For an adult suffering from a medical cardiac arrest, the chance of a neurologically intact outcome after 20 minutes of resuscitation is essentially zero. As a result, some hospitals have begun to incorporate extracorporeal membrane oxygenation (ECMO) into cardiac arrest resuscitation, which is then known as ECPR. ECPR carries a Level IIb recommendation from the AHA. Patients who are considered ECPR candidates are generally placed on ECMO after 20 minutes of failed conventional resuscitation but before 60 minutes of total downtime (presuming they had good CPR that entire time) in order to have a reasonable chance of neurologically intact survival.
The goal of ECPR is to maintain end-organ perfusion while allowing reversible causes of cardiac arrest—such as a coronary occlusion—to be corrected. This is typically achieved by placing a large cannula (up to 29-French) in a femoral vein to remove blood from the body, passing it through a pump that forces the blood through a membrane that adds oxygen and removes CO2 before sending it back into a large cannula (up to 21-French) in a femoral artery with enough pressure to perfuse the brain and body. This is then referred to as venoarterial ECMO.
ECPR is generally restricted to a limited number of tertiary care centers. Since patients must arrive at the center with adequate time to undergo the cannulation procedure and still go “on pump” within 60 minutes of initial collapse, only a limited number of patients are candidates. One potential solution is to take ECPR to the patients. Prehospital ECMO (PECMO) has been utilized in Paris since 2011 and is now being implemented in various other countries, including Australia, Spain, and the U.K. Although the use of ECPR for patients who suffer cardiac arrest in the hospital has been available in some U.S. centers for many years, there have been no cases to date of PECMO in the U.S.
Many Unique Systems
Metropolitan Albuquerque, N.M., is home to approximately 900,000 people and covers approximately 190 square miles. There are nearly 600 out-of-hospital cardiac arrest cases annually in the Albuquerque metropolitan area, but few of these patients are close enough to University of New Mexico Hospital (UNMH) to be transported by EMS and still considered candidates specifically for ECPR. At UNMH the use of ECMO has conferred excellent survival rates for patients in cardiac arrest, with more than 30% last year surviving to hospital discharge with good neurological outcome. In conjunction with the Center of Adult Critical Care at UNMH, EMS physicians from the UNM Department of Emergency Medicine EMS Consortium recognized the importance of implementing PECMO to provide this technology to patients living in geographically distant areas that preclude transport to the hospital in OHCA.
This team of UNM physicians worked closely with Albuquerque Fire Rescue (AFR) leadership to establish our PECMO program in the summer of 2019, with the first case occurring in October 2019. The implementation of PECMO requires many unique systems to be in place, all of which exist in Albuquerque.
These include a high-performance EMS system that already provides high-quality cardiac arrest resuscitation; inspired leadership and providers who are open to new ideas; a physician field-response program (we have 10 faculty and fellow EMS physicians who routinely attend 30% of OHCA calls in the city); a close relationship between EMS and the receiving hospital; a functional hospital-based ECPR program; and physicians to perform the ECMO cannulation procedures who are able and willing to both take calls and go out into the field. We are particularly fortunate to have a large group of emergency physicians that have completed critical care fellowship training and perform the vast majority of ECMO cannulations in our facility, along with one supportive vascular surgeon.
Our PECMO team consists of three senior critical care physicians who serve as the cannulators, three specially trained UNM EMS physicians (including the AFR medical director), the AFR paramedic supervisor from each of our three AFR shifts, and firefighter-paramedics from AFR Station 3 located on the UNM campus. These firefighter-paramedics were uniquely trained to function as first assistants during EMCO procedures, staying within the state scope of practice but providing essential support. A retired AFR ambulance unit was converted into an advanced cardiac resuscitation unit, call sign ECMO-1, stocked with all the supplies and equipment necessary for PECMO and kept at AFR Station 3.
The uniformed communication specialists in our AFR dispatch center were trained to recognize potential ECPR candidates at the time of dispatch. For a patient to be eligible for PECMO, they must be between 18–75 years old. Importantly, they must have a witnessed arrest with bystander CPR within five minutes. The initial rhythm can be ventricular fibrillation, ventricular tachycardia, or pulseless electrical activity. Additionally, if the patient is shocked from one of the three presenting inclusion rhythms into asystole, they remain a candidate for PECMO. Exclusion criteria include asystole as the presenting rhythm and comorbid conditions including chronic kidney disease, liver or lung disease, cancer, and obvious trauma.
How It Works
The dispatch center alerts crews to a potential ECPR patient at the time of dispatch for any adult cardiac arrest. During weekdays from 8 a.m. to 5 p.m. when the entire PECMO team is available, ECMO-1 and an EMS physician are dispatched along with the nearest responding district crews and an AFR paramedic supervisory captain. ECMO-1 proceeds to UNMH hospital to pick up the on-call cannulators on their way to the scene. While en route the cannulators and AFR personnel establish a mini-operating room and don sterile surgical garb. All responding EMS physicians and AFR paramedic captains carry point-of-care ultrasound devices and can perform cardiac ultrasound; patients with PEA are only considered ECPR candidates if there is meaningful cardiac contractility noted on ultrasound.
An interesting aspect of PECMO in our system is the use of a hand crank and oxygenator to establish and maintain flow on the ECMO pump once the patient is cannulated, rather than a traditional ECMO machine. This avoids the need for a perfusionist or ECMO specialist to be immediately available and allows less-expensive ECMO circuits to be used.
The EMS physician and paramedic supervisor on scene are responsible for ensuring that inclusion and exclusion criteria are evaluated and the family is consented while routine ACLS is administered by the local district AFR units and Albuquerque ambulance crews.
The patient is then stripped from the waist down and has their groin prepped for a sterile procedure with chlorhexidine. CPR is performed with a LUCAS mechanical compression device, and ventilations are carefully delivered with a paraPAC plus ventilator. The patients are then loaded into ECMO-1 feet first, which allows for better patient access. A pop-up tent is placed at the rear of the ambulance to maintain patient privacy and keep the crews protected from the elements.
While the cannulas are placed using ultrasound guidance, routine cardiac resuscitation is continued by the initial on-scene fire and EMS crews from the rear doors of the ambulance, with the addition of routine crystalloid infusions and an epinephrine drip. EMS physicians also administer a heparin bolus to help prevent clotting in the ECMO circuit.
The entire ECMO procedure is performed on-scene and can take over 30 minutes. After the patient is stabilized, they are transported in a nonemergent fashion to UNMH, where they are met in the ED ambulance bay by a perfusionist or ECMO specialist, who transfers the patient onto the Rotaflow ECMO machine before the patient is offloaded and moved into the ED.
Unique, Cost-Effective Model
Since its inception the team has only cannulated two patients, both of whom unfortunately still succumbed to anoxic brain injury. The system worked extremely well, and both patients were on ECMO in less than 60 minutes from collapse. The limited number of patients is secondary to our limited hours of availability and strict inclusion and exclusion criteria.
The capital investment was kept relatively small, but the personnel investment is relatively large on the hospital side as we maintain on-call availability. Fortunately no additional personnel resources are needed from the fire department, though there was a significant amount of upfront training time.
We believe we have developed a unique, cost-effective model for PECMO that will hopefully be replicated and improved upon in other cities that have the interest and requisite infrastructure.
Lauren Bailey, MD, is an EMS fellow at the University of New Mexico.
Kimberly Pruett, MD, is an assistant professor in the Department of Emergency Medicine at the University of New Mexico and medical director for Albuquerque Fire Rescue.
Darren Braude, MD, MPH, FACEP, EMT-P, is a professor of emergency medicine at the University of New Mexico and chief of the division of austere and pre-hospital medicine.