Relationship of serum bilirubin levels and hearing impairment in newborn infants

A comparison has been made between 39 infants with a birthweight of 1500 g or less and a bilirubinlevel of 240 μmol/l or above, born between January 1980 and December 1983 and 19 infants with the same criteria, born between January 1984 and December 1985. Eight of the 22 high risk and two of the 17 low risk infants were diagnosed to have sensorineural deafness (SND) during the first period and this was strongly associated with the duration of the hyperbilirubinaemia. During the second period, more active intervention for hyperbilirubinameia led to an increased number of exchange transfusions and a marked drop in the mean duration of hyperbilirubinaemia (> 240 μmol/l). None of the very low birth weight (VLBW) infants born in the second period have developed SND. To investigate the independent effect of hyperbilirubinamia on hearing, six low risk infants with bilirubin levels > 320 μmol/l were studied by serial auditory brainstem responses (ABR). Impairment of the ABRs was found in four infants, with further deterioration with the persistence of high bilirubin levels in two. Although recovery of hearing thresholds was noted in all infants with impaired ABRs, an absence of wave I was noted in three infants at 6 months of age, which could indicate damage to the auditory nerve-cochlear complex. These findings suggest that hyperbilirubinaemia in itself can have an adverse effect on hearing and that careful management of hyperbilirubinaemia may reduce the incidence of sensorineural deafness.