Predictors of Mortality in Patients With Refractory Cardiac Arrest Supported With VA-ECMO: A Systematic Review and a Meta-Analysis

Cardiac arrest (CA) is associated with high mortality rate, ranging between 75% and 93%. Given its significance, venoarterial extracorporeal membrane oxygenation (VA-ECMO) has been used for end-organs perfusion and to maintain adequate oxygenation as a life-saving option in refractory CA. The predictors for the success of VA-ECMO in this setting have not been established yet. In this meta-analysis, we aim to identify the variables associated with increased mortality in patients with CA supported with VA-ECMO. We conducted a systematic review and meta-analysis to evaluate mortality-predicting factors in patients with CA supported with VA-ECMO that were published between January 2000 and July 2022. To identify relevant articles, the MEDLINE (Pubmed, Ovid) and Cochrane Databases were queried with various combinations of our prespecified keywords, including VA-ECMO, CA, and mortality predictors. We performed a meta-analysis using a random-effects model to calculate the odds ratio (OR). We retrieved a total of 4476 records, out of which we included 10 observational studies in our study. A total of 931 patients were included in our study with the age range of 47-68 years, predominantly males (63.9%). The overall mortality was 69.4%. The predictors for mortality were age >65 (OR 4.61, 95% CI 1.63-13.03, P < 0.01), history of chronic kidney disease (OR 2.42, 95% CI 1.37-4.28, P < 0.01), cardiopulmonary resuscitation duration prior to ECMO > 40 minutes (OR 6.62 [95% CI 1.39, 9.02], P < 0.01), having an initial nonshockable rhythm (OR 2.62 [95% CI 1.85, 3.70], P < 0.01) and sequential organ failure assessment score >14 (OR 12.29, 95% CI 2.71-55.74, P <0.01). Regarding blood work, an increase in lactate by 5 mmol/L increased the odds of mortality by 121% (2 studies; OR 2.21 [95% CI 1.26, 3.86], P < 0.01; I2 = 0%) while the increase in lactate by 1 mmol/L increases odd of mortality by 15% (2 studies, OR 1.15 [95% CI 1.02, 1.31], P = 0.03, I = 0%), and an increase in creatinine by 1 mg/dL increased the odds of mortality by 225% (1 study; OR 3.25 [95% CI 1.22, 8.7], P = 0.02). Albumin was protective as for each 1 g/dL increase, the odds of mortality decreased by 68% (1 study; OR 0.32 [95% CI 0.14, 0.74], P < 0.01). Refractory CA requiring VA-ECMO has a high mortality. Predictors of mortality include age >65, history of chronic kidney disease, cardiopulmonary resuscitation duration prior to ECMO > 40 minutes, initial rhythm being non-shockable and Sequential Organ Failure Assessment score >14.