Systematic review and meta-analysis of complications and mortality of veno-venous extracorporeal membrane oxygenation for refractory acute respiratory distress syndrome

Abstract

Veno-venous extracorporeal membrane oxygenation (ECMO) for refractory acute respiratory distress syndrome (ARDS) is a rapidly expanding technique. We performed a systematic review and meta-analysis of the most recent literature to analyse complications and hospital mortality associated with this technique. Using the PRISMA guidelines for systematic reviews and meta-analysis, MEDLINE and EMBASE were systematically searched for studies reporting complications and hospital mortality of adult patients receiving veno-venous ECMO for severe and refractory ARDS. Studies were screened for low bias risk and assessed for study size effect. Meta-analytic pooled estimation of study variables was performed using a weighted random effects model for study size. Models with potential moderators were explored using random effects meta-regression. Twelve studies fulfilled inclusion criteria, representing a population of 1042 patients with refractory ARDS. Pooled mortality at hospital discharge was 37.7% (CI 95% = 31.8-44.1; I ² = 74.2%). Adjusted mortality including one imputable missing study was 39.3% (CI 95% = 33.1-45.9). Meta-regression model combining patient age, year of study realization, mechanical ventilation (MV) days and prone positioning before veno-venous ECMO was associated with hospital mortality (p < 0.001; R ² = 0.80). Patient age (b = 0.053; p = 0.01) and maximum cannula size during treatment (b = -0.075; p = 0.008) were also independently associated with mortality. Studies reporting H1N1 patients presented inferior hospital mortality (24.8 vs 40.6%; p = 0.027). Complication rate was 40.2% (CI 95% = 25.8-56.5), being bleeding the most frequent 29.3% (CI 95% = 20.8-39.6). Mortality due to complications was 6.9% (CI 95% = 4.1-11.2). Mechanical complications were present in 10.9% of cases (CI 95% = 4.7-23.5), being oxygenator failure the most prevalent (12.8%; CI 95% = 7.1-21.7). Despite initial severity, significant portion of patients treated with veno-venous ECMO survive hospital discharge. Patient age, H1N1-ARDS and cannula size are independently associated with hospital mortality. Combined effect of patient age, year of study realization, MV days and prone positioning before veno-venous ECMO influence patient outcome, and although medical complications are frequent, their impact on mortality is limited.

Keywords: Acute respiratory failure (ARF); Extracorporeal CO2 removal (ECCO2R); Extracorporeal bypass; Extracorporeal life support (ECLS); H1N1; Mechanical ventilation.

Fig. 1

Consort chart of included/excluded studies

Fig. 2

Funnel plot of included studies. White circles represent observed studies. Mean point was computed using a random effects model and is presented as white rhomboid. Using the Trim and Fill method, one additional imputable study was identified. The estimated corrected mean point with confidence interval is presented as a black rhomboid

Fig. 3

Forest plot—hospital mortality