Venovenous extracorporeal membrane oxygenation for acute respiratory distress syndrome: a systematic review and meta-analysis

Background Use of extracorporeal membrane oxygenation (ECMO) in adults with severe acute respiratory distress syndrome has increased in the past 10 years. However, the efficacy of venovenous ECMO in people with acute respiratory distress syndrome is uncertain according to the most recent data. We aimed to estimate the effect of venovenous ECMO on mortality from acute respiratory distress syndrome. Methods In this systematic review and meta-analysis, we searched MEDLINE (including MEDLINE In-Process and Epub Ahead of Print), Embase and the Wiley search platform in the Cochrane database for randomised controlled trials and observational studies with matching of conventional mechanical ventilation with and without venovenous ECMO in adults with acute respiratory distress syndrome. Titles, abstracts, and full-text articles were screened in duplicate by two investigators. Data for study design, patient characteristics, interventions, and study outcomes were abstracted independently and in duplicate. Studies were weighted with the inverse variance method and data were pooled via random-effects modelling. We calculated risk ratios (RRs) and 95% CIs to summarise results. The primary outcome was 60-day mortality across randomised controlled trials. The Grading of Recommendations Assessment, Development and Evaluation (GRADE) guidelines were used to rate the quality of evidence Findings We included five studies, two randomised controlled trials and three observational studies with matching techniques (total N=773 patients). In the primary analysis, which included two randomised controlled trials with a total population of 429 patients, 60-day mortality was significantly lower in the venovenous ECMO group than in the control group (73 [34%] of 214 vs 101 [47%] of 215; RR 0.73 [95% CI 0.58-0.92]; p=0.008; 120%). The GRADE level of evidence for this outcome was moderate. Three studies included data for the incidence of major haemorrhage in the ECMO group. 48 (19%) of the 251 patients in these three studies had major haemorrhages. Interpretation Compared with conventional mechanical ventilation, use of venovenous ECMO in adults with severe acute respiratory distress syndrome was associated with reduced 60-day mortality. However, venovenous ECMO was also associated with a moderate risk of major bleeding. These findings have important implications surrounding decision making for management of severe acute respiratory distress syndrome at centres providing venovenous ECMO.