Achieving Safe Liberation During Weaning From VV-ECMO in Patients With Severe ARDS: The Role of Tidal Volume and Inspiratory Effort.

backgroundWeaning from venovenous extracorporeal membrane oxygenation (VV-ECMO) has not been not well studied. VV-ECMO can be discontinued when patients tolerate noninjurious mechanical ventilation (MV) during a sweep gas-off trial (SGOT). However, predictors of safe liberation are unknown. RESEARCH QUESTION: Can safe liberation from VV-ECMO be predicted at the bedside? STUDY DESIGN AND

methodsTwo observational studies of adults weaned from VV-ECMO for severe ARDS at Toronto General Hospital were conducted. MV settings, respiratory mechanics, and clinical variables were analyzed to predict safe liberation from VV-ECMO, defined a priori as avoida7ce of ECMO recannulation, increased MV support, need for rescue therapy, or hemodynamic instability developed within 48 h following decannulation.

resultsDuring both studies, 83 patients were weaned from VV-ECMO, 21 (25%) of whom did not meet the criteria for safe liberation. In the retrospective study, higher tidal volume per predicted body weight (OR, 1.58; 95% CI, 1.05-2.40; P = .03) and heart rate (OR, 1.07; 95% CI, 1.022-1.15; P = .01) 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 = .63) and sequential organ failure assessment score (OR, 1.16; 95% CI, 0.86-1.56; P = .34). Change in ventilatory ratio had an imprecise association (OR, 2.7; 95% CI, 0.94-7.95; P = .06) with unsafe liberation when adjusted for age (OR, 1.03; 95% CI, 0.96-1.10; P = .42), sequential organ failure assessment score (OR, 1.11; 95% CI, 0.81-1.51; P = .52), and heart rate (OR, 1.07; 95% CI, 1.01-1.13; P = .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] cm H

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