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Traditionally, the use of extracorporeal membrane oxygenation, better known as ECMO, was limited to patients in hospital intensive care units or surgery. However, advances in technology have made available ECMO devices that are compact, portable and cost-effective.
These advancements, coupled with specialized training, have made this once scarce resource more widely available in nontraditional settings. ECMO may be coming to an ED or EMS entity near you, so here are 10 things you should know about ECMO.
1. What is ECMO?
Extracorporeal membrane oxygenation is a life support method in which a pump is used to circulate blood through an oxygenator and back into the patient. ECMO provides normal physiologic levels of blood flow while the heart is stopped. It can provide the perfusion support and extracorporeal gas exchange needed to improve oxygenation to improve cardiac arrest outcomes in out-of-hospital cardiac arrest (OHCA) in selected patients. ECMO has also been called extracorporeal life support (ECLS) or extracorporeal cardiopulmonary resuscitation (ECPR).
Many believe that ECPR can be particularly effective in improving outcomes in many difficult OHCA cases such as drug overdose, pediatric drownings and other difficult-to-resuscitate cardiac arrest scenarios involving pulseless electrical activity.
2. How does ECMO work?
ECMO is a form of cardiopulmonary life support, where blood is basically drained from the vascular system, circulated outside the body by a mechanical pump, oxygenated and then reinfused into the circulation. While the blood is outside the body, hemoglobin in the red blood cells become fully saturated with oxygen and CO2 is removed. [1]
Indications for ECMO can be divided into two main categories: refractory low cardiac output (in the case of case of cardiac arrest and cardiogenic shock) and respiratory support (respiratory failure).
3. What are the two types of ECMO?
There are two types of ECMO – VV (veno-venous) and VA (veno-arterial), which refer to the source and target of blood flow between the two large-bore catheters and the external pump. Most often, the cannulas are inserted into the femoral vessels (artery and vein).
In VA ECMO (heart-lung), used for cardiac failure and cardiac arrest, deoxygenated venous blood from the right atrium is drained by one cannula and passed through an external oxygenator, which serves to oxygenate the blood and remove carbon dioxide. The oxygenated arterial blood is then pumped back into the proximal aorta under pressure by a return cannula in the to complete the circuit.
In VV ECMO, used to support respiratory conditions, the lungs are bypassed and the membrane oxygenator completes the function of the lungs. The patient’s circulatory function is maintained by the system. [2]
4. What is the role of EMS in ECMO?
From the prehospital perspective, ECPR may be considered a high-risk but low-frequency intervention opportunity. ECMO programs have high start-up costs and require specialty resources, so limited patient volumes often place ECMO program quality and financial feasibility at risk. [3] Due to the absence of well-designed ECMO programs, the majority of U.S. healthcare centers only treat one or two patients annually. Only about 20% of U.S facilities that offer ECMO treat more than 10 patients annually.
As these programs grow, however, more EMS agencies will be needed and will need to complete advanced training to transport these critical patients to ECMO facilities. EMS entities have already begun their integration into ECMO programs in Georgia, Utah, California, Ohio and Minnesota. The level of EMS integration into the ECPR interdisciplinary team varies from state to state. What most EMS entities share is an ECPR OHCA protocol that includes well-defined inclusion criteria, exclusion criteria, prehospital resuscitation quality goals and effective communication with the in-hospital ECMO team.
5. How can EMS achieve prehospital integration with hospital ECMO programs?
Across the Atlantic in Paris, EMS can initiate ECMO on scene as part of a prehospital ECMO team. In the Paris system, the medical dispatch center has a physician who screens all calls. The physician then assigns the most appropriate medical response based on the reason of the call and the severity. In cases of OHCA, a mobile intensive care unit (MoICU) travels to the patient. The MoICU team is composed of an emergency physician (anesthesiologist intensivist, cardiologist, etc.), a nurse and a paramedic. The MoICU contains everything a team would need to treat an acute patient in the hospital ED or ICU.
When a cardiac arrest call is received, the local fire department is immediately dispatched along with the MoICU team. Dispatch then continues to guide the witness in bystander CPR over the phone. Upon arrival of the MoICU team, the patient is immediately evaluated to determine if they are a candidate for ECPR while advanced life support care is delivered. If they are an ECPR candidate, the ECPR team is dispatched to the location.
The Paris EMS response system represents the opposite of the “scoop and run” concept. The Paris system has demonstrated that delays in ECPR can be avoided when the appropriate advanced resources (MoICU team, ECPR team, etc.) are sent to the scene and protocols are used to provide early identification of ECPR candidates. (Learn more about the prehospital ECMO program in Paris here and here).
6. What makes a positive patient outcome using ECMO in refractory cardiac arrest?
What does “positive outcome” mean for ECPR with ECMO for patients in OHCA? Is it merely getting the patient to the ED with a pulse, or surviving for three days in the intensive care unit? Generally, studies discuss quality patient outcomes in patients who have positive neurologic outcomes, but many studies fail to define what they measure as a positive neurologic outcome. [4]
The decision to use ECMO in the field should be determined by the agency’s protocol. Unfortunately, protocols vary considerably, as well as the ECPR processes. A 2015 recommendation from the Extracorporeal Life Support Organization suggests that it is medically futile to proceed with ECPR if high-quality CPR has been unsuccessful for 30 minutes. [5] However, the ELSO suggests that if effective CPR is performed with adequate circulatory volume and metabolic support during compressions, and adequate perfusion is provided, ECPR may still be considered.
It is further suggested that the analysis of serial arterial blood gases may be used to measure the effectiveness of CPR in these cases. [5,6] This can be achieved in the field by using a point-of-care test blood gas analyzer. These blood gas results can help prehospital providers achieve the resuscitation quality measures as part of the ECPR team. The respiratory component of acidosis can be treated using appropriate ventilator settings, and the metabolic component can be treated using an exact dose of sodium bicarbonate.
7. What are the challenges to creating integrated prehospital ECPR/ECMO teams?
How likely is it that your EMS agency will be part of a prehospital ECMO team in which ECMO is initiated on scene like the program in Paris? This depends on several complex factors, including the ability of the ECMO program to identify and receive patients in the prehospital setting, the ability to training and maintain the competency of the EMS providers, the ability to integrate EMS into the interdisciplinary team (ED, ICU, cardiac cath lab, etc.), the financial and equipment resources of the EMS agency and more. [7]
Since the procedure is very difficult, it requires the intervention of a physician who would have to be readily available to arrive on scene with EMS. There are other logistical barriers as well, such as purchasing and maintaining supplies, equipment upgrades and maintenance, and detailed coordination of quality data collection and process improvement.
Also, the risk of infection during ECMO initiation is a real concern, even in the most sterile of hospital surgical suites or ICU rooms. What special infection challenges would be anticipated for initiating ECMO on scene or in the ambulance?
8. What is the future of prehospital ECMO?
Although ECPR/ECMO may be a promising procedure to manage OHCA, recovery to discharge requires an effective interdisciplinary team to provide care and long-term follow up. Since many organ systems are affected by interrupted ischemia-reperfusion, a complete post-intensive care management strategy including rehabilitation and secondary prevention measures is vital to sustaining long-term survival benefits. [7, 8, 9, 10] A community paramedicine program can be instrumental as part of the interdisciplinary team.
9. What is EMS’ role in ECMO research?
There is a great need for EMS to be involved in randomized trials to study the use of ECPR in patients with OHCA and in designing and testing ECPR protocols. Although the American Heart Association stated in 2015 that there was insufficient evidence to recommend the routine use of ECPR for patients with cardiac arrest, studies completed since 2015 have reported survival results from 8.8% to 43.5% for ECPR in patients with OHCA and up to 55.6% in patients with V-FibV-Tach OHCA. [9, 11, 12, 13, 14, 15, 16, 17, 18]
Although these results are encouraging, the studies all revealed small sample sizes, were retrospective, observational and without statistical significance. Also, the studies included a wide variety of protocols with large differences in inclusion and exclusion criteria, and differences in in-hospital and prehospital care can account for the wide range of results, making it difficult to evaluate with one’s own EMS service in mind.
10. How can EMS make sense of the wide variability in ECPR with ECMO practices?
Further research is needed to better understand ECPR best practices, such as protocols, inclusion/exclusion criteria and cannulation techniques, as well as the development of formalized hospital, regional and national guidelines for ECPR. Variations in criteria for patient selection, eligibility and contraindications each introduce potential for confounding in clinical research.
ECPR with ECMO in OHCA may show promise in benefiting a select group of patients that require heart-lung support until definitive cardiovascular therapy is obtained. Healthcare partners will need to evaluate how ECMO fits into their cardiovascular strategy and balance its efficacy, growth potential, feasibility and cost of developing a sustainable program. New applications for ECPR with ECMO may present on the horizon. Prehospital providers stand ready to accept their critical role in the interdisciplinary team as this resuscitation science evolves.
References:
1. Schmidt, M., Tachon, G., Devilliers, C., Muller, G., Hekimian, G., Bréchot, N., . . . Combes, A. (2013). Blood oxygenation and decarboxylation determinants during venovenous ECMO for respiratory failure in adults. Intensive Care Medicine, 39(5), 838-846. doi:10.1007/s00134-012-2785-8
2. Stub, D., Bernard, S., Pellegrino, V., Smith, K., Walker, T., Sheldrake, J., . . . Kaye, D. M. (2015). Refractory cardiac arrest treated with mechanical CPR, hypothermia, ECMO and early reperfusion (the CHEER trial). Resuscitation, 86, 88-94. doi:10.1016/j.resuscitation.2014.09.010
3. Tooley, M. & Igmen, A. (2019). ECMO could significantly increase cardiac arrest survival rate. Here’s what you need to know. Retrieved March 15, 2019, from https://www.advisory.com/research/cardiovascular-roundtable/cardiovascular-rounds/2018/03/ecmo-cardiac-arrest
4. Yukawa, Takahiro, et al. “Neurological Outcomes and Duration from Cardiac Arrest to the Initiation of Extracorporeal Membrane Oxygenation in Patients with out-of-Hospital Cardiac Arrest: a Retrospective Study.” Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine, vol. 25, no. 1, 2017, doi:10.1186/s13049-017-0440-7.
5. ELSO. (2009). Extracorporeal Life Support Organization (ELSO) Patient Specific Supplements to the ELSO General Guidelines. Retrieved March 5, 2019, from http://square.umin.ac.jp/jrcm/pdf/ecmo/ecmotext12.pdf.
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11. Lee, J. J., Han, S. J., Kim, H. S., Hong, K. S., Choi, H. H., Park, K. T., . . . Ha, S. O. (2016). Out-of-hospital cardiac arrest patients treated with cardiopulmonary resuscitation using extracorporeal membrane oxygenation: Focus on survival rate and neurologic outcome. Scandinavian Journal of Trauma, Resuscitation and Emergency Medicine, 24(1). doi:10.1186/s13049-016-0266-8
12. Schober, A., Sterz, F., Herkner, H., Wallmueller, C., Weiser, C., Hubner, P., & Testori, C. (2017). Emergency extracorporeal life support and ongoing resuscitation: A retrospective comparison for refractory out-of-hospital cardiac arrest. Emergency Medicine Journal, 34(5), 277-281. doi:10.1136/emermed-2015-205232
13. Fjølner, J., Greisen, J., Jørgensen, M. R., Terkelsen, C. J., Ilkjaer, L. B., Hansen, T. M., . . . Gjedsted, J. (2016). Extracorporeal cardiopulmonary resuscitation after out-of-hospital cardiac arrest in a Danish health region. Acta Anaesthesiologica Scandinavica, 61(2), 176-185. doi:10.1111/aas.12843
14. Ellouze, O., Vuillet, M., Perrot, J., Grosjean, S., Missaoui, A., Aho, S., . . . Girard, C. (2017). Comparable Outcome of Out-of-Hospital Cardiac Arrest and In-Hospital Cardiac Arrest Treated With Extracorporeal Life Support. Artificial Organs, 42(1), 15-21. doi:10.1111/aor.12992
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17. Yannopoulos, D., Bartos, J. A., Raveendran, G., Conterato, M., Frascone, R. J., Trembley, A., . . . Aufderheide, T. P. (2017). Coronary Artery Disease in Patients With Out-of-Hospital Refractory Ventricular Fibrillation Cardiac Arrest. Journal of the American College of Cardiology, 70(9), 1109-1117. doi:10.1016/j.jacc.2017.06.059
18. Link, M. S., Berkow, L. C., Kudenchuk, P. J., Halperin, H. R., Hess, E. P., Moitra, V. K., . . . Donnino, M. W. (2015). Part 7: Adult Advanced Cardiovascular Life Support. Circulation, 132(18 suppl 2). doi:10.1161/cir.0000000000000261
