ECMO in COVID-19: do not blame the tool
Authors: Alain Vuylsteke
Journal: The Lancet (2021)

Initial reports suggested a high mortality for COVID-19 patients supported with extracorporeal membrane oxygenation (ECMO).1Henry BM Lippi G Poor survival with extracorporeal membrane oxygenation in acute respiratory distress syndrome (ARDS) due to coronavirus disease 2019 (COVID-19): pooled analysis of early reports.J Crit Care. 2020; 58: 27-28Crossref PubMed Scopus (195) Google Scholar However, subsequent cohort studies reported ECMO outcomes did not differ between COVID-19 and other types of acute respiratory distress,2Barbaro RP MacLaren G Boonstra PS et al.Extracorporeal membrane oxygenation support in COVID-19: an international cohort study of the Extracorporeal Life Support Organization registry.Lancet. 2020; 396: 1071-1078Summary Full Text Full Text PDF PubMed Scopus (618) Google Scholar, 3Schmidt M Hajage D Lebreton G et al.Extracorporeal membrane oxygenation for severe acute respiratory distress syndrome associated with COVID-19: a retrospective cohort study.Lancet Respir Med. 2020; 8: 1121-1131Summary Full Text Full Text PDF PubMed Scopus (317) Google Scholar encouraging many to provide ECMO when deemed appropriate, including coordinating its delivery at national level in England.4Jooste R Rowan KM Symes N Vuylsteke A Scaling up a National Extracorporeal Membrane Oxygenation Referral Service for adult patients in acute severe respiratory failure at the time of a pandemic.J Intensive Care Soc. 2021; (https://doi.org/10.1177%2F17511437211022129 published online June 4.)Crossref Scopus (1) Google Scholar In The Lancet, Ryan P Barbaro and colleagues5Barbaro R MacLaren G Boonstra PS et al.Extracorporeal membrane oxygenation for COVID-19: evolving outcomes from the International Extracorporeal Life Support Organization Registry.Lancet. 2021; (published online Sept 29.)https://doi.org/10.1016/S0140-6736(21)01960-7Summary Full Text Full Text PDF PubMed Scopus (226) Google Scholar report an analysis of an international cohort of 4812 patients (aged ≥16 years) with COVID-19 who were supported with ECMO. Patients were divided into three groups based on the time and centre at which ECMO was started. The median age of patients was 49–51 years across the three groups, and 3523 (73%) were male. Data on race were not reported. The primary outcome was in‑hospital mortality, assessed 90 days after ECMO started. The findings suggest that mortality rates for ECMO-supported patients have increased by 15% between an arbitrarily set early and late stage of the pandemic (on or before May 1 vs after May 1, 2020); the mortality rate was 36·9% (95% CI 34·1–39·7) for patients who started ECMO on or before May 1 versus 51·9% (50·0–53·8) for patients who started ECMO after May 1. Mortality was even higher at 58·9% (55·4–62·3) for patients treated at centres that only offered ECMO after May 1. This analysis shows that the majority of patients supported with ECMO will now die. ECMO is a simple concept allowing gas exchange and can be used to support patients with acute lung injury. It is complex in its execution, requiring trained staff and specialist equipment, and has a high burden of complications.6Zangrillo A Landoni G Biondi-Zoccai G et al.Complications-and-mortality-of-extracorporeal-membrane-oxygenation.pdf.Crit Care Resusc. 2015; 3: 172-178Google Scholar ECMO is not a treatment or a therapy, it simply supports patients with failing lungs, providing time for lung recovery or—exceptionally—to be bridged to lung transplantation.7Bharat A Machuca TN Querrey M et al.Early outcomes after lung transplantation for severe COVID-19: a series of the first consecutive cases from four countries.Lancet Respir Med. 2021; 9: 487-497Summary Full Text Full Text PDF PubMed Scopus (163) Google Scholar The premise of ECMO is that it decreases the added physiological insult caused by mechanical ventilation, by permitting clinicians to use a less damaging mode of lung ventilation. This hypothesis is elegant but ECMO has never been proven to be superior to not using ECMO in randomised controlled trials.8Graham PL Moran JL ECMO, ARDS and meta-analyses: Bayes to the rescue?.J Crit Care. 2020; 59: 49-54Crossref PubMed Scopus (2) Google Scholar Providing ECMO is fraught with difficulties and experience brings benefits. Barbaro and colleagues report that centres with more ECMO experience—defined as treating at least nine patients on or before May 1, 2020—have better outcomes (risk-adjusted mortality rate of 0·56 (95% CI 0·43–0·75) relative to centres with less experience).5Barbaro R MacLaren G Boonstra PS et al.Extracorporeal membrane oxygenation for COVID-19: evolving outcomes from the International Extracorporeal Life Support Organization Registry.Lancet. 2021; (published online Sept 29.)https://doi.org/10.1016/S0140-6736(21)01960-7Summary Full Text Full Text PDF PubMed Scopus (226) Google Scholar This phenomenon has been seen in many other clinical scenarios,9Nguyen Y-L Wallace DJ Yordanov Y et al.The volume-outcome relationship in critical care.Chest. 2015; 148: 79-92Summary Full Text Full Text PDF PubMed Scopus (108) Google Scholar and is thought to be a key explanation for the superiority of being allocated to an ECMO centre (but not always receiving ECMO) in the landmark randomised controlled trial that supported using ECMO in adults with severe respiratory failure.10Peek GJ Mugford M Tiruvoipati R et al.Efficacy and economic assessment of conventional ventilatory support versus extracorporeal membrane oxygenation for severe adult respiratory failure (CESAR): a multicentre randomised controlled trial.Lancet. 2009; 374: 1351-1363Summary Full Text Full Text PDF PubMed Scopus (2628) Google Scholar It also explains why countries such as England have chosen to concentrate all ECMO-supported patients in a few centres.11Warren A Chiu Y-D Villar SS et al.Outcomes of the NHS England National Extracorporeal Membrane Oxygenation Service for adults with respiratory failure: a multicentre observational cohort study.Br J Anaesth. 2020; 125: 259-266Summary Full Text Full Text PDF PubMed Scopus (22) Google Scholar The selection of the right patient at the right time is guided by clinical principles and experience, as well as availability, which might perversely delay commencement of ECMO. Clinicians balance carefully and subjectively the risk and benefit of starting ECMO for every patient. The inflexion point at which one is better than the other is unknown, even if criteria are well defined and regularly reviewed.12Camporota L Meadows C Ledot S et al.Consensus on the referral and admission of patients with severe respiratory failure to the NHS ECMO service.Lancet Respir Med. 2021; 9: e16-e17Summary Full Text Full Text PDF PubMed Scopus (27) Google Scholar Clinicians sometimes select patients who have so much lung damage by the time ECMO is started that there is no possible recovery. Barbaro and colleagues show that, later in the pandemic, patients more often had non-invasive ventilation before ECMO and were given steroids or other specific COVID-19 therapies. The latter is probably reflected in the increased burden of co-infections reported in the post-May 1 cohorts.5Barbaro R MacLaren G Boonstra PS et al.Extracorporeal membrane oxygenation for COVID-19: evolving outcomes from the International Extracorporeal Life Support Organization Registry.Lancet. 2021; (published online Sept 29.)https://doi.org/10.1016/S0140-6736(21)01960-7Summary Full Text Full Text PDF PubMed Scopus (226) Google Scholar Clinicians rely on an experience they do not yet have to allocate patients to ECMO and might miss important characteristics. It is not surprising that outcomes are changing as the pandemic is progressing. In the report by Barbaro and colleagues, no-one knows if some patients survived despite ECMO they did not need, or if some died just because of ECMO, or what happened to those who were denied ECMO—this is still the conundrum to clarify before we decide if ECMO is worth using or not. ECMO cannot be blamed for the increased mortality; it is merely a tool and clinicians still need to understand when to use it for the greatest benefit. Barbaro and colleagues should be commended for scratching the surface and reporting honestly and openly. To date, thousands of patients with COVID-19 have been ventilated in intensive care and a proportion had access to ECMO. Collating and analysing their clinical journeys might help to clarify if ECMO is a tool to keep. I declare no competing interests. Extracorporeal membrane oxygenation for COVID-19: evolving outcomes from the international Extracorporeal Life Support Organization RegistryMortality after ECMO for patients with COVID-19 worsened during 2020. These findings inform the role of ECMO in COVID-19 for patients, clinicians, and policy makers. Full-Text PDF