The Rate of Postoperative Mortality and Renal and Respiratory Complications are Increased in Patients with Extreme Obesity Undergoing Cardiac Surgery-A Retrospective Observational Cohort Study of 8848 Patients

Introduction: The importance of obesity as a potential risk factor in open heart surgery is well known. The epidemic of extreme obesity is an increasing public health concern and raises alerts regarding postoperative complications and mortality in patients undergoing cardiac surgery. The study aimed to analyze the impact of extreme obesity (BMI>40) on the frequency of postoperative complications, as well as early and delayed mortality compared to patients with a lower body mass. Materials and Methodology: This retrospective observational cohort study involved patients, over the age of 18, undergoing cardiac surgery with cardiopulmonary bypass at the Cardiac Surgery Department of the Pomeranian Medical University in Szczecin, Poland between January 1st, 2010 and December 31st, 2018. The patients included in the study were allocated into two subgroups depending on the BMI index (Group I BMI>40 vs Group II BMI<40). Results: A total of 8848 adult patients of both genders were included. Baseline characteristics for Group I and Group II were mean age 64.07 +/- 7.76 vs 65.10 +/- 9.68 years (p=0.123), mean BMI 42.13 +/- 2.44 vs 28.55 +/- 4.23 (p<0.001), with more females in Group I (58.04% vs 29.06%) and more males in Group II (70.94% vs 29.06%), p<0.001. The predicted perioperative risk using the EuroScore Logistics scale was higher in a group with BMI>40 (p<0.001). Regression analysis with adjustment for confounding factors showed a statistically significant relationship between BMI>40 and postoperative respiratory failure (OR=1.760, p=0.043), acute kidney injury AKIN2 (OR=2.082, p=0.044) and AKIN3 (OR=2.743, p=0.039). 30-day mortality in the univariate analysis showed a statistically significant relationship, however, after modifying the results with interfering factors, no statistical significance was obtained. Conclusion: The risk of postoperative acute respiratory failure and acute renal injury was increased in patients with BMI>40. The probability of 30-day survival of patients after cardiac surgery was much lower in people with extreme obesity, although it was related to the dominant comorbidities. The 10-year survival was comparable in both groups.