extracorporeal membrane oxygenation

Extracorporeal Membrane Oxygenation 

Definition

Extracorporeal membrane oxygenation (ECMO) is a special procedure that uses an artificial heart-lung machine to take over the work of the lungs (and sometimes also the heart). ECMO is used most often in newborns and young children, but it also can be used as a last resort for adults whose heart or lungs are failing.

Purpose

In newborns, ECMO is used to support or replace an infant's undeveloped or failing lungs by providing oxygen and removing carbon dioxide waste products so the lungs can rest. Infants who need ECMO may include those with:

• meconium aspiration syndrome, (breathing in of a newborn's first stool by a fetus or newborn, which can block air passages and interfere with lung expansion)
• persistent pulmonary hypertension, (a disorder in which the blood pressure in the arteries supplying the lungs is abnormally high)
• respiratory distress syndrome (a lung disorder usually of premature infants that causes increasing difficulty in breathing, leading to a life-threatening deficiency of oxygen in the blood)
• congenital diaphragmatic hernia, (the profusion of part of the stomach through an opening in the diaphragm)
• pneumonia
• blood poisoning

ECMO is also used to support a child or adult patient's damaged, infected, or failing lungs for a few hours to allow treatment or healing. It is effective for those patients with severe, but reversible, heart or lung problems who haven't responded to treatment with a ventilator, drugs, or extra oxygen. Adults and children who need ECMO usually have one of these problems:

• heart failure
• pneumonia
• respiratory failure caused by trauma or severe infection

The ECMO procedure can help a patient's lungs and heart rest and recover, but it will not cure the underlying disease. Any patient who requires ECMO is seriously ill and will likely die without the treatment. Because there is some risk involved, this method is used only when other means of support have failed.

Precautions

Typically, ECMO patients have daily chest x rays and blood work, and constant vital sign monitoring. They are usually placed on a special rotating bed that is designed to decrease pressure on the skin and help move secretions from the lungs.

After the patient is stable on ECMO, the breathing machine settings will be lowered to "rest" settings, which allows the lungs to rest without the risk of too much oxygen or pressure from the ventilator.

Description

There are two types of ECMO: Venoarterial (V-A) ECMO supports the heart and lungs, and is used for patients with blood pressure or heart functioning problems in addition to respiratory problems. Venovenous (V-V) ECMO supports the lungs only.

V-A ECMO requires the insertion of two tubes, one in the jugular and one in the carotid artery. In the V-V ECMO procedure, the surgeon places a plastic tube into the jugular vein through a small incision in the neck.

Once in place, the tubes are connected to the ECMO circuit, and then the machine is turned on. The patient's blood flows out through the tube and may look very dark because it contains very little oxygen. A pump pushes the blood through an artificial membrane lung, where oxygen is added and carbon dioxide is removed. The size of the artificial lung depends on the size of the patient; sometimes adults need two lungs. The blood is then warmed and returned to the patient. A steady amount of blood (called the flow rate) is pushed through the ECMO machine every minute. As the patient improves, the flow rate is lowered.

Many patients require heavy sedation while they are on ECMO to lessen the amount of oxygen needed by the muscles.

As the patient improves, the amount of ECMO support will be decreased gradually, until the machine is turned off for a brief trial period. If the patient does well without ECMO, the treatment is stopped.

Typically, newborns remain on ECMO for three to seven days, although some babies need more time (especially if they have a diaphragmatic hernia). Once the baby is off ECMO, he or she will still need a ventilator (breathing machine) for a few days or weeks. Adults may remain on ECMO for days to weeks, depending on the condition of the patient, but treatment may be continued for a longer time depending on the type of heart or lung disease, the amount of damage to the lungs before ECMO was begun, and the presence of any other illnesses or health problems.

Preparation

Before ECMO is begun, the patient receives medication to ease pain and restrict movement.

Aftercare

Because infants on ECMO may have been struggling with low oxygen levels before treatment, they may be at higher risk for developmental problems. They will need to be monitored as they grow.

Risks

Bleeding is the biggest risk for ECMO patients, since blood thinners are given to guard against blood clots. Bleeding can occur anywhere in the body, but is most serious when it occurs in the brain. This is why doctors periodically perform ultrasound brain scans of anyone on ECMO. Stroke, which may be caused by bleeding or blood clots in the brain, has occurred in some patients undergoing ECMO.

If bleeding becomes a problem, the patient may require frequent blood transfusions or operations to control the bleeding. If the bleeding can't be stopped, ECMO will be withdrawn.

Other risks include infection or vocal cord injury. Some patients develop severe blood infections that cause irreversible damage to vital organs.

There is a small chance that some part of the complex equipment may fail, which could introduce air into the system or affect the patient's blood levels, causing damage or death of vital organs (including the brain). For this reason, the ECMO circuit is constantly monitored by a trained technologist.

Normal results

Lungs and/or heart return to healthy functioning.

Abnormal results

Lungs and/or heart do not improve while on ECMO.

Resources

Organizations

American Society of Extra-Corporeal Technology. 11480 Sunset Hills Rd., Ste. 210E, Reston, VA 20190. (703) 435-8556. http://www.amsect.org.

ECMO Moms and Dads. PO Box 53848, Lubbock, TX 79543. (806) 794-0259.

Extracorporeal Life Support Organization. 1327 Jones Dr., Ste. 101, Ann Arbor, MI 48105. (734) 998-6600. http://www.elso.med.umich.edu.

Key terms

Carotid artery — Two main arteries (passageway carrying blood from the heart to other parts of the body) that carry blood to the brain.

Congenital diaphragmatic hernia — The profusion of part of the stomach through an opening in the diaphragm.

Meconium aspiration syndrome — Breathing in of meconium (a newborn's first stool) by a fetus or newborn, which can block air passages and interfere with lung expansion.

Membrane oxygenator — The artificial lung that adds oxygen and removes carbon dioxide.

Pulmonary hypertension — A disorder in which the blood pressure in the arteries supplying the lungs is abnormally high.

Respiratory distress syndrome — A lung disorder usually of premature infants that causes increasing difficulty in breathing, leading to a life-threatening deficiency of oxygen in the blood.

Venoarterial (V-A) bypass — The type of ECMO that provides both heart and lung support, using two tubes (one in the jugular vein and one in the carotid artery).

Venovenous (V-V) bypass — The type of ECMO that provides lung support only, using a tube inserted into the jugular vein.

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oxygenation /ox·y·gen·a·tion/ (ok″sĭ-jĕ-na´shun)

1. the act or process of adding oxygen.

2. the result of having oxygen added.

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extracorporeal membrane oxygenation  (ECMO) a technique for providing respiratory support for newborns, in which the blood is circulated through an artificial lung consisting of two compartments separated by a gas-permeable membrane, with the blood on one side and the ventilating gas on the other.

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oxygenation [ok″sĭ-jĕ-na´shun]

saturation with oxygen.

extracorporeal membrane oxygenation (ECMO) a technique of providing respiratory support; the blood is circulated through an artificial lung consisting of two compartments separated by a gas-permeable membrane, with the blood on one side and the ventilating gas on the other. It was originally used exclusively in newborns but is now being used more and more in adults.

high pressure oxygenation (hyperbaric oxygenation (HBO)) see hyperbaric oxygenation.

pulsed oxygenation a technique by which oxygen is delivered to the patient only during inhalation rather than continuously during the respiratory cycle; used to conserve oxygen in patients using chronic low-flow oxygen therapy at home.

transtracheal oxygenation a technique of oxygen administration for patients requiring chronic oxygen therapy, in which oxygen is administered at low flow through a catheter passing directly into the trachea. This may be more cosmetic for patients and may require a lower flow of oxygen than other methods such as the use of a nasal cannula.

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extracorporeal membrane oxygenation

A form of artificial oxygenation of blood, in which a cannula in the jugular vein is connected to a small reservoir, into which the blood drains by gravity; the blood is then pumped from the reservoir through a membrane oxygenator and heat exchanger, and returned to the Pt via the right carotid artery cannula; ECMO is part of the surgical repair of congenital diaphragmatic hernia in infants, and is standard therapy for many full-term infants with poor lung function; it has had limited success in older children and adults