Understanding severe hyperbilirubinemia and preventing kernicterus: adjuncts in the interpretation of neonatal serum bilirubin.

The serum total bilirubin concentration at any point in time represents the amount of bilirubin being produced minus that being excreted. Hyperbilirubinemia develops when bilirubin production exceeds the body's capacity to excrete it, primarily by conjugation. When extreme, hyperbilirubinemia may lead to the development of free bilirubin, that form of bilirubin which may cross the blood-brain barrier and enter and damage the basal nuclei of the brain. This rare, though devastating complication, may result in irreversible bilirubin induced brain damage termed kernicterus. In this paper, adjuncts to the interpretation of the serum total bilirubin are discussed, with the purpose of singling out those few neonates in real danger of bilirubin encephalopathy. Interpretation of the serum total bilirubin should be performed in conjunction with factors unique to the particular infant being evaluated. Understanding the mechanisms and dangers of severe neonatal hyperbilirubinemia should facilitate recognition of an emergency situation and optimize the speed with which bilirubin testing is performed and blood for exchange transfusion prepared. Hyperbilirubinemia is a condition of major importance and a source of concern to all involved in the management of the newborn. Its prevention and management should be based on the recently revised American Academy of Pediatric guidelines, with special attention paid to neonates manifesting risk factors for kernicterus. Close cooperation between the clinical laboratory and the medical team managing the newborn is an essential component in the management of a hyperbilirubinemic baby.