Bilirubin Metabolism, Unconjugated Hyperbilirubinemia, and Physiologic Neonatal Jaundice
Neonatal jaundice is a frequent problem in neonatology, but with the advent of phototherapy which has simplified its treatment, it no longer represents a major concern, but early hospital discharge of neonates has now resulted in a re-emergence of the risk of kernicterus. Neonatal jaundice is principally the result of an increased synthesis of bilirubin, of a transient deficiency of bilirubin conjugation, of a partial deficiency of hepatic bilirubin uptake and intracellular transport, and of an increased enterohepatic circulation of the pigment that limit bilirubin elimination. The fact that bilirubin production in the neonate is two or more times greater than in the adult per kilogram of body weight represents the mainstay of this condition. Prevention of kernicterus in full-term infants is based on the detection of neonates at risk for developing hyperbilirubinemia. The daily evaluation of transcutaneous bilirubin measurement gives additional information on the rise of serum bilirubin level and can help to distinguish physiological from nonphysiological hyperbilirubinemia. A significant hyperbilirubinemia is more frequent in infants born before term and in neonates who do not feed well and lose more than 10% of body weight. Each jaundiced newborn should receive a bilirubin measurement. Transcutaneous bilirubin (TcB) can be used as first step in order to reduce the number of invasive and painful blood sampling, but TSB measurement is always necessary when the level of bilirubin is high and for therapeutic decisions.
Carboxyhemoglobin corrected for inspired CO
Total serum bilirubin
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