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Mark Hydak MD, Guest Editor
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Jaundice and Kernicterus
Hyperbilirubinemia and Kernicterus: 50 Years Later: Commentary. Ip S et al. PEDIATRICS (July 2004); 114: 264-265
There is no doubt that bilirubin plays a major role in the development of central nervous system pathology. High-quality studies have consistently demonstrated abnormal brainstem auditory evoked responses to elevated serum bilirubin levels. Indirect evidence from the decreasing prevalence of kernicterus since the introduction of Rhogam and prophylactic use of phototherapy also implicates hyperbilirubinemia as a major factor associated with kernicterus. However, >50 years after the report by Hsia et al, the premise that hyperbilirubinemia alone is sufficient to explain kernicterus is still not entirely satisfactory. In our review of 123 cases of kernicterus in infants greater than 34 weeks’ gestation published between 1955 and 2001, 88 had comorbid factors such as hemolysis, sepsis, and other neonatal complications. It was not possible to separate the effects of these comorbid factors from hyperbilirubinemia to further elucidate the chain of events leading to kernicterus. We concluded that hyperbilirubinemia, in most cases, is a necessary but not sufficient condition to explain kernicterus. Epidemiologic studies are useful to evaluate factors associated with disease outcome, but they offer inadequate proof for causation. In this era of low prevalence of erythroblastosis fetalis, measurement of TSB remains invaluable in the management of infants with jaundice. Treating hyperbilirubinemia will likely prevent kernicterus in most instances. However, this also implies that we need to treat many jaundiced infants to prevent 1 from developing kernicterus. To illustrate, let us assume for the moment that the incidence of kernicterus is somewhere between 1 in 100,000 to 1 in 1,000,000 newborns and that 2% of the million newborns per year have TSB levels of 20 mg/dL. If we further assume that kernicterus only occurs with a TSB level of 20 mg/dL, then we will treat anywhere between 2,000 and 20,000 newborns to prevent 1 case of kernicterus. TSB alone is a poor indicator of kernicterus risk. We need to explore the use of newer tools in conjunction with TSB to target infants at higher risk. Kernicterus is rare, but it is not extinct. As a preventable tragedy, it remains a highly controversial issue. Much work remains to be done to understand its pathophysiology and optimize its prevention.
Comments: This commentary speaks for itself. The pendulum for the approach to, and the treatment of, hyperbilirubinemia begins to swing back. Twenty-one years after the publication of Watchko and Oski's "Vigintiphobia", in-hospital phototherapy will undergo a resurgence. Many more infants will be treated to prevent a single case of kernicterus. Will these guidelines generate increased pressure on FDA to outline a clear pathway for the approval of tin protoporphyrin as a universal prophylactic treatment for hyperbilirubinemia? Personally, I think that is unlikely in the near future as I expect the FDA will take a wait and see approach as data becomes available on whether these systematic changes in surveillance will in fact effect a dramatic decrease in kernicterus. MH
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