Survival rates with good neurological outcome from out-of-hospital cardiac arrest remain low despite public cardiopulmonary resuscitation (CPR) education, public access defibrillators, and advances in emergency medical services. High quality CPR and early defibrillation are critical for success. Many patients who still have potential for good outcomes, however, do not respond to standard resuscitation techniques. Rapid restoration of circulation by implementation of extracorporeal CPR (ECPR) could rapidly provide perfusion and oxygenation to the brain and other vital organs to allow recovery. Minimizing the time from the patient’s collapse to restoration of good perfusion with ECPR is critical for improving the patient’s chances for a good outcome.1 Once initiated, ECPR can be used for prolonged support if necessary until stable, spontaneous circulation can be restored.

Many hospitals have developed systems for implementing ECPR for cases of refractory in-hospital or out-of-hospital cardiac arrest. Improvements in the technology for ECPR have facilitated more rapid initiation. In addition, many non-surgeons have learned how to cannulate, thus increasing the availability of trained personnel for rapid initiation.2

For patients who suffer a refractory cardiac arrest outside the hospital, continuing standard Advanced Cardiac Life Support (ACLS) or rapid transport to a facility that has ECPR available in the Emergency Department are typically the only options. In this issue of Resuscitation, however, Lamhaut and colleagues, from the Service d’Aide Me?dicale Urgente (SAMU) in Paris, report on their growing experience with taking ECPR outside the hospital.3

Developing a system to initiate ECPR inside the hospital is extremely challenging. Which patients should be eligible? Who should cannulate? Which equipment should be used and who will set it up? Few hospitals have such a system in place. Taking this technique outside the hospital is orders of magnitude more difficult. The providers need to learn how to cannulate the patient and prepare the extracorporeal circuit without the additional assistance and equipment that is available in the hospital.

To manage patients suffering refractory cardiac arrest, the SAMU have developed a 2-tiered response. The first tier consisted of a mobile intensive care unit (MoICU) team (1?2 emergency physicians, one nurse, and one-paramedic). If this team felt that the patient has refractory cardiac arrest and was eligible for ECPR, they alerted the second tier team, known as the pre-hospital extracorporeal life support (PH-ECLS) team, which included two senior emergency physicians and/or an intensivist, one nurse, one paramedic and one logistician. These team members have received special training in the management of ECLS from experts in intensive care and cardiac surgery. Cannulation was performed using a cutdown on the femoral vessels and direct cannulation of the vessels using a Seldinger technique. Transthoracic echocardiography was used to confirm the position of the venous cannula tip.

The financial costs and manpower necessary to create a successful ECPR system, as well as the high risk of the intervention, makes careful selection of patients imperative. In their initial feasibility study, previously reported in Resuscitation, the SAMU group used the following inclusion criteria: (1) witnessed cardiac arrest, (2) CPR initiated within 5?min of arrest, (3) PH-ECLS team available, (4) absence of severe comorbidities, (5) cardiac arrest not due to toxic causes or hypothermia, and (6) age <70 years.4 Patients had to have had signs of life during ACLS. Cardiac arrest was considered refractory if restoration of spontaneous circulation (ROSC) had not occurred by 30?min. After gaining more experience with the technique, the group changed the inclusion parameters to reduce the delays in initiation of ECPR. In the new strategy, (1) refractory cardiac arrest was determined after only 20?min of ACLS, (2) anticipated initiation of ECPR within 60?min of arrest, (3) limited epinephrine administration, and (4) earlier dispatch of the PH-ECLS team (simultaneously with dispatch of the MoICU team). The authors found that their new approach was associated with a shorter duration of ACLS prior to initiation of ECPR and improved survival by both multivariate analysis and propensity scoring. Although others have suggested that ECPR initiated in the Emergency Department could improve outcomes for patients with refractory out-of-hospital cardiac arrest,5 this is the first series of patients for whom ECPR was initiated outside the hospital.

This study does have important limitations. First, improved outcomes over time may have occurred because the teams have become more experienced, not because the criteria were more appropriate. Second, the authors chose a very select patient population for enrollment, limiting the potential generalizability of the results. Third, unlike most systems in the world, the SAMU deploys highly specialized physicians to manage the patient from the beginning, further limiting generalizability.

Most importantly, the study did not directly compare the patients who received ECPR outside the hospital with those who never received ECPR. They did explore the results of initiation of ECPR outside the hospital with initiation once the patient arrived at the hospital, but this comparison is fraught with selection and survival bias; the criteria for initiating ECPR outside the hospital were relatively arbitrary. As the authors point out, a randomized study is needed.

Choosing the most appropriate patients for a high-risk intervention, such as ECPR, can be quite difficult, particularly because decisions must be made within minutes, usually with very little information. The new criteria, studied in the current paper, mainly affects the time from onset of cardiac arrest to initiation of ECPR. In that regard, the risk for initiating ECPR too early is that one may not give standard care a fair chance for success, leading to enrolling patients who would actually have done well anyway. On the other hand, waiting too long could doom the intervention to failure.5, 6 The attempts by this group to better define the best criteria for out-of-hospital implementation of ECPR are commendable.

This study has important implications for more widespread use of ECPR for patients with refractory cardiac arrest, whether in the hospital or outside the hospital. Like previous in-hospital studies, the authors have demonstrated that non-surgeons, with the right training, can safely implement ECPR.2 Further, with the right equipment and a small team of trained assistants, these physicians can implement ECPR outside the hospital and transport the patients safely.

Appropriately implementing new procedures and new technology during resuscitation of a patient in cardiac arrest is particularly challenging. Except for a couple of case reports, the current study is the first to report on a series of patients who underwent ECPR outside the hospital. The increasing success rate for ECPR demonstrated here using more stringent patient enrollment criteria is a testimony to the great potential of ECPR to save the lives of patients who suffer refractory cardiac arrest.

The SAMU group has paved the way by demonstrating the feasibility for initiating ECPR outside the hospital. The question is where to go from here. The authors have initiated a randomized clinical study of ECPR (NCT02527031), which will undoubtedly increase our understanding of the utility of out-of-hospital ECPR. Hopefully, other groups will follow suit and help push this novel approach forward and help better define the right patient selection and the right techniques for implementing ECPR outside the hospital. Though we’re not ready to routinely take ECPR to the patient, wherever that may be, we are one stop closer to determining how and when to take ECPR outside the hospital.

Conflict of interest statement

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