Extracorporeal membrane oxygenation
Extracorporeal membrane oxygenation (ECMO), is a form of extracorporeal life support, providing prolonged cardiac and respiratory support to persons whose heart and lungs are unable to provide an adequate amount of oxygen, gas exchange or blood supply (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.
Most contraindications are relative, balancing the risks of the procedure versus the potential benefits. The relative contraindications are:
Side effects and complications[edit]
Neurologic[edit]
A common consequence in ECMO-treated adults is neurological injury, which may include intracerebral hemorrhage, subarachnoid hemorrhage, ischemic infarctions in susceptible areas of the brain, hypoxic-ischemic encephalopathy, unexplained coma, and brain death.[21] Bleeding occurs in 30 to 40% of those receiving ECMO and can be life-threatening. It is due to both the necessary continuous heparin infusion and platelet dysfunction. Meticulous surgical technique, maintaining platelet counts greater than 100,000/mm3, and maintaining the target activated clotting time reduce the likelihood of bleeding.
Blood[edit]
Heparin-induced thrombocytopenia (HIT) is increasingly common among people receiving ECMO. When HIT is suspected, the heparin infusion is usually replaced by a non-heparin anticoagulant.[22]
There is retrograde blood flow in the descending aorta whenever the femoral artery and vein are used for VA (Veno-Arterial) ECMO. Stasis of the blood can occur if left ventricular output is not maintained, which may result in thrombosis.
Bridge-to-assist device[edit]
In VA ECMO, those whose cardiac function does not recover sufficiently to be weaned from ECMO may be bridged to a ventricular assist device (VAD) or transplant. A variety of complications can occur during cannulation, including vessel perforation with bleeding, arterial dissection, distal ischemia, and incorrect location.
Children[edit]
Preterm infants, having inefficiency of the heart and lungs, are at unacceptably high risk for intraventricular hemorrhage (IVH) if ECMO is performed at a gestational age less than 32 weeks.[23]
Infections[edit]
The prevalence of hospital-acquired infections during ECMO is 10-12% (higher compared to other critically ill patients). Coagulase-negative staphylococci, Candida spp., Enterobacteriaceae and Pseudomonas aeruginosa are the most frequently involved pathogens. ECMO patients display a high incidence of ventilator-associated pneumonia (24.4 cases/1000 ECMO days), with a major role played by Enterobacteriaceae. The infectious risk was shown to increase along the duration of the ECMO run, which is the most important risk factor for the development of infections. Other ECMO-specific factors predisposing to infections include the severity of illness in ECMO patients, the high risk of bacterial translocation from the gut and ECMO-related impairment of the immune system. Another important issue is the microbial colonisation of catheters, ECMO cannulae and the oxygenator.[24]
History[edit]
ECMO was developed in the 1950s by John Gibbon, and then by C. Walton Lillehei. The first use for neonates was in 1965.[36][37]
Banning Gray Lary[38] first demonstrated that intravenous oxygen could maintain life. His results were published in Surgical Forum in November 1951.[39] Lary commented on his initial work in a 2007 presentation wherein he writes, "Our research began by assembling an apparatus that, for the first time, kept animals alive while breathing pure nitrogen. This was accomplished with very small bubbles of oxygen injected into the blood stream. These bubbles were made by adding a 'wetting agent' to oxygen being forced through a porcelain filter into the venous blood stream. Shortly after its initial presentation to the American College of Surgeons, this apparatus was reviewed by Walton Lillehei who with DeWall made the first practical heart[–]lung machine that employed a bubble oxygenator. With variations such machines were used for the next twenty years."
Research[edit]
Randomized controlled trials (RCTs)[edit]
Four randomized controlled trials (RCTs) have been conducted to evaluate the effectiveness of ECMO in respiratory failure patients. Early trials conducted by Zapol et al.[60] and Morris et al.[61] were plagued by technical challenges related to the ECMO technology available in the 1970s and 1990s. The CESAR[62] and EOLIA[63] trials utilized modern ECMO systems and are considered the central ECMO RCTs.