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An infant’s indirect (unconjugated) serum bilirubin level is elevated at 10 mg/dL. Unconjugated (indirect) bilirubin is the fraction of serum bilirubin that has not been conjugated with glucuronic acid in the liver. The exact definition of a physiologic range and management of indirect hyperbilirubinemia are complex and based on many factors, including gestational age (GA), postnatal age, birthweight, disease state, risk factors, ethnicity, and hydration and nutritional status. Total serum bilirubin (TSB) is the sum of direct (conjugated) and indirect (unconjugated) bilirubin. The indirect bilirubin is calculated by subtracting the direct bilirubin from the total bilirubin. Transcutaneous bilirubin (TcB) is a measurement of TSB from an instrument that uses reflectance measurements on the skin and correlates well with the laboratory TSB value. Unconjugated hyperbilirubinemia is usually transient and physiologic in the newborn period, but it is important to note that kernicterus (chronic bilirubin encephalopathy) is still occurring in the developed world.


  1. How old is the infant? What is the gestational age? High indirect serum bilirubin levels during the first 24 hours of life are never physiologic. Hemolytic disease (Rh isoimmunization or ABO incompatibility), infection, occult hemorrhage, and polycythemia are common causes of early-onset jaundice. GA and age in hours of the infant determine the bilirubin level at which phototherapy should be initiated. The risk of unconjugated hyperbilirubinemia is inversely proportional with GA. In premature infants, hyperbilirubinemia is usually more severe and lasts longer.

  2. Is the infant being breast fed? Breast-feeding jaundice (early onset) occurs within the first week of life and is secondary to decreased intake of breast milk resulting in dehydration and caloric deprivation. Breast milk jaundice (late onset) occurs after the first week of life and can last up to the third or fourth week. Current literature supports a genetic predisposition. High levels of the enzyme β-glucuronidase can also be a contributing factor leading to increased enterohepatic circulation.

  3. What is the family ethnicity? The incidence of neonatal jaundice is increased in infants of Native American Indian, Inuit, Mediterranean (Greece, Turkey, Sardinia), Sephardic Jewish, Nigerian, and Eastern Asian descent. Native Greeks have a higher incidence than Greeks in the United States. The incidence is lower in African Americans. Glucose-6-phosphate dehydrogenase (G6PD) deficiency, which is a cause of unconjugated hyperbilirubinemia, is more common in many of these groups and may be partially responsible. Immigration and intermarriage have increased the incidence of G6PD in the United States.

  4. Is the infant dehydrated? If evidence of dehydration exists (eg, weight loss of >12% from birthweight, increased sodium, decreased urine out), fluid administration may help to lower serum bilirubin level. Supplemental formula feedings or expressed breast milk should be considered if breast-feeding failure is the reason for hyperbilirubinemia; otherwise, intravenous (IV) fluids should be given. Adequate hydration is essential, but excess hydration by causing dilutional effects of IV fluids and enhancing peristalsis to decrease enterohepatic circulation by oral fluid supplements will not ...

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