Out-of-hospital cardiac arrest ( OHCA ) is a highly lethal emergency, unless return of spontaneous circulation ( ROSC ) is timely achieved by efficient and effective resuscitation. Nevertheless, despite advanced cardiopulmonary resuscitation ( CPR ) with mechanical chest compression, assisted ventilation and automatic external defibrillation, the survival of OHCA patients remains below 10%. Extracorporeal membranous oxygenation ( ECMO ) facilitated life support ( ECLS ) could help hemodynamic stability and improve significantly the survival of refractory OHCA to 25-40 %. On the other hand, the precise role and timing of the ECLS during the emergency management of OHCA remains largely unestablished.

In the present study, we hypothesized that emergency total ECLS is superior to standard ACLS with ECMO bailout for survival with favorable neurological outcome in refractory out-of-hospital cardiac arrest. All OHCA patients meeting the including criteria, i.e. age 18-75 years, witnessed cardiac arrest with bystander CPR, initial shockable rhythm as ventricular fibrillation or pulseless ventricular tachycardia ( VF/pVT ), repeated defibrillation shocks and escorted transportation within 30 minutes from 119 call to arriving emergency department ( ED ) in the hospital would be recruited. Eligible patients will be consecutively randomized at ED in 1:1 ratio, stratified by hospitals, into emergency total ECLS group and standard ACLS with ECMO bailout group. Informed consent is waived in the life-threatening emergency condition. For emergency total ECLS group, OHCA patients will receive early implantation and initiation of ECMO circulation within 15 minutes after randomization or up to 45 minutes after 119 call. For standard ACLS with ECMO bailout group, OHCA patients will receive standard ACLS for at least 45 minutes after collapse or 119 call or at least 15 minutes after ED arrival before calling for bailout ECMO if required. Following return of spontaneous systemic circulation (ROSC) or depending on ECMO circulation, both groups would be transferred to brain and chest computer tomography screening, emergency coronary revascularization intervention and subsequent intensive cardiac care with targeted hypothermia management. Survivals will be treated with guideline directed medical therapy for reduced ejection fraction heart failure and/or implantable cardioverter-defibrillator implantation for prevention of recurrent VT/VF in wards. All survivals will be followed up for medical and neurological status at 30 days, 90 days and 180 days after discharge.

Primary endpoint is survival with favorable neurological outcome at 30 days. Secondary endpoints are survival to discharge with favorable neurological outcome, survival with favorable neurological outcome at 180 days, total duration of cardiopulmonary resuscitation ( CPR ), total duration of mechanical ventilation, total duration of intensive care unit stay, total duration of hospitalization. Safety endpoints will be incidence of serious adverse events related to prolonged CPR, prolonged ischemia, and ECMO systemic perfusion and coronary reperfusion.

The number of subjects to be enrolled according to the primary endpoint of 30 days survival with favorable neurological outcome. With a power of 80%, accepting the level of statistical significance at alpha= 0.05 and based on two-sided Chi-Square test, we estimated 166 participants per arm are needed. This is based on the 30% success rate and 15% success rate of 30-day survival with good neurological outcome of emergency total ECLS intervention and standard ACLS with bailout ECMO (if required) intervention, according to previous trials, plus a 10% drop out rate. Based on two-tailed test, p less than 0.05 is considered statistical significance. If interim analysis is deemed necessary, the significance level will be adjusted accordingly using Bonferroni method. Because of no interim analysis and no stopping point in ITT protocol, there is no criteria for premature termination of the trial. The missing data of the primary and secondary efficacy outcomes will be considered as failure for ITT analysis. Last observations carry forward method will be adapted for the missing data of repeated measurements. The data record will be monitored and audited by the Institutional Review Board of the TMU Shuangho hospital as well as the Data and Safety Monitoring Plan committee.