Neonatal Jaundice, Hyperbilirubinemia and Kernicterus
Most newborn infants develop a total serum or plasma bilirubin (TB) level of greater than 1 mg/dL. As the bilirubin level increases, it can produce neonatal jaundice. Jaundice is the yellowish discoloration of the skin and/or whites of the eyes caused by bilirubin deposition in the tissues.
Neonatal hyperbilirubinemia in newborn infants born at greater than or at 35 weeks gestational age is defined as a total serum or plasma bilirubin (TB) greater than the 95th percentile on the hour specific Bhutani nomogram (Figure1).
Hyperbilirubinemia can be caused by certain conditions or amplification of the processes responsible for neonatal jaundice. The most common cause of hyperbilirubinemia is increased production of bilirubin due to hemolytic diseases that include the following:
- Isoimmune – mediated hemolysis (e.g. ABO or Rh(D) incompatibility).
- Inherited red blood cell membrane defects.
- Erythrocyle enzymatic defects like glucose-6-erythropoietic dehydrogenase (G6PD) deficiency.
- Sepsis, and
- Breast feeding failure.
Severe neonatal hyperbilirubinemia is defined as a TB greater than 25 mg/dL. It is associated with an increased risk for the development of Bilirubin-Induced Neurologic Dysfunction (BIND) which happens when bilirubin crosses the blood-brain barrier and binds to brain tissue.
Acute Bilirubin Encephalopathy (ABE) is a term used to describe the acute manifestations of BIND which include: Sleepiness, lethargy, hypotonia, high-pitched cry, poor suck, irritability, arching of the back or trunk. Kernicterus is a term used to describe the chronic and permanent sequelae of brain damage caused by bilirubin toxicity.
Infants with kernicterus have movement disorders known as “dystonic” or “athetoid” cerebral palsy. The athetoid form of cerebral palsy refers to slow, writhing movements. Dystonia refers to abnormal muscle tone. Some children with kernicterus are deaf. Most infants and children with kernicterus are profoundly impaired and require lifelong care. Kernicterus is almost always preventable. The major risk factors for developing kernicterus are:
- Predischarge total serum or plasma bilirubin in the high-risk zone defined as greater than the 95th percentile for age.
- Jaundice within the first 24 hours of life.
- G6PD deficiency.
- Gestational age 35 to 36 weeks.
- Failure to recognize risk factors for developing hyperbilirubinemia.
- Failure to timely test bilirubin levels.
- Failure to treat hyperbilirubinemia.