Does Weight Matter? Outcomes in Adult Patients on Venovenous Extracorporeal Membrane Oxygenation When Stratified by Obesity Class

BACKGROUND: Many believe obesity is associated with higher rates of mortality in the critically ill. The purpose of this retrospective observational study is to evaluate the association between body mass index (BMI) and survival in patients receiving venovenous (VV) extracorporeal membrane oxygenation (ECMO) for acute hypoxic or hypercarbic respiratory failure. METHODS: All of the patients admitted to a dedicated VV ECMO unit were included. Patients <18 years of age, listed for lung transplant, or underweight were excluded. ECMO outcomes, including hospital length of stay and survival to discharge, were analyzed after stratification according to BMI. Multivariate logistic and linear regression techniques were used to assess variables associated with the outcomes of death and length of stay, respectively. RESULTS: One hundred ninety-four patients with a median BMI of 35.7 kg/m(2)(33-42 kg/m(2)) were included. Obese patients were older, had higher creatinine levels, and required higher levels of positive end-expiratory pressure and mean airway pressure at time of cannulation. Survival to discharge in any group did not differ when stratified by BMI classification (P= .36). Multivariable regression did not reveal any association with greater odds of death or longer length of stay when controlling for BMI and other variables. CONCLUSIONS: We did not detect an association between obesity and increased mortality in patients requiring VV ECMO for acute hypoxic or hypercarbic respiratory failure. These data suggest that obesity alone should not exclude candidacy for VV ECMO. Evidence for the "obesity paradox" in this population of VV ECMO patients may be supported by these data.