Extra-Corporeal Membrane Oxygenation (ECMO)

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.

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.

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 to body temperature 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.

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.