This substance is then filtered by the kidneys and excreted in the urine. The liver can only convert a limited amount of bilirubin, so if blood levels become too high, the bilirubin begins to settle in the body tissues, producing the characteristic yellow skin of jaundice . Bilirubin also has an affinity for brain tissue where it can accumulate and cause permanent brain damage. 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.
The wavelength of the light interacts with the bilirubin and converts it into another substance that is excreted back into the bloodstream and exits with the feces without requiring additional conversion in the kidneys. For phototherapy treatment the newborn is placed nude under the fluorescent lights with eyes and genitalia covered. 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. Depending on the cause of jaundice full recovery is usually expected.