The role of extracorporeal membrane oxygénation in COVID-19

The novel coronavirus SARS-C0V-2 (COVID-19) was declared a pandemic in the first quarter of 2020. As its incidence and death toll soared, health organizations raced to develop guidelines outlining effective management strategies to reduce morbidity and mortality. It was estimated that up to 42% of patients would develop COVID-19-associated acute respiratory distress syndrome (CARDS). Current pharmaceutical interventions like dexamethasone and remdesivir have played a significant role in alleviating or reducing the progression of CARDS. CARDS refractory to conventional therapies can develop in up to 33% of patients admitted to the intensive care unit (ICU) with patients requiring either mechanical ventilation or subsequent extracorporeal membrane oxygenation (ECMO). The most common causes of death have also been identified as respiratory failure followed by cardiac failure, the two main indications of ECMO. ECMO has already proven to be an effective method of salvage therapy in non- COVID-19 associated acute respiratory distress syndrome (ARDS) in the previous H1N1 influenza pandemic. Recent studies have also shown the success of ECMO in CARDS, however, there is significant variance in mortality rates across regions due to differences in virulence of COVID-19 subtypes and experience of ECMO centers. Veno-venous ECMO has been the mainstay of treatment in the vast majority of patients suffering from respiratory failure, with veno-arterial ECMO being utilized in an extreme minority of cases of concurrent cardiac failure with great differences in outcomes. This final stage of therapy relies on the simple fact that extravascular oxygenation through a machine can give the damaged lungs and heart time to recover, after which patients can be weaned off slowly. The two most essential factors improving mortality in patients undergoing ECMO seem to be careful patient selection according to extracorporeal life support organization (ELSO) guidelines and optimization of lung protective care, including prone positioning and regulation of driving pressures. Additionally, the role of outcome predicting scores also seems to be of negligible value when ECMO for COVID-19 is considered, with most scoring systems not being able to predict mortality reliably. Finally, while most studies evaluating ECMO in COVID-19 have been observational in nature, there is a distinct lack of large-scale randomized controlled trials explicitly evaluating ECMO and its parameters and the impact these could potentially have on COVID-19 mortality. Therefore, in this chapter, we review the exact role ECMO has played in clinical outcome of CARDS.