Kernicterus was found in 20 infants autopsied between Jan ′72 and June ′77 at Kings County Hospital-Downstate Medical Center. Most of the infants were very premature; mean gestational age was 31.5(27-37)wks with mean birth weight of 1430(670-2910)g. Age at death ranged from 41 hrs. to 5 mos. with a median of 130 hrs. Peak serum bilirubin values ranged from 6.5 to 20.6 mg% (mean, 11.5mg%). Only 2 infants had values greater than 15mg%; both of these infants received exchange transfusion and 11 others had phototherapy.
Since the bilirubin levels were so low, we analyzed the clinical and laboratory features which may have contributed to the development of kernicterus. Hypoalbuminemia (<2.5%) was found in 6/9. In 4 of 5 infants in whom HABA dye binding studies were done, the values were very low (<25%). Anemia was present in all infants with evidence of hemolysis in 9/14. Internal bleeding was found in all, including 15/20 cases of intracranial hemorrhage. Respiratory distress with acidosis and hypoxia was present in all cases. There was evidence of infection in 13/20 infants. A greater proportion of the larger (≥1950g) infants had infection (5/6) than did the smaller infants (8/14). Although most of the infants did not exhibit all the classical signs of kernicterus clinically, they did have evidence of non-specific CNS involvement such as apnea, bradycardia and cardiorespiratory arrest.
On the basis of these findings, it is difficult to define a safe level of serum bilirubin below which kernicterus cannot occur. It would appear that in infants with extreme prematurity, infection, acidosis and hypoxia, we must either find a mean of preventing even modest bilirubin accumulation or a new index to assess the state of bilirubin diffusibility.