The Role of VV-ECMO in Severe COVID-19 ARDS

*Cathal MacDonncha, Rachel Jooste, John Laffey and Ciara Hanley*

## **Abstract**

Although an established practice in potentially reversible severe respiratory failure, extracorporeal membrane oxygenation (ECMO) support remains controversial. Over the last 50 years, only 4 large scale randomised controlled trials relating to ECMO have been conducted in patients with ARDS. A meta-analysis of only 2 studies has demonstrated survival benefit in those supported with ECMO compared to optimal conventional therapy. With the advent of the COVID pandemic, ECMO utilisation increased, the guidelines evolved, and an unprecedented number of patients were referred for and managed with ECMO support. Approximately 15,000 patients have been supported to date, predominantly using veno-venous ECMO, with an overall in-hospital 90-day mortality of 47%. Although published data reported an increase in ECMO mortality to nearly 60% as the pandemic progressed, this was likely multifactorial, as subsequent data has demonstrated more promising mortality results. This highlights the unique challenges pertaining to patient selection and implementation of this finite support amid an evolving pandemic with many unknowns. Judicious and ethical patient selection is essential to ensure use for the greatest benefit. In this chapter we will outline the unique pathophysiology and clinical features of COVID-ARDS, indications for ECMO referral and patient selection, and implementation during the COVID-19 pandemic.

**Keywords:** COVID-19, ARDS, VV ECMO, COVID-19 pathophysiology, hypoxaemia

## **1. Introduction**

With the outbreak of COVID, extracorporeal membrane oxygen support (ECMO) utilisation exponentially increased, and the guidelines on ECMO referral, selection, and patient management rapidly evolved to cope with the unprecedented scale of the pandemic [1]. To date, an unparalleled number of patients have been referred for and managed with ECMO. According to the Extracorporeal Life Support Organisation (ELSO) COVID-19 ECMO registry, approximately 15,000 patients have been supported so far, predominantly using veno-venous ECMO (VV ECMO), with an overall in-hospital 90-day mortality of 47% [2]. Although the pandemic led to an upscale in ECMO use, ECMO mortality actually increased to nearly 60% as the pandemic progressed over 2020 [3]. However, this increase is likely a function of multiple

interconnected factors as more recent mortality data has been more optimistic with an estimated survival probability of 87% on Day 7 ECMO and 78% at 90-days, compared with 83% and 64% respectively in the conventional management group [4]. The type of variant, patient demographic and comorbidity, a more severe COVID-ARDS phenotype and lack of reversibility, increased and/ or more resistant co-infections (some of which are possibly associated with steroids and novel COVID-19 therapies), and treatment in a low vs. high volume ECMO centre may have contributed to this mortality variance. The inconsistency in patient outcomes highlights the unique challenges pertaining to judicious and ethical patient selection, and appropriate application of this expensive and finite mode of support amid an evolving pandemic with many unknowns in order to ensure its use for the greatest benefit.
