Study aims to improve care of newborns with respiratory distress
Many parents count their blessings toward the end of a healthy, full-term pregnancy. Their baby has been able to develop fully and will soon make his or her long-awaited debut. However, in a small percentage of births, these seemingly healthy infants will soon be fighting for their lives or battling chronic lung disease.
In 10 percent to 20 percent of all births in the United States, the fetus discharges meconium, a dark greenish material that normally accumulates in the bowel during development, into the amniotic fluid before birth. Each year, approximately 26,000 newborn infants develop Meconium Aspiration Syndrome (MAS) after aspirating the meconium into their lungs. The meconium may create a pneumonia with inflammation that deactivates the lung's surfactant, which is a foamy fluid needed for expansion of the air sacs in the lungs.
Dr. Robert Castro, associate professor in the Division of Neonatology in the Department of Pediatrics, is leading the Health Science Center's participation in a nationwide study on a new drug and treatment technique for newborns suffering from MAS. The drug is called Surfaxin®. He and co-investigator, Dr. Alice Gong, also an associate professor of pediatrics, are performing the study at the Neonatal Intensive Care Unit (NICU) at University Hospital.
"We hope to establish a standard of care for newborns with MAS a guideline that can be used throughout the country," said Dr. Castro, who serves as a faculty attending physician in the NICU. "Although substantial research has been performed on lung problems associated with premature newborns, little has been done on term or post-term newborns suffering with MAS. Unlike premature infants who are lacking surfactant, these bigger babies have normal amounts, but now because they inhaled the meconium, the surfactant has been damaged and their lungs cannot work properly."
Meconium Aspiration Syndrome consists of progressive respiratory distress, hypoxia (a reduction of oxygen supply to tissue), hypercarbnia (an excess of carbon dioxide in the blood) and acidosis (a condition caused by excess retention of carbon dioxide in the body). Severe cases of MAS require mechanical ventilation and intensive respiratory therapy.
About 40 percent of all infants who are put on extrapulmonary cardiac bypass have MAS. Dr. Castro said infants with MAS often are treated with other unproven, experimental therapies, such as high-frequency ventilation or steroids.
"Despite advances in newborn care, MAS patients are at high risk for pulmonary and extrapulmonary disabilities, and 4 percent to 12 percent will die from this disorder. While the majority survive, they often have lifelong chronic lung disease. Some of the infants even suffer neurological disabilities because oxygen is cut off to the brain. By participating in this study of Surfaxin, we hope to prevent infants from dying or from suffering debilitating health problems or disabilities," he said.
Sponsored by Discovery Laboratories, the two-year study involves 20 centers across the United States. At the University Hospital NICU and other participating sites, a newborn is eligible for the study if he has MAS, is on a ventilator, is younger than 72 hours of age and has not received other types of therapy for MAS, Dr. Castro explained.
Newborns who qualify for the study receive a bronchoalveolar lavage with Surfaxin. During the lavage technique, the medicine is actually injected into the lung and then washed out through the breathing tube. Each lung is washed out twice. Although the lavage or washing out of the lung flushes out the meconium, it also leaves some of the medicine in the lung to continue the treatment, he said. "Surfaxin, which is an artificially derived surfactant, washes out the meconium present in the airways, removes inflammatory infiltrates present in the respiratory tract, and opens alveoli (air sacs) by increasing the amount of functional surfactant in the air spaces."
In a preliminary study of this technique using Surfaxin, the newborns experienced improved oxygen levels and were removed from the ventilators earlier. "The longer infants stay on the ventilators, the greater their chance of developing chronic lung problems," he added.
Dr. Castro said the new surfactant drug also is believed to have properties that may help decrease lung inflammation for babies suffering from other respiratory problems, such as bacterial or viral pneumonia.
While results of this study will benefit infants around the United States, Dr. Castro said it is of particular importance to certain South Texas populations in which MAS is more prevalent. In South Texas, a higher percentage of women have little or no prenatal care or develop maternal diabetes compared to other parts of the country, he explained.
"Infants are at greater risk for MAS if they are stressed in utero. Mothers with hypertension or diabetes who are term or post-term have fetuses more prone to stress. If a mother does not have prenatal care, there is a greater chance she could go two or three weeks past term before delivering. This is hard on the fetus. When a fetus is stressed either before or during labor, there is a greater chance it will pass and aspirate meconium," he said.
The rates of MAS are declining nationwide because of improved prenatal care, Dr. Castro said. "One of the reasons is that most pregnant women have weekly prenatal exams toward the end of their pregnancies. If the mother has health problems, the physician will intervene by inducing labor or performing a cesarean section. By doing this, the fetus may not become stressed and have the opportunity to develop MAS," he explained.
Medical advances in prenatal care and labor and delivery procedures have prevented a great number of infants from suffering from MAS. However, for those newborns whose first struggle is with this respiratory disorder, the work of Drs. Castro, Gong and many others around the country may one day give them a fighting chance to live a long, healthy life.