Extracorporeal membrane oxygenation
Extracorporeal membrane oxygenation (ECMO) is a procedure that uses an artificial heart-lung machine to take over the work of the lungs (and sometimes 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.
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 the following problems:
- 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 and/or intestines through an opening in the diaphragm.
- Blood poisoning
- Inborn errors of metabolism: Some genetic diseases.
ECMO is also used to support a child's damaged, infected, or failing lungs for a few hours to allow treatment or healing. It is effective for those children with severe, but reversible, heart or lung problems who have not responded to treatment with a ventilator, drugs, or extra oxygen. Children who need ECMO usually have one of the following problems:
- immature or underdeveloped lungs
- heart failure
- respiratory failure caused by trauma or severe infection
- status asthmaticus (severe asthma attack)
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.
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 child is stable on ECMO, the breathing machine settings are lowered to "rest" settings, which allows the lungs to rest without the risk of too much oxygen or pressure from the ventilator.
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 child'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 child. 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 is 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.
Before ECMO is begun, the patient receives medication to ease pain and restrict movement.
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. Some infants may have difficulty feeding after ECMO treatment.
Bleeding is the biggest risk for ECMO patients, since blood thinners (most often heparin) 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 children undergoing ECMO.
If bleeding becomes a problem, the patient may require frequent blood or platelet transfusions or operations to control the bleeding. If the bleeding cannot be stopped, ECMO is 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, nurse, or respiratory therapist.
Normal results include the lungs and/or heart returning to healthy functioning while on ECMO treatment.
ECMO is used only for severely ill children. Parents need to talk with the nurse and doctor on a daily basis for updates on the condition of the child. The child may appear slightly swollen.
When to call the doctor
Notify a doctor if the child on ECMO is not behaving as expected (sedated and quiet), appears less pink (or bluer than normal), or is bleeding.
Carotid artery —One of the major arteries supplying blood to the head and neck.
Congenital diaphragmatic hernia —A profusion of part of the stomach through an opening in the diaphragm that is present at birth.
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 pressure in the blood vessels of 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 extracorporeal membrane oxygenation 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 extracorporeal membrane oxygenation that provides lung support only, using a tube inserted into the jugular vein.
Cohen, Margaret, et al. Sent Before My Time: A Child Psychotherapist's View of Life on a Neonatal Intensive Care Unit. London: Karnac Books, 2003.
American Society of Extra-Corporeal Technology. 503 Carlisle Dr., Suite 125, Herndon, VA 20170. Web site: http://www.amsect.org.
ECMO Moms and Dads. Rt. 1, Box 176AA, Idalou, TX 79329. Web site: http://www.medhelp.org/amshc/amshc341.htm.
Extracorporeal Life Support Organization. 1327 Jones Dr., Ste. 101, Ann Arbor, MI 48105. Web site: http://www.elso.med.umich.edu.
Mark A. Best Carol A. Turkington