Weaning from venovenous extracorporeal membrane oxygenation (VV-ECMO) is not well studied. VV-ECMO can be discontinued when patients tolerate non-injurious mechanical ventilation (MV) during a sweep gas off trial (SGOT). However, predictors of safe liberation are unknown.

Can safe liberation from VV-ECMO be predicted at the bedside?

We conducted 2 observational studies of adults weaned from VV-ECMO for severe ARDS at Toronto General Hospital. We analyzed MV settings, respiratory mechanics and clinical variables to predict safe liberation from VV-ECMO, defined a priori as avoidance of ECMO recannulation, increase MV support, need for rescue therapy or hemodynamic instability developed within 48 hours after decannulation.

During both studies, 83 patients were weaned from VV-ECMO, of whom 21 (25%) did not meet criteria for safe liberation. In the retrospective study, higher tidal volume per predicted body weight (V_Tpbw, OR 1.58, 95%CI 1.05-2.40, P=0.03) and heart rate (HR, OR 1.07, 95%CI 1.01-1.13, P=0.02) at the end of SGOT were significantly associated with increased odds of unsafe liberation when adjusted for age (OR 1.02, 95%CI 0.95-1.09, P=0.63) and SOFA (OR 1.16, 95%CI 0.86-1.56, P=0.34). Change in ventilatory ratio (VR) had an imprecise association (OR 2.71, 95%CI 0.93-7.92, P=0.06) with unsafe liberation when adjusted for age (OR 1.03, 95%CI 0.96-1.10, P=0.42), SOFA (OR 1.11, 95%CI 0.81-1.51, P=0.52) and heart rate (OR 1.07, 95%CI 1.01-1.13, P=0.02). In the prospective study, patients who had unsafe liberation from VV-ECMO also had significantly higher inspiratory efforts (esophageal pressure swings 9 [7-13] vs 18 [7-25] cmH₂O, p=0.03), and worse outcomes (longer MV duration, ICU and hospital length of stay).

Patients with higher tidal volume, heart rate, ventilatory ratio, and esophageal pressures swings during SGOT were less likely to achieve safe liberation from VV-ECMO.