Background
Bilirubin is the lipophilic breakdown product of heme, which is responsible for oxygen transport in erythrocytes. It is bound to albumin in plasma and is glucuronidated in the liver by the UDP-glucuronosyltransferase UGT1A1 and excreted in bile. Conjugated bilirubin is more hydrophilic than lipophilic unconjugated bilirubin and can be eliminated from the body.
Symptoms
Physiologic neonatal jaundice manifests as yellowish skin and eyes of the newborn. It is very common and occurs in up to 60% of newborns in the first week of life.
Causes
The cause of jaundice is an increase in serum bilirubin to more than 5 mg/dL, which slowly decreases during the first week of life. The unconjugated bilirubin is deposited in the skin and mucous membranes. The reason for the bilirubin increase is due to the immature liver, the high heme concentration in newborns, and the renewed conversion of conjugated to unconjugated bilirubin in the intestine.
Complications
High bilirubin concentrations are toxic and can cause acute and permanent damage. If bilirubin levels rise too high, bilirubin can no longer be completely bound to albumin and passes across the blood–brain barrier into the brain, where it can damage the central nervous system (so-called “kernicterus,” bilirubin encephalopathy).
Diagnosis
Diagnosis involves medical treatment to rule out possible pathologic causes such as hemolytic disease, metabolic and endocrine disorders, infectious diseases, and anatomic abnormalities. Neonates at risk for severe hyperbilirubinemia should be identified.
Treatment
Phototherapy can be used to convert unconjugated bilirubin with light to the less toxic and water-soluble isomer lumirubin, which can be excreted unconjugated. The child is placed unclothed under the lamp to maximize body surface area. The eyes must be covered to protect them from damage by the light. With modern systems, no eye protection is necessary and the child can remain close to the mother (e.g. BiliBed). Blood exchange transfusion is available as a 2nd choice treatment. The following measures are recommended for prevention and treatment:
- Keep the child sufficiently warm
- Frequent breastfeeding
- Indirect exposure to sunlight
