Extracorporeal membrane oxygenation

Extracorporeal membrane oxygenation
Intervention
ICD-9-CM	39.65

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 or damaged that they can no longer serve their function. Initial cannulation of a patient receiving ECMO is performed by a surgeon and maintenance of the patient is the responsibility of the ECMO Specialist and gives 24/7 monitoring care during the duration of the ECMO treatment.

Uses

One of the new uses is in adults and children with the H1N1 flu.It is also used with children who have respiratory syncytial virus infections. ECMO treatment provides oxygenation until their lung function has sufficiently recovered to maintain appropriate O2 saturation. It is often a last resort.

It is around 75% effective in saving the newborn's life. Newborns cannot be placed on ECMO if they are under 4.5 pounds (2.0 kg), because they have extremely small vessels for cannulation, thus hindering adequate flow because of limitations from cannula size and subsequent higher resistance to blood flow (compare with vascular resistance). Therefore, the device cannot be used for most premature newborns.

ECMO has proven to be useful in treating some severe trauma/polytrauma patients.

Acute respiratory failure

With acute respiratory failure use of ECMO has been shown to improve survival rates. Survival rates from 50—70 percent have been reported in observational and uncontrolled clinical trials. The survival rates reported are better than historical survival rates.

Cardiac failure

The use of ECMO for cardiac failure has been less extensively studied than ECMO for severe acute respiratory failure; thus, additional studies are necessary before ECMO becomes routine for cardiac failure.

Other uses

ECMO use on cadavers can increase the viability rate of transplanted organs.

Procedure

ECMO schema

ECMO in H1N1 patient

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.

System management

ECMO is initiated and installed by a surgeon. Maintenance and management of the ECMO circuit is done by a team or individual termed an ECMO Specialist. ECMO specialists are respiratory practitioners, registered nurses, or perfusionists that have been trained in the specialty.

Types

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.

Veno-arterial (VA)

In veno-arterial ECMO — a venous cannula is usually placed in the right common femoral vein for extraction and an arterial cannula is usually placed into the right femoral artery for infusion. The tip of the femoral venous cannula should be maintained near the junction of the inferior vena cava and right atrium, while the tip of the femoral arterial cannula is maintained in the iliac artery. In Adults accessing the femoral artery is preferred because insertion simpler.

Veno-venous (VV)

In Veno-venous ECMO — venous cannulae are usually placed in the right common femoral vein for drainage and right internal jugular vein for infusion.

Duration

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.

The time limit for a newborn on ECMO is usually around 21 days. The record for the longest survivor on ECMO occurred on January 30, 2008, when a patient at NTU hospital, Taiwan survived a drowning accident after 117 days of ECMO application.

Complications

A common consequence in ECMO-treated adults is neurological injury, which may include subarachnoid hemorrhage, ischemic watershed infarctions, hypoxic-ischemic encephalopathy, unexplained coma, and brain death. Fatal sepsis may occur when the large catheters inserted in the neck provide fertile field for infection. Additional risks include bleeding. In adults, ECMO survival rates are around 60%. ECMO has yet to have proven survival benefit in adults with acute respiratory distress syndrome (ARDS). In VA ECMO, patients whose cardiac function does not recover sufficiently to be weaned from ECMO may be bridged to a ventricular assist device (VAD) or transplant.

In infants aged less than 34 weeks of gestation several physiologic systems are not well-developed, specially the cerebral vasculature and germinal matrix, resulting in high sensitivity to slight changes in pH, PaO₂, and intracranial pressure. Preterm infants are at unacceptably high risk for intraventricular hemorrhage (IVH) if administered ECMO at a gestational age less than 32 weeks. Also later, given the risk of IVH, it has become standard practice to ultrasound the brain prior to administering ECMO.

Heparin-induced thrombocytopenia

Heparin-induced thrombocytopenia (HIT) is increasingly common among patients receiving ECMO. When HIT is suspected, the heparin infusion is usually replaced by a non-heparin anticoagulant.

VA specific complications

• Pulmonary hemorrhage
• Pulmonary infarction
• Aortic thrombosis
• Cerebral hypoxia

External links

• Flow Measurement for ECMO Applications
• ECMO Simulation Site

See also

• Extracorporeal therapy
• Mechanical ventilation