This study examines the temporal evolution of in-hospital survival among 594 consecutive COVID-19 patients treated with extracorporeal membrane oxygenation (ECMO) at 49 hospitals across 21 states in the United States, using data from a prospective database extracted from the Specialty Care Operative Procedural rEgistry (SCOPE). Patients were divided into four groups according to the treatment period: Group A, March to June 2020; Group B, July to December 2020; Group C, January to June 2021; and Group D, July to December 2021.
The average number of cases per hospital was 12.1 (median 6 cases, range 1-73 cases, interquartile range 2-11 cases). ECMO indications and periprocedural management were determined by each center’s protocols and treatment guidelines. No ECMO implant was performed during cardiopulmonary arrest/cardiopulmonary resuscitation.
The overall in-hospital survival was 37.2% (n = 221), 38.6% for VV-ECMO patients and 21.3% for VA-ECMO. Survivors were younger (43 vs. 49 years, p < 0.001), more frequently female, and had fewer days between diagnosis and orotracheal intubation (OTI; 7 vs. 10 days, p < 0.001). Mean age significantly decreased over time, whereas the time elapsed between COVID-19 diagnosis and intubation increased. All adjunct treatments (steroids, convalescent plasma, antivirals, anti-IL6, prostaglandins, and hydroxychloroquine) exhibited significant temporal variations across study periods.
Survival decreased between April and November 2020, improved from November 2020 to May 2021, and declined again between May and December 2021. Treatment timing throughout the pandemic contributed 18.4% to survival variability, with other significant factors contributing over 2%, including age (58.5%), days elapsed from diagnosis to OTI (8.1%), and circuit changes (5.5%). The center’s influence accounted for only 2.7%.
The authors conclude that ECMO is a reasonable strategy for critically ill patients and that minimizing variability in indications and management could maximize survival.
COMMENTARY:
As observed in other series, patients included during the second COVID-19 wave had higher mortality than those in the first. In this and other studies, the most commonly cited reasons include the broadening of indications and an increase in implementing centers, leading to ECMO implantation in higher-risk patients in poorer condition and at centers with less experience. Notably, the influence of the treating center on mortality variation was only 2.7%, despite intense heterogeneity in experience among the participating centers (median 6 cases, range 1-73 cases, interquartile range 2-11 cases). This lack of influence from the center’s experience has been observed in other registries, including one conducted by our Society.
Age is a decisive survival factor (58.5% contribution) as in all prior series. Mean ages and survival cutoff points hover around 40-45 years in the series that have analyzed this, underscoring the need for candidate selection regarding this parameter. Indeed, this series shows that, in the second period, the mean age of treated patients increased, subsequently decreasing as patient selection improved. However, other morbidity markers (diabetes mellitus, renal failure, hypertension, presence of multiple comorbidities) did not worsen in the second period relative to the first.
The observed curves for concomitant therapy management reveal that corticosteroid use, a drug that has significantly contributed to survival in patients with severe COVID-19, was considerably lower in the early study periods than later, which does not explain the lower mortality in the initial phase except through the initial stringent patient selection.
The influence of days between diagnosis and ECMO initiation, especially from diagnosis to OTI, is also a consistent factor across series, potentially carrying critical importance, similar to age. Lung damage from the disease itself worsens with non-protective high-pressure mechanical ventilation (ventilator-induced lung injury) and “self-inflicted” lung injury in spontaneously breathing patients requiring high oxygen, with substantial respiratory effort and consequent significant airway pressure variations.
REFERENCE:
Jacobs JP, Stammers AH, St Louis JD, Tesdahl EA, Hayanga JWA, Morris RJ, et al. Variation in survival in patients with Coronavirus Disease 2019 supported with extracorporeal membrane oxygenation: A multi-institutional analysis of 594 consecutive patients with Coronavirus Disease 2019 supported with extracorporeal membrane oxygenation J Thorac Cardiovasc Surg. 2023 May;165(5):1837-1848. doi: 10.1016/j.jtcvs.2022.05.002.
