P&S Journal: Spring 1994, Vol.14, No.2
Extra-corporeal Membrane Oxygenation
By Robin Eisner
Part of the mission of a teaching hospital and tertiary care facility such as Columbia-Presbyterian Medical Center is to offer expertise and treatment other institutions lack. One example is treatment for infants born with potentially fatal respiratory disorders. Because resistance to blood flow in these babies' lungs is so high, the lungs are unable to deliver desperately needed oxygen to the tissues.
A life-saving treatment provided by Dr. Charles Stolar, professor of surgery in the division of pediatric surgery, and his colleagues at Babies & Children's Hospital is known as extra-corporeal membrane oxygenation (ECMO), an intensive care therapy that oxygenates the baby's blood outside the body and returns it to the circulation until the heart and lung recover.
Over the past 12 years, a multidisciplinary team of physicians from 11 divisions in surgery, pediatrics, and radiology has used ECMO to save the lives of about 100 infants. The ECMO center at Babies & Children's Hospital is one of 80 in the United States, the only facility that provides ECMO in the New York, New Jersey, and Connecticut area, and the referral center for more than 50 regional centers. A second ECMO bed was added in 1991.
Some babies need ECMO because they cannot make the placenta-to-air transition to get oxygen. For various reasons, their lungs have trouble relaxing as they should. Their pulmonary blood vessels frequently have a constricting muscle layer that prevents blood flow into the lungs. To compensate for the lack of oxygen, the babies' hearts beat abnormally fast but to no avail. In healthy infants, lungs unfurl and the muscle surrounding the blood vessels fades during birth, allowing breathing and easy acquisition of oxygen.
To treat an infant with ECMO, a surgeon places two tubes-one into the jugular vein and one into the carotid artery-on the right side of the baby's neck. The tubes are connected to the ECMO circuit. The technology is similar to adult heart bypass machines, but ECMO has been designed for many days of use rather than the few hours required by open heart surgery. The tube from the jugular vein takes unoxygenated blood and pumps it through a silicone membrane lung, where it gets oxygenated. The oxygenated blood is warmed and returned to the baby via the carotid artery. In some infants a single two-channeled tube, one for draining unoxygenated blood and one for returning oxygenated blood, is placed only in the jugular vein. As the baby improves in about a week, the amount of blood circulated through the ECMO system is decreased slowly because the lungs start performing more of their normal function. During this time, the outer muscular layer on their blood vessels disappears.
ECMO is used to treat conditions of persistent fetal circulation, such as respiratory distress syndrome, meconium aspiration syndrome (aspiration of meconium, the first intestinal discharges of the infant, during labor), and diaphragmatic hernia (in which the intestines are crowded into the chest because of a hole in the diaphragm). Before ECMO is initiated, Dr. Stolar and his staff counsel parents about the procedure's risk of causing neurological problems, which occur in about 15 percent of the babies. These deficits presumably occur because the brain lacks oxygen during a critical perinatal time. It is hard to determine whether the problems are caused by the condition that necessitated ECMO, by ECMO itself, or by a combination of factors. Generally, babies on ECMO at Babies & Children's Hospital have an 80 percent to 95 percent survival rate, depending on the condition that required ECMO. Without ECMO, these babies have an estimated mortality approaching 100 percent.
Initially an investigational therapy financed by the Charles Edison and Anya Funds, ECMO is now an accepted medical intervention. Recently, New York State gave ECMO a diagnosis-related group, meaning it is eligible for reimbursement. Since Dr. Stolar started working with ECMO in 1981, he has learned more about its use. A decade ago, for example, about 50 percent of diaphragmatic hernia cases needed ECMO; today only 25 percent need it. Such knowledge gained from treating these infants is shared with referring physicians to help them improve their skills at assessing critical cases that require expertise of P&S faculty. ECMO usage is also part of training for pediatric surgical fellows, seven of whom now head ECMO programs throughout the United States.
Dr. Stolar hopes, though, that with enough research he and his colleagues can obviate the need for ECMO. "It is important for doctors not to be wedded to a particular therapy," he says. "The history of medicine is littered with out-of-date treatments. We aim to know enough someday to make ECMO obsolete."