Conjugated bilirubin can be filtered by the kidneys and excreted in the urine. In a newborn infant the still immature liver can only convert a limited amount of bilirubin into its conjugated form, so if blood levels of bilirubin become too high, the bilirubin begins to dissolve in the body tissues, producing the characteristic yellow eyes and yellow skin of jaundice . Bilirubin also has an affinity for brain tissue where it can accumulate and cause permanent brain damage if the levels become too high. In severe cases of hyperbilirubinemia where the newborn has a low birth weight , is less than 24 hours old, and has a high bilirubin level, an exchange transfusion is preferred over phototherapy. With very high bilirubin concentrations, regardless of the age and weight, an exchange transfusion is the best option.
Phototherapy involves the exposure of bare skin to intense fluorescent light.
Specific wavelengths of the light interact with the bilirubin breaking it into several non-toxic water soluble components that can be excreted in the urine and stool. For phototherapy treatment the newborn is placed, without clothes or in a small diaper, under the fluorescent lights with the eyes covered to protect them from the bright light. Body temperature, vital signs , duration of treatment, positioning of the bulbs, and the newborns responses are carefully noted. The child is turned frequently to maximize the effects of therapy. If a baby is stable, phototherapy can be used at home along with the daily visits of a nurse who can obtain a sample of blood for testing.