Mortality of patients with respiratory insufficiency and adult respiratory distress syndrome after surgery: the obesity paradox

Abstract

Introduction: Obesity has long been considered a risk factor for the development of various pathologies, yet evidence supporting increased risk of perioperative mortality in obese individuals developing postoperative complications is limited. Therefore, we sought to characterize the demographics of obese and nonobese individuals developing postoperative respiratory insufficiency (RI)/adult respiratory distress syndrome (ARDS) and to quantify the impact of obesity on in-hospital mortality among this patient population utilizing data collected for the Nationwide Inpatient Sample (NIS).

Methods: Nationwide Inpatient Sample data for each year between 1998 and 2007 were accessed. Entries were included if they underwent a surgical procedure and had a diagnosis of RI/ARDS following surgery. Patients fulfilling entry criteria were divided into those with and without obesity. In-hospital mortality was the primary outcome. A logistic regression model was fitted to elucidate if obesity was associated with increased odds for the outcome while controlling for age, gender, admission and procedure type, and comorbidity burden.

Results: We identified 9 149 030 admissions that underwent the included surgical procedures between 1998 and 2007. Of those, 5.48% had a diagnosis of obesity. The incidence of RI/ARDS was 1.82% among obese and 2.01% among nonobese patients. Obese patients whose postoperative course was complicated by RI/ARDS had a significantly lower incidence of the need for mechanical ventilation (50% vs 55%). In-hospital mortality was significantly lower compared to nonobese patients (5.45% vs 18.72%). For those patients with RI/ARDS requiring intubation, the in-hospital mortality rate was 11% for obese and 25% for nonobese patients. In the multivariate regression analysis, obesity was associated with a 69% reduction in the odds of in-hospital mortality in postoperative patients with RI/ARDS.

Conclusion: In our analysis, obesity was associated with a decreased incidence and adjusted odds for in-hospital mortality after surgery. Our results support the emerging concept of the "obesity paradox."