Extracorporeal membrane oxygenation (ECMO), also known as extracorporeal life support (ECLS), is an extracorporeal technique of providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequate amount of gas exchange or perfusion to sustain life. The technology for ECMO is largely derived from cardiopulmonary bypass, which provides shorter-term support with arrested native circulation. The device used is a membrane oxygenator, also known as an artificial lung.
ECMO works by temporarily drawing blood from the body to allow artificial oxygenation of the red blood cells and removal of carbon dioxide. Generally, it is used either post-cardiopulmonary bypass or in late-stage treatment of a person with profound heart and/or lung failure, although it is now seeing use as a treatment for cardiac arrest in certain centers, allowing treatment of the underlying cause of arrest while circulation and oxygenation are supported. ECMO is also used to support patients with the acute viral pneumonia associated with COVID-19 in cases where artificial ventilation alone is not sufficient to sustain blood oxygenation levels.
Medical uses
Guidelines that describe the indications and practice of ECMO are published by the Extracorporeal Life Support Organization (ELSO). Criteria for the initiation of ECMO vary by institution, but generally include acute severe cardiac or pulmonary failure that is potentially reversible and unresponsive to conventional management. Examples of clinical situations that may prompt the initiation of ECMO include the following:
Hypoxemic respiratory failure with a ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2) of <100 mmHg despite optimization of the ventilator settings, including the fraction of inspired oxygen (FiO2), positive end-expiratory pressure (PEEP), and inspiratory to expiratory (I:E) ratio Hypercapnic respiratory failure with an arterial pH <7.20 Refractory cardiogenic shock Cardiac arrest Failure to wean from cardiopulmonary bypass after cardiac surgery As a bridge to either heart transplantation or placement of a ventricular assist device As a bridge to lung transplantation Septic shock is a more controversial but increasingly studied use of ECMO Hypothermia, with a core temperature between 28 and 24 °C and cardiac instability, or with a core temperature below 24 °C.
In those with cardiac arrest or cardiogenic shock, it appears to improve survival and good outcomes.
Use in COVID-19 patients
Beginning in early February 2020, doctors in China have increasingly been using ECMO as an adjunct support for patients presenting with acute viral pneumonia associated with SARS-CoV-2 infection (COVID-19) when, with ventilation alone, the blood oxygenation levels still remain too low to sustain the patient. The initial reports indicate that it is assisting in restoring patients' blood oxygen saturation and reducing fatalities among the approximately 3% of severe cases where it has been utilized. For critically ill patients, the mortality rate reduces from around 59–71% with conventional therapy to approximately 46% with extracorporeal membrane oxygenation. A March 2021 Los Angeles Times cover story illustrated the efficacy of ECMO in an extremely challenging COVID patient. In February 2021, three pregnant Israeli women who had "very serious" cases of COVID-19 were given ECMO treatment and it seemed this treatment option would continue.
Outcomes
Early studies had shown survival benefit with use of ECMO for people in acute respiratory failure especially in the setting of acute respiratory distress syndrome. A registry maintained by ELSO of nearly 51,000 people that have received ECMO has reported outcomes with 75% survival for neonatal respiratory failure, 56% survival for pediatric respiratory failure, and 55% survival for adult respiratory failure. Other observational and uncontrolled clinical trials have reported survival rates from 50 to 70%. These reported survival rates are better than historical survival rates. Even though ECMO is used for a range of conditions with varying mortality rates, early detection is key to prevent the progression of deterioration and increase survival outcomes.
In the United Kingdom, veno-venous ECMO deployment is concentrated in designated ECMO centers to potentially improve care and promote better outcomes.