Follow-up study of auditory brainstem responses in hyperbilirubinemic newborns treated with exchange transfusion

Changes in auditory brainstem responses (ABR) were studied and followed in hyperbilirubinemic newborns before and after exchange transfusion (ET), in order to check their usefulness in the early detection of acute and chronic bilirubin encephalopathy. ABR were measured in 10 newborns with marked hyperbilirubinemia (total bilirubin concentration [TBC] > or = 20 mg/dL, direct bilirubin concentration < 2 mg/dL) before and after ET. The means of birthweight, gestational age, and day of life on admission were 3267 g, 38.2 weeks and 3.4 days, respectively. The ABR measurements were performed before ET and 6.0 days (the mean) after the ET. The follow-up of ABR was performed at 3 months of life. In comparison with the control values, the mean latencies of ABR were significantly prolonged (I, I-III, and I-V: P < 0.05) and the mean amplitudes were significantly decreased (I, III and V: P < 0.001) before ET. Significant improvement of ABR was noticed after the ET, especially in the shortening of the latency of wave I (P < 0.02) and in increasing the amplitudes of wave III and V (P < 0.02 and (P < 0.01, respectively), though the recovery of the latency of I-V (P < 0.02) and the amplitudes of I, III and V wave (P < 0.001, P < 0.001 and P < 0.01, respectively) were delayed in comparison to the control. The follow-up data of ABR showed that, in two of nine infants (one was lost from the follow-up), there were still abnormal findings at 3 months of age. Only one of these, who prolonged the recovery of ABR until 5 years of age, developed a border intelligence. Though ET is effective for improvement of acute bilirubin encephalopathy with impaired ABR, a complete recovery of the ABR might be delayed in marked hyperbilirubinemia. The delay in improvement of ABR abnormalities might be possibly used as an early predictor for following chronic bilirubin encephalopathy.