Did you know few flight programs carry a mechanical compression device? When I first discovered this I found it interesting that an entity that transfers the sickest of the sick - has to provide manual or no chest compressions while flying if a patient arrests. I started asking people within the industry what their guidelines were and the standard response was:
Why would you ever fly a patient in cardiac arrest?
There are essentially two types of patient who I fly in cardiac arrest. For the sake of this blog, I want to focus on why I believe in certain circumstances, the refractory vfib/vtach should be flown to an ECMO capable facility. Yes, taking a patient without a pulse, and flying them with ongoing CPR.
Recently The Lancet published the first ECMO randomized control trial. This was a phase 2, single-center, open-label, pragmatic, randomized clinical trial. This study enrolled patients (ages 18-75) who presented with vfib/vtach out of hospital cardiac arrest (OHCA), remained in vfib/vtach despite three shocks, and transport time to an ECMO capable facility was estimated to be less than 30 minutes. The transporting EMS program also needed to have the ability to provide mechanical compressions in transport (safety first).
Once the patient arrived to the hospital they would be randomized to either standard ACLS or ECMO. A gas would be drawn in the patients randomized to ECMO and if at least two of the parameters listed below were found, the patient would not qualify for ECMO.
Before I show you the results, I want to take a slight deviation and point out that the majority of patients who survive cardiac arrest get ROSC within the first three shocks. For each shock that is delivered, the chance of 30 day survival decreases (Holmén et al., 2017).
The reason I am showing you this is because the patient population included in this study starts after the three shocks. These are patients that are typically pronounced where we find them. Eventually, whatever rhythm they were in terminates to asystole and we make that call to medical control. This is an important distinction to make because “stay and play“ drastically meets diminishing returns after three shocks. ECMO may give this cohort a shot and is why this population was chosen for the ARREST trial.
Ok, now let's look at the results!
Out of the group that was randomized to standard ACLS, only one person survived to discharged and did not survive past the 6 month mark. In the ECMO group there was a 43% survival rate that extended to 6 months. These are patients that statistically would have had a very small chance of survival.
The mean time from 911 call to ECMO was 59 minutes. While I know not everyone has an ECMO capable facility within 30 minutes, the use of air medical resources may expand that possibility in some parts of the country. The trick is to identify when the trigger to request HEMS should be initiated. If EMS waits until the third shock to call for a helicopter, the window of opportunity may start to diminish. I don't have the answer to this but as we typically say in HEMS, put us on standby if needed.
The logistics of prolonged resuscitation to ECMO
You need to be secured in your seat and still provide high quality CPR. In the transport setting this is done with mechanical CPR.
Oxygenation and ventilation can likely take a back seat in the first 5-10 minutes of adult resuscitation. I have seen programs that drop an oral airway, place a non-rebreather, and just do compressions for the first X amount of minutes. I think this is probably ok most the time, but when you are seeing resuscitation times of 30-50 minutes, the patient is in a metabolic phase of arrest (Weisfeldt, 2002) and oxygenation/ventilation become increasingly more important. I think this is probably best done with a mechanical ventilator as opposed to a bag valve mask. The pressure/flow trigger will need to be turned off and pressure titrated to appropriate VTE (I'll probably do a whole blog on this soon).
Epi is best used early and loses benefit in the later phases of cardiac arrest. If patient are identified as an ECMO candidate, this studies protocol recommended no more than 3 mg.
There is likely a role for transesophageal ultrasound to eliminate the need for rhythm checks. Some monitors will also allow you to see through the compression artifact to identify the underlying rhythm.
Closing Thoughts
While remaining on scene and working a cardiac arrest for an arbitrary time may be your local guidelines, there are a subset of patients that will benefit from ECMO if available. I believe air medical resources can help facilitate this in areas where ground transport will take longer than 30 minutes.
On Thursday (3/18) I will be giving a talk on this topic for the Stryker Cardiac Resuscitation Symposium. If you are interested in learning more about this topic, I recommend you sign up while seats are available. Here is the link.
References:
Holmén J, Hollenberg J, Claesson A, Herrera MJ, Azeli Y, Herlitz J, Axelsson C. Survival in ventricular fibrillation with emphasis on the number of defibrillations in relation to other factors at resuscitation. Resuscitation. 2017 Apr;113:33-38. doi: 10.1016/j.resuscitation.2017.01.006. Epub 2017 Jan 18. PMID: 28109996.
Weisfeldt ML, Becker LB. Resuscitation After Cardiac Arrest: A 3-Phase Time-Sensitive Model. JAMA.2002;288(23):3035–3038. doi:10.1001/jama.288.23.3035
Yannopoulos D, Bartos J, Raveendran G, Walser E, 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 Nov 12:S0140-6736(20)32338-2. doi: 10.1016/S0140-6736(20)32338-2.
