Episode 38- ECMO for out-of-hospital cardiac arrest: Is this the future?

Hello and welcome to Episode 38 of ER-Rx. This week, we review a recently-published study entitled “The Minnesota mobile extracorporeal cardiopulmonary resuscitation consortium for treatment of out-of-hospital refractory ventricular fibrillation.” This study describes a potentially game-changing intervention for patients with out-of-hospital cardiac arrest (OHCA): extracorporeal CPR (ECPR) using ECMO.

OHCA affects over 350,000 patients every year in the United States, with a survival rate of < 10%. Although patients presenting with shockable rhythms (such as VF, pVT) have better outcomes (~ 30% survival rates), about half of these patients are refractory to standard ACLS measures. We talked about this in Episode 21 (Esmolol in refractory VF arrest) and Episode 33 (Shock through the heart: is two better than one?). Refractory VF/pVT is most commonly associated with severe coronary artery disease (CAD) with occlusion, with horrible survival rates if this occlusion is not immediately reversed. If only we could keep patients alive until we were able to reverse these occlusions… Enter ECPR with ECMO.

ECMO is a technique that provides cardiac and respiratory support by drawing blood out of the body, artificially oxygenating it, then returning the blood to the patient. It comes in two flavors; veno-venous (VV) or veno-arterial (VA). In VV ECMO, only the lungs are bypassed, with access usually placed in large veins for drainage and infusion. In VA ECMO, both the lungs and the heart are bypassed, and access is placed in a large vein for drainage, with an arterial access point for infusion. ECMO-facilitated resuscitation acts as a bridge, allowing angiography with PCI, optimizing hemodynamics, and supporting multi-organ injury and recovery of the heart after cardiac arrest.

ECMO followed by immediate coronary angiography and intervention has been used in small trials to treat refractory VF/ pVT. This particular study builds on past case series and the authors’ previously reported single-center “ARREST” trial, which was the first randomized trial of ECMO in cardiac arrest in the United States. The “ARREST” trial showed a 43% survival rate with ECMO compared to only 7% with standard ACLS measures. The effects were so great that the study was stopped early due to the high survival rates in the ECMO group.

Given the success of the “ARREST” trial, the authors of this study wanted to determine if the ECMO approach could be provided outside of a single center. This observational study described the implementation and reported outcomes from the first OHCA, ECMO-facilitated program in the United States. This ECMO program consisted of mobile ECMO cannulation teams, 3 ECMO initiation hospitals (which actually included my site), 24/7 cath lab availability, and a single ECMO ICU post-cannulation. The cannulating physicians were specialists from interventional cardiology, emergency medicine, and critical care.

This study included a period between December 2019 and April 2020. Patients were transported by EMS to the nearest ECMO initiation hospital’s ER if they; were adults (aged 18-75), had VF/pVT OHCA, were receiving CPR with a LUCAS, had no ROSC after 3 shock attempts, and had an estimated transfer time of < 30 minutes. Patients were excluded if they were DNR, had massive bleeding, or had a known terminal illness.

Once a patient was deemed eligible, paramedics would call a central dispatcher who notified the mobile ECMO team and ECMO site. This is when the fun started; ER techs would frantically work to set up a trauma room so that it would be conducive to ECMO cannulation, nurses would set up fluids bags and get iStats ready, and the pharmacist would pull all the meds (including standard ACLS meds like epi and bicarb, but also heparin for post-cannulation use).

Once the patient arrived to the ER, a blood gas and lactic acid were measured to determine if resuscitation would be continued. Patients who had two or more of; an end-tidal CO2 /= 18 mmol/L were deemed unlikely to benefit and were declared dead. Patients without these criteria underwent emergent ECMO cannulation while the ER team continued resuscitation. Next, the patients were transported to the CT scanner to assess for CPR-related trauma. After that, they went to the cath lab for intervention as needed. Finally, they were transported to the centralized ECMO ICU for ongoing cares including therapeutic hypothermia.

In the end, 58 patients met criteria (~14.5 per month). Of those, 13 (22%) met the resuscitation discontinuation criteria and were pronounced dead, leaving 45 patients (78%) that received ECMO cannulation and cath lab intervention. Of those, 4 patients (7%) were declared dead prior to transfer to the ECMO ICU, leaving 41/58 patients (71%) that were eventually transported to the ECMO ICU. The mean age was 57 years, > 80% were white, and known comorbidities of CAD was seen in 30% of patients. Mean response time of the ECMO team was 15 minutes, mean time from patient arrival to ECMO initiation was also 15 minutes, and all cannulations were successful. In the cath lab, 29/45 patients (64%) had severe CAD and of those, 22/29 patients (85%) received PCI.

The results were astounding. Functionally favorable survival (defined as cerebral performance category [CPC] scores of 1 or 2) occurred in 25/58 (43%) of patients. The survivors’ mean hospital LOS was 19 days, 80% were discharged to acute rehab facilities, and all of them were still alive at 3 months.

In conclusion, the authors stated that ECMO-facilitated resuscitation programs have the potential to transform outcomes for this patient population. The authors recognize that the success of the program is dependent on a high level of involvement from multiple healthcare systems, EMS services, and staff. They also admit that this intervention is very resource intensive and requires extensive education and training of everyone involved. Nevertheless, with such high survival rates shown in this study, the previous “ARREST” trial, and other small case series and case reports, this may be a model for the future.

As always, thank you so much for your time. If you would like more information about our own ECMO experience or the specific roles of the ER pharmacist during an ECMO activation, please reach out to me on errxpodcast.com or the errxpodcast Instagram page.