Extra-Corporeal Membrane Oxygenation (ECMO)

Extra-Corporeal Membrane Oxygenation (ECMO), also known as extracorporeal life support (ECLS), is a temporary life support technique to keep patients alive when their heart and/or lungs stop functioning. It can be used to provide cardiac and respiratory support for up to a few weeks, during which the patient recovers. 

If recovery does not occur, the patient can receive a longer-term mechanical assist device or undergo heart transplantation. Patients on ECMO support are given an anticoagulant, to prevent blood clotting in the external system.

Treatment Risks

ECMO treatment is a high-risk procedure with significant complications including bleeding, stroke, sepsis and limb ischemia, and should only be used when all other conventional treatments have failed. These conventional treatments include mechanical ventilation (breathing machine), inotropes (medications that help with heart's contractions), intra-aortic balloon pump (a device that helps the heart pump more blood). In this group of critically ill patients, ECMO can save approximately 60% with respiratory failure, 40% with cardiogenic shock, and 30% with cardiac arrest.

The use of ECMO is generally contraindicated or not advisable if patient is/has:

Nonetheless, decisions on ECMO initiation are made based on the risks and benefits it could bring to the individual case. When a patient is identified to be requiring ECMO, the referring physician will discuss with the ECMO centre on the treatment plan.

ECMO uses a modified ‘heart-lung machine’ that is routinely used for open-heart surgery. It involves the use of a centrifugal pump (artificial heart), which takes over the work of the heart and an oxygenator (artificial lung), which takes over the work of the lungs. 

A large bore cannula is placed in a large vein to draw venous blood out into the ECMO circuit. This venous blood is oxygenated and decarboxylated by the oxygenator in the circuit. The treated blood is warmed up using a heat-exchanger in the circuit and pumped back into the patient using the centrifugal pump.

There are two types of ECMO – Venoarterial (VA) ECMO, which provides the heart and lung support, and venovenous (VV) ECMO, which provides only lung support.

 

(above) Venoarterial (VA) ECMO (left) provides both respiratory and hemodynamic support, with the ECMO circuit connected in parallel to the heart and lungs, while venovenous (VV) ECMO (right) provides only lung support and the circuit is connected in series to the heart and lungs.

VA ECMO supports the function of the patient's heart and lungs by diverting most of a person's blood to the ECMO circuit without the blood flowing through the patient's heart and lungs. VA ECMO draws out blood from a large vein and into the ECMO circuit. The venous blood in the ECMO circuit is oxygenated and returned into a large artery, allowing oxygen-rich blood to circulate through the body. In adults, VA ECMO is commonly used in conditions causing cardiac arrest and cardiogenic shock such as heart attack, myocarditis, cardiomyopathy, pulmonary embolism and primary graft failure after heart transplant. It is also used in conditions like poisoning, endocrine emergencies, sepsis, trauma, and organ donation. Most commonly, patients are on VA ECMO for five to 10 days.

VV ECMO supports the function of patient’s lungs only, hence a persons’ heart must still function well to meet the body's needs. It draws most of the patient’s venous blood out of a large vein and into the ECMO circuit. The venous blood in the ECMO circuit is oxygenated and returned to the right atrium and the patient's own heart pumps the blood throughout the body. It is therefore important that the patient’s heart is strong enough to pump the oxygenated blood in the right atrium, through the non-functioning lungs to the rest of the body. In adults, common indications for VV ECMO is lung failure due to pneumonia and adult respiratory distress syndrome. Most commonly, patients are on VV ECMO for 10 to 14 days.

NHCS has been performing ECMO since 2001 and is the largest ECMO centre in Singapore, performing about 75 procedures per year. NHCS has a mobile unit that can be activated to initiate ECMO at peripheral hospitals and bring the patient back to NHCS for care management.