Extracorporeal membrane oxygenation
In intensive care medicine, extracorporeal membrane oxygenation (ECMO) is an extracorporeal technique of providing both cardiac and respiratory support oxygen to patients whose heart and lungs are so severely diseased that they can no longer serve their function.
An ECMO machine is similar to a heart-lung machine. To initiate ECMO, cannulae are placed in large blood vessels to provide access to the patient's blood. Anticoagulant drugs (usually heparin) are given to prevent blood clotting. The ECMO machine continuously pumps blood from the patient through a "membrane oxygenator" that imitates the gas exchange process of the lungs, i.e. it removes carbon dioxide and adds oxygen. Oxygenated blood is then returned to the patient.
There are several forms of ECMO, the two most common of which are veno-arterial (VA) and veno-venous (VV). In both modalities, blood drained from the venous system is oxygenated outside of the body. In VA ECMO, this blood is returned to the arterial system and in VV ECMO the blood is returned to the venous system. In VV ECMO, no cardiac support is provided.
VV ECMO can provide sufficient oxygenation for several weeks, allowing diseased lungs to heal while the potential additional injury of aggressive mechanical ventilation is avoided. It may therefore be life-saving for some patients. However, due to the high technical demands, cost, and risk of complications (such as bleeding under anticoagulant medication), ECMO is usually only considered as a last resort therapy.
ECMO is most commonly used in NICUs (Neonatal Intensive Care Units), for newborns in pulmonary distress. It is around 75% effective in saving the newborn's life. Newborns can't be placed on ECMO if they are under 4 and a half pounds, thus ruling out the device for most premature newborns. Newborn infants are occasionally placed on ECMO due to the lack of a fully functioning respiratory system or other birth defect, but the survival rates drop to roughly 33%. The time limit for a newborn is usually around 21 day max. However, Dr. Thomas Krummel, Chairman of General Surgery at Stanford University, has the record for the longest survivor on ECMO at 62 days.
"ECMO can have dangerous side effects. The large catheters inserted in the baby's neck can provide a fertile field for infection, resulting in fatal sepsis." (Excerpted from How Doctors Think by Jerome Groopman, M.D.
In Adults ECMO survival rates are around 60%. In Adult VV ECMO there are reports of patients being supported for over ten weeks. ECMO has yet to have proven survival benefit in adults with ARDS.
Management of the ECMO circuit is done by a team of ECMO specialists that includes ICU physicians, perfusionists, respiratory therapists and registered nurses that have received training in this specialty.
In VA ECMO, patients whose cardiac function doesn't recover sufficiently to be weaned from ECMO may be bridged to a Ventricular assist device (VAD) or Transplant.