undergoing CABG. Study Design: Retrospective Cross Sectional study. Setting: Department of Cardiac Surgery Rehman Medical Institute, Peshawar, Pakistan. Period: 1st June 2017 to 31st December 2022. Methods: The data was collected from the data base of the cardiac surgery department. Results: Total of 2599 isolated CABG patients were included with mean age of 57.86±9.2 years. The majority was overweight (42%). Approximately 78.1% were male. Hypertension was our dominant co-morbidity (68.7%) followed by dyslipidemia (65.4%) & DM (50.1%). Majority of patients had NYHA-III symptoms (51.2%). A significant proportion of individuals who are classified as underweight are elderly. Generally, there is a significant increasing trend of DM & HTN incidence with increasing BMI. In terms of intra-operative parameters there is increasing trend of intra-operative transfusions and higher rate of IABP insertion in underweight patients. Generally the underweight patients has the higher trend of adverse outcomes (e.g., prolonged mechanical ventilation, blood product requirement, reopening & re-intubation), but not significant. However, they have significantly longer mechanical ventilation time compared to normal. On the other extreme, morbidly obese patients had the highest in-hospital mortality (11.3%) while overweight had the lowest (2.6%) with a P-value of 0.008. Multivariate regression analysis showed that mean age (P 0.034), cross-clamp time (P 0.018) & mechanical ventilation (P <0.001) were significantly associated with in-hospital mortality. Conclusion: Morbidly obese patients undergoing CABG surgery face significantly higher in-hospital mortality rate, conversely overweight patients exhibits the lowest mortality rates confirming a partial obesity paradox. However, underweight patients experience the worst outcomes, including increased requirements for postoperative blood transfusions, a higher incidence of surgical reopening, and significantly extended mechanical ventilation hours, which indicates either extreme of BMI group is associated with worst outcomes.