Extracorporeal membrane oxygenation (ECMO) provides a potential rescue therapy for critically ill COVID-19 patients. ECMO therapy comprises of a machine that oxygenates a patient’s blood outside the body. Tubing connects blood flow to an artificial lung; this lung adds oxygen to and extracts carbon dioxide from the blood. The machine warms the blood to body temperature and pumps it back into the patient’s body.1
Two types of extracorporeal membrane oxygenation exist: venovenous (VV) and venoarterial (VA). In VV ECMO, the machine removes blood from the venous system, passes it through the oxygenator, and returns the blood to the lungs.2 VV ECMO only provides pulmonary support. VA ECMO, however, provides both pulmonary and hemodynamic support.3 In VA ECMO, the machine removes blood from the venous system and returns it to the arterial system.
Past precedent suggests that ECMO therapy may prove beneficial for COVID-19 patients who suffer acute respiratory distress syndrome (ARDS). Previously, numerous studies concluded that ECMO therapy appeared to lower mortality in influenza A (H1N1)-related ARDS patients compared to those who did not receive ECMO therapy.4–8 Likewise, a retrospective study recommended ECMO as a rescue therapy for Middle East respiratory syndrome (MERS) patients with refractory respiratory failure.9 However, medicine has little experience that can directly inform the administration of ECMO therapy to critically ill COVID-19 patients.10
Only a few studies report ECMO therapy for COVID-19-related ARDS patients.11–17 These studies show an approximate mortality of 82.3% for the adult patients who receive ECMO therapy.18 Yang et al.,14 for example, reported that five of six patients on ECMO died; the sixth patient remained on ECMO at the study’s conclusion. Furthermore, Zhang et al.17 observed 10 patients on ECMO: the hospital discharged two patients, three died, and five remained on ECMO when the study concluded.
Recommendations suggest that physicians consider ECMO only when conventional management fails.19 Generally, protocol classifies patients who, despite optimal care, experience high mortality risk and a PaO2/FiO2 ratio below 100 as potential ECMO candidates.20 Specifically, ECMO candidates present as adult and pediatric patients with ARDS-related refractory hypoxemia in whom lung-protective ventilation fails.21 Protocol, however, strongly emphasizes the maximization of conventional ARDS therapies prior to ECMO consideration.22 These therapies include prone positioning, neuromuscular blockade, positive end-expiratory pressure (PEEP), inhaled pulmonary vasodilators, and recruitment maneuvers.22,23
References
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4. The Australia and New Zealand Extracorporeal Membrane Oxygenation (ANZ & ECMO) Influenza Investigators. Extracorporeal Membrane Oxygenation for 2009 Influenza A(H1N1) Acute Respiratory Distress Syndrome. JAMA 302, 1888–1895 (2009).
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19. Alhazzani, W. et al. Surviving Sepsis Campaign: guidelines on the management of critically ill adults with Coronavirus Disease 2019 (COVID-19). Intensive Care Med. 46, 854–887 (2020).
20. Bartlett, R. H. et al. Initial ELSO Guidance Document: ECMO for COVID-19 Patients with Severe Cardiopulmonary Failure. Asaio J. 66, 472–474 (2020).
21. World Health Organization. Clinical management of severe acute respiratory infection (SARI) when COVID-19 disease is suspected. Interim guidance. 19 http://www.pimr.pl/index.php/issues/2020-vol-16-no-1/clinical-management-of-severe-acute-respiratory-infection-sari-when-covid-19-disease-is-suspected-interim-guidance?aid=1463 (2020).
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27. Ramanathan, K. et al. Planning and provision of ECMO services for severe ARDS during the COVID-19 pandemic and other outbreaks of emerging infectious diseases. Lancet Respir. Med. 8, 518–526 (2020).