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The Edge: Is It Time to Rethink Cardiac Arrest Care?
The Edge is a monthly blog series developed by EMS World and FlightBridgeED that features top EMS medical directors exploring the intricacies of critical care in EMS practice. In this installment the associate medical director of FlightBridgeED’s Podcast Division, Ritu Sahni, MD, discusses advances in cardiac arrest care.
Cardiac arrest care has made some significant steps forward in the last 10–15 years. The emphasis on CPR quality has laid a foundation for improving outcomes, both in numbers of survivors as well as neurologic outcomes. At first glance it appears things are moving in the right direction.
However, when one looks more closely at the numbers, are we really making a difference? The 2020 CARES Annual Report identified that just 9.5% of cardiac arrest patients survived to hospital discharge last year.1 And although COVID played a role in survival, there really has been little change in CARES outcome data over the last few years. So, this prompts the question: Is it time to change our approach to cardiac arrest?
ECMO CPR: Game-Changer?
Extracorporeal membrane oxygenation, or ECMO, has long been used in the ICU setting to manage critical patients with acute respiratory distress syndrome as well acute cardiogenic shock. ECMO is best described as a version of heart-lung bypass, but instead of cannulation occurring at the heart after a thoracotomy, it occurs at the femoral site. Additionally, ECMO technology is designed to support the patient for days to weeks instead of just during a surgical case.
The technology and concepts are not new, but recent advances have made it much more accessible. Most important, the ECMO “machine,” which used to basically be full-size and table-length, has now been reduced to roughly the size of a football. This has implications for use of ECMO in the ED and possibly even the field. The biggest challenges are that 1) placing patients on an ECMO machine requires a specific set of skills, and 2) patients need to be maintained in a specialized ICU with experience caring for these patients. So while there have been significant breakthroughs, there is still significant cost and a set of specialized skills required—which means accessibility will always be a problem.
We have been hearing this for years. So what has changed? Data!
EMS is well known for adopting technology and “toys” potentially before their time. ECMO may be no different, as there are ECMO-CPR (sometimes called ECPR or ECLS) programs in existence. Now we also have the ARREST trial.2 This randomized, controlled trial compared standard cardiac arrest care to ECMO in out-of-hospital cardiac arrest patients who had initial shockable rhythms refractory to three shocks.
OHCA patients with transport times less than 30 minutes who did not convert after three shocks were immediately transported to the participating ECMO center, maintained on a LUCAS device during transport. At the ED they were randomized to either an intervention group or a standard care group. It is important to note those randomized to standard care had to have their arrest care continued for at least 15 minutes before the resuscitation could be called. The intervention group went to the cardiac catheterization lab, where femoral arterial and venous cannulation occurred, and patients were placed on ECMO. This was followed by a cardiac catheterization/angiogram and intervention if indicated. The initial plan was to enroll 150 patients.
Results
When looking at the results, the first thing that stands out is that there were only 15 patients per group. Why so few? This study was performed under exception from informed consent (EFIC). EFIC studies are meant to evaluate emergency situations in which obtaining consent is impossible due to a combination of patient condition and timeliness. Part of the safety/monitoring of an EFIC study includes intermittent analysis by an independent data safety monitoring board (DSMB). The DSMB monitors the study data for any compelling reasons to halt the study. In this study the DSMB reviewed the data at a planned interval of 30 enrollments. It found the difference in survival between the two groups was so large (i.e., the intervention worked so well) that it would be unethical to continue the study. Instead the study ended, and the authors started reporting the results.
What were the results? Survival in the ECPR group was 43% vs. only 7% for the standard care group. Another way to look at this would be that the number needed to treat (NNT) to save one person was 3. There are very few interventions in all of medicine with NNTs this low. As an example, the NNT for percutaneous intervention for STEMI is about 17.3 Additionally, the ECMO patients had better long-term survival and better neurological outcomes.2
What about elsewhere? Recently a study from Prague was presented at the American College of Cardiology meeting.4 This study, which has not yet been peer-reviewed, enrolled 256 patients. The authors found a six-month survival of 35%, compared to only 22% in their standard care group. Not quite as huge a difference as the ARREST trial, but still quite large. This would imply that similar systems of care can work in other settings.
What About EMS?
Having one ECMO center in a metropolitan area does somewhat limit its availability to a small number of potential arrest patients. What are the strategies to develop wider availability? There are two recently published: 1) Bring ECMO to the community hospital (as has recently happened in Minnesota) or 2) perform ECMO in the field (as has been done in Paris and now Albuquerque).
While the ARREST trial was taking place, Minneapolis-area leaders trialed the creation of the Minnesota Mobile Resuscitation Consortium.5 In this regional pilot project, three regional hospitals were identified as ECMO initiation hospitals. If a cardiac arrest occurred that was refractory VF/VT, the patient was transported to one of these centers. At the same time, an ECMO cannulation team was dispatched to the hospital. The cannulation team then started ECMO in the emergency department. The patient went to the cardiac catheterization lab at the initiation site, and interventions were performed as indicated. Finally, the patient was then transferred to the ECMO ICU at the same site as the ARREST trial.
This cohort, which was not part of a study, had a survival of 47%. This again far exceeded historical survival for refractory VF/VT. There were 41 patients in this group.
In the Albuquerque model cannulation is dispatched directly to the scene and occurs at the location in the back of special ECMO ambulance. The ambulance and team respond from the hospital and transport the patient back to the ECMO receiving center. At this time leaders only have case reports describing their interventions, but they are convinced this proof of concept works.6
What It Means
There appear to be about 360,000 cardiac arrests annually.7 With incremental change and improvements, we have more survivors with better neurologic outcomes than ever before.1 However, taking a step back and looking at the whole, we have basically been making minor alterations to a model that has existed for decades. Perhaps it’s time to look at a new method for significantly increasing survival in a subset of our patients. It will require the further creation of integrated systems of care—but that is what EMS does best.
References
1. Cardiac Arrest Registry to Enhance Survival. 2020 Annual Report, https://mycares.net/sitepages/uploads/2021/2020_flipbook.
2. Yannopoulos D, et al., Advanced reperfusion strategies for patients with out-of-hospital cardiac arrest and refractory ventricular fibrillation (ARREST): a phase 2, single centre, open-label, randomised controlled trial. Lancet, 2020; 396(10,265): 1,807–16.
3. Andersen HR, et al. A Comparison of Coronary Angioplasty with Fibrinolytic Therapy in Acute Myocardial Infarction. New Eng J Med, 2003; 349(8): 733–42.
4. American College of Cardiology. ‘Hyperinvasive’ Care Improves Survival in Refractory Out-of-Hospital Cardiac Arrest, 2021 May 17; www.acc.org/about-acc/press-releases/2021/05/17/04/23/hyperinvasive-care-improves-survival-in-refractory-out-of-hospital-cardiac-arrest.
5. Bartos JA, et al. The Minnesota mobile extracorporeal cardiopulmonary resuscitation consortium for treatment of out-of-hospital refractory ventricular fibrillation: Program description, performance, and outcomes. EClinicalMedicine, 2020 Nov 13; 29–30: 100632.
6. Marinaro J, et al. Out-of-hospital extracorporeal membrane oxygenation cannulation for refractory ventricular fibrillation: A case report. J Am Coll Emerg Physicians Open, 2020; 1(3): 153–7.
7. Becker LB, Aufderheide TP, Graham R. Strategies to Improve Survival From Cardiac Arrest: A Report From the Institute of Medicine. JAMA, 2015; 314(3): 223–4.
Ritu Sahni, MD, MPH, FAEMS, is associate medical director of the Podcast Division and cohost of the SecondShift podcast for FlightBridgeED.
