Association between body mass index and clinical outcomes in patients with out-of-hospital cardiac arrest undergoing extracorporeal cardiopulmonary resuscitation: A multicenter observational study

Background: We examined the association between body mass index (BMI) and outcomes in patients with out-of-hospital cardiac arrest (OHCA) undergoing extracorporeal cardiopulmonary resuscitation (ECPR).Methods: We retrospectively analyzed the database of an observational multicenter cohort in Japan. Adult patients with OHCA of cardiac etiology who received ECPR between 2013 and 2018 were categorized as follows: underweight, BMI < 18.5; normal weight, BMI = 18.5-24.9; overweight, BMI = 25-29.9; and obese, BMI >= 30 kg/m(2). The primary outcome was in-hospital mortality; secondary outcomes were unfavorable neurological outcomes at discharge (cerebral performance category >= 3) and ECPR-related complications. BMI's association with outcomes was assessed using a logistic regression model adjusted for age, sex, comorbidities, witness/bystander CPR, initial rhythm, prehospital return of spontaneous circulation, and low-flow time.Results: In total, 1,044 patients were analyzed. Their median age was 61 (IQR, 49-69) years; the median BMI was 24.2 (21.5-26.9) kg/m(2). The overall rates of in-hospital mortality, unfavorable neurological outcome, and ECPR-related complications were 62.2%, 79.9%, and 31.7%, respectively. In multivariate analysis, the overweight and obese groups had higher in-hospital mortality odds than the normal BMI group (odds ratio [95%CI], 1.37 [1.02-1.85], p = 0.035; and 2.09 [1.31-3.39], p < 0.001, respectively). The odds ratio for unfavorable neurological outcomes increased more in the obese than in the normal BMI group (3.17 [1.69-6.49], p < 0.001). ECPR-related complications were not significantly different among groups.Conclusions: In OHCA patients undergoing ECPR, a BMI >= 25 kg/m(2) was associated with increased in-hospital mortality, and a BMI >= 30 kg/m(2) was also associated with a worse neurological outcome.