Extracorporeal Strategies in Acute Respiratory Distress Syndrome

Abstract

Despite the breadth of life-sustaining interventions available, mortality in patients with acute respiratory distress syndrome (ARDS) remains high. A greater appreciation of the potential iatrogenic injury associated with the use of mechanical ventilation has led clinicians and researchers to seek alternatives. Extracorporeal life support (ECLS) may be used to rescue patients with severely impaired gas exchange and provide time for injured lungs to recover while treating the underlying disease. In patients with ARDS, venovenous (VV) ECLS is commonly used, where venous blood is drained into a circuit that passes through a membrane lung, which provides gas exchange, and then returned to the venous system. VV-ECLS can be configured as a system that uses higher blood flows with extracorporeal membrane oxygenation (VV-ECMO) or as one that uses lower blood flows for extracorporeal carbon dioxide removal (VV-ECCO2R). Recent studies support the use of VV-ECMO in patients with severe ARDS who present with refractory gas exchange despite the use of lung-protective mechanical ventilation, positive end-expiratory pressure optimization, neuromuscular blockade, and prone positioning. The optimal management of patients during ECLS (i.e., anticoagulation, transfusions, mechanical ventilation) and the role of ECCO2R in the management of ARDS remain to be determined.

How I Select Which Patients With ARDS Should Be Treated With Venovenous Extracorporeal Membrane Oxygenation

“…3 The development of scoring systems and mortality prediction for patients receiving VV-ECMO has been difficult because of changes in ECMO technology over time, the relatively small and highly specific study populations, and large patient heterogeneity. Therefore, VV-ECMO has often been used for rescue, 5,18 when perhaps we should be using it early when high-risk features are present, 7,15,20 and the timely correction of both life-threatening gas exchange and hemodynamics (eg, right ventricular failure) may halt the progression of organ failure. These decisions are often made on a case by case basis, but usually take into account the underlying pathophysiology (and therefore reversibility) of the lung injury, 5,18,21 any preexisting comorbidities and their physiological reserve, 22 risk vs benefit of implementing ECMO, and absence of significant contraindications.…”

“…It is usually based on the presence of specific clinical factors that indicate the patient has passed the point of recovery based on their hemodynamics, mechanical ventilation profile, or perceived physiological reserve. 5,15,18,22 In this tenor, it might be helpful to take into consideration clinical scenarios where ECMO is unlikely to be successful, such as in patients with ARDS and refractory septic shock with normal (or hyperdynamic) biventricular function. 52 In patients with severe vasodilatory shock that is unresponsive to multiple vasopressors, VV-ECMO will be ineffective in providing enough flow through the oxygenator to reverse the hypoxemia.…”

“…2,14 Because of the potential devastating complications, the impact on long-term functional outcomes, and the costs and strain on the health-care system related to ECMO deployment, appropriate patient selection is the key to its success. 15,16 Taken together, it makes drawing the line of when ECMO should or should not be offered far from straightforward.…”

Extracorporeal Membrane Oxygenation for Severe Respiratory Failure During Respiratory Epidemics and Pandemics: A Narrative Review

“…For example, the use of biocompatible circuits and hollow-fibre oxygenators have contributed to a reduced need for anticoagulation. 7 This is demonstrated by the recent EOLIA trial, where severe bleeding complications were rare, with a 2% incidence of haemorrhagic stroke in the ECMO group, compared to 4% in the non-ECMO group. 14 Finally, national and institutional protocols must be provided to guide physician decisions regarding resource-allocation and patient selection for ECMO for critically ill patients with COVID-19, ideally by considering multiple ethical principles in conjunction with the use of prediction scoring systems and expert clinical judgement.…”

“…For clinical aspects that we did not include, we refer readers to other excellent review articles on the use of ECMO in the ICU. 6,7 For the purpose of this narrative review, we searched MEDLINE, EMBASE and Google Scholar using the following MESH terms and keywords: ECMO, epidemics, pandemics, SARS, H1N1pdm09, MERS-CoV and COVID-19. Additionally, we examined the references of articles found and included those that we considered appropriate for this focused narrative review.…”