Concerns About the Timing and Settings of Initiating Extracorporeal Membrane Oxygenation in Patients With Severe Coronavirus Disease 2019 Pneumonia.

To the Editor:

We read with great interest the clinical investigation reported by Yang et al (1) published in a recent issue of Critical Care Medicine. The authors describe the characteristics of patients with acute respiratory distress syndrome (ARDS) induced by the novel coronavirus disease 2019 (COVID-19) requiring extracorporeal membrane oxygenation (ECMO). They reported the mortality rate of COVID-19-induced ARDS requiring ECMO as 57.1%, which is similar to the 58.3% reported for outcomes (death or coma) in another case series (2). They also described the timing of initiation and the initial settings of ECMO in patients with severe ARDS induced by COVID-19. We would like to discuss whether the strategy they reported can be considered as standard for ECMO treatment for severe COVID-19 pneumonia.

First, regarding the timing of initiating ECMO, the authors state that earlier initiation after mechanical ventilation may be associated with improved outcomes. Although early initiation is reported to be associated with good prognosis in adult ARDS patients (3), COVID-19 pneumonia is reported to present with features different from typical ARDS (4). Would different phenotypes of respiratory failure require different ECMO treatment strategies? We are still doubtful whether early initiation of ECMO can be considered similarly for typical ARDS and COVID-19 pneumonia. Addressing this will require comparisons between early initiation and late initiation groups.

Second, the initial setting of ECMO in the study by Yang et al (1) seems to be unique. The authors report that many patients developed bradycardia while the centrifugal pump was on. This raises the question of whether this phenomenon is unique to COVID-19 pneumonia. Looking at the many COVID-19 case series reported to date, we find no descriptions of bradycardia elsewhere. To avoid bradycardia, the authors suggest increasing ECMO pump rotation slowly from 1,500 revolutions per minute (rpm) to the target rotation at increments of 500 rpm every 10 minutes. We speculate venovenous ECMO does not, in fact, have a significant effect on hemodynamics when initiating ECMO as long as a sufficient intravascular volume is maintained. Another report of patients with COVID-19 pneumonia requiring ECMO also described gradually increasing the rotation speed of the centrifugal pump when starting ECMO (5), but at a seemingly faster rate than Yang et al (1) reported. We question then whether it is actually possible to prevent bradycardia using the authors’ method.

Finally, have the laboratory test values presented for survivors and nonsurvivors in Table 2 in (1) mistakenly been switched, given that the authors state that “survivors had a significant lower creatinine than nonsurvivors prior to ECMO”; the numbers in Table 2 in (1) are reversed.

We are still in the pandemic phase of COVID-19, and thus, appropriate indications and methods for initiating ECMO support in critically ill patients with COVID-19 pneumonia are important to establish.