Seeking to improve the care of preterm infants, a new study by researchers at Rutgers Robert Wood Johnson Medical School has found a more accurate test for jaundice, a common disorder in newborns. Jaundice in preterm infants is caused by the elevation of bilirubin, an orange-yellow substance in the blood that is not properly processed by the infant's immature liver. The problem also occurs in term infants. If not treated effectively, excess bilirubin can cause severe neurological damage and death. The study was published today in The Journal of Pediatrics.
There are two types of bilirubin: total, which binds to a substance in the blood allowing it to be easily excreted from the body, and unbound, which flows freely within the blood not connected to any substance. As a result, unbound bilirubin is capable of crossing the blood brain barrier and inducing brain toxicity. In preterm infants who show signs of jaundice, it is standard practice to test for total serum bilirubin, in order to plan a course for treatment. According to the researchers, however, measuring solely for the level of unbound bilirubin would more accurately determine the risk of neurotoxicity.
"Preterm infants are given an intravenous fatty emulsion called Intralipid, to provide nutrition and calories," said Thomas Hegyi, MD, professor of pediatrics at Robert Wood Johnson Medical School and principal investigator of the study. "However, in the race to bind to compounds in the blood the free fatty acids within the emulsion take precedence, leaving an elevated level of unbound bilirubin, which is potentially toxic, particularly in extremely low birth weight preterm infants. Therefore, changing the diagnostic tools to test for unbound bilirubin would provide more accurate treatment interventions and better protection against neurological injury."
In addition, the researchers found that the ability to metabolize the free fatty acids and the resulting amount of unbound bilirubin is highly variable among premature newborns. The standard test for total serum bilirubin, therefore, can not be utilized to predict the unbound bilirubin level and potential for neurological impairment.
The standard treatment for jaundice in preterm infants along with Intralipid, is phototherapy or treatment with a light, which is absorbed through the skin and helps the body break down the free moving bilirubin so it may be easily eliminated. Looking forward, Dr. Hegyi said that continued research will focus on comparing the neurodevelopmental outcome of preterm infants whose treatment with phototherapy and the emulsion will be determined by either the measurement of the current standard of testing the total serum bilirubin or the measurement of only unbound bilirubin.
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