Body mass index and echocardiography in refractory ARDS treated with veno-venous extracorporeal membrane oxygenation

The aims of the present investigation, performed in 118 consecutive patients with refractory ARDS treated with veno-venous extracorporeal membrane oxygenation (VV-ECMO), were as follows: (a) to assess ICU mortality in overweight, obese and morbid obese patients in respect to normal weight; (b) to evaluate echocardiographic findings according to BMI subgroups. Echocardiography was performed before VV-ECMO implantation. Forty-five patients (38.1%) showed normal BMI, 37 patients (31.4%) were overweight and the remaining were obese (21.2%), or morbid obese (9.3%). Morbid obese showed the lowest ICU mortality rate (p = 0.003). No differences were detectable among BMI subgroups in echocardiographic findings apart from the fact that obese patients showed the lowest incidence of LV dysfunction (p = 0.015). At stepwise regression analysis the following variables were independent predictor of ICU mortality (when adjusted for age): RV dilatation (OR 4.361, 95 % CI 1.809-10.512, p < 0.001), BMI (OR 0.884, 95% CI 0.821-0.951, p < 0.001). In other terms, the presence of RV dilatation is an independent predictor of ICU mortality. In refractory ARDS treated with VV-ECMO, BMI > 30 kg/m² is common (accounting for one-third of the entire population) but it is not associated with a worse outcome, so that it cannot be considered per se a contraindication to ECMO implantation. The incidence of RV dilatation and failure, which are known to negatively affect prognosis in ARDS patients, were comparable among BMI subgroups.