Initial pH and shockable rhythm are associated with favorable neurological outcome in cardiac arrest patients resuscitated with extracorporeal cardiopulmonary resuscitation

Refractory cardiac arrest, usually defined as persistent cardiac arrest despite 30 minutes of medical cardio-pulmonary resuscitation (CPR) (1), is associated with an extremely low probability of survival with conventional CPR. In this setting, extracorporeal CPR with veno-arterial extracorporeal membrane oxygenation (ECMO) has been found to be associated with better neurological outcome compared to conventional CPR (2-4). A recent analysis of the Extracorporeal Life Support Organization (ELSO) database showed that the use of extracorporeal CPR (eCPR) has increased during the last decade (5). Because no prospective randomized trial is available, there is currently no strong recommendation that precisely details the exact indications for eCPR. Indeed, the guidelines of the European Research Council of 2015 only stated that eCPR should be considered as a rescue therapy for patients in whom initial advanced life support measures are unsuccessful (6). Because eCPR is associated with a very high mortality rate, identification of early prognostic factors is needed for avoiding futile care. In the setting of out of hospital cardiac arrest (OHCA), a recent metanalysis has identified initial shockable rhythm, low flow duration, pH and lactate values as prognostic factors (7). In the setting of in-hospital cardiac arrest (IHCA), initial shockable rhythm, low flow duration, lactate, creatinine and Sequential Organ Failure Assessment (SOFA) have been found to be associated with outcome (8). While such factors obviously reflect severity, data regarding to critical thresholds are lacking