Masters Theses

Date of Award

6-1983

Degree Type

Thesis

Degree Name

Master of Arts

Major

Audiology

Major Professor

Allan O. Diefendorf

Committee Members

Bob Moore

Abstract

Hyperbilirubinemia is associated with brain, central nervous system, and brainstem disorders. Premature low birth weight infants are at risk for damage at low levels of hyperbilirubinemia. Therefore, the need for an objective measure of early bilirubin toxicity is pronounced. A possible solution to this problem in the use of the auditory brainstem response (ABR). Based on evidence from previous studies, the ABR latency changes may follow bilirubin level changes in the premature low birth weight population.

The questions asked in this study were:

1. Is the ABR sensitive to changes in bilirubin levels, following the increases and decreases in bilirubin, in premature low birth weight infants? is the latency and bilirubin change relationship predictable and reliable?

2. If so, is the latency and bilirubin change relationship predictable and reliable?

ABR's to a 100 dB SPL click stimulus were obtained unilaterally from five premature infants, ranging in gestation age from 32 to 34 weeks and in birth weight from 1500 to 1870 grams, tested in 24 hour intervals from eight to fourteen consecutive days. The following ABR latencies were analyzed in relation to bilirubin levels: The infants were Wave I, Wave III, Wave III-V interwave intervals.

Basic trends in the latency-bilirubin change relationship were noted for Wave I, Wave III, and Wave I-III interwave intervals. Wave V, and Wave I-V, Wave I-III, and For four of the five subjects, consistent changes in bilirubin level in either direction resulted in systematic increases or decreases in the Wave III and Wave I-III interwave interval latencies for the first six At this point, the Wave III and Wave I-III interwave interval latencies stabilized and were independent of bilirubin changes.

Gestation age, birth weight, and respiratory distress did not to nine days of life. appear to be variables, while temporary conductive hearing loss appeared to be a possible explanation for Wave I latency shifts, intensity and bilirubin levels were possible factors influencing the outcome of the data. Stimulus The outcome of this study, demonstrating that the systematic Wave III latency-bilirubin changes relationship was observed for the first six to nine days of life only, supports the contention that the toxic effects of hyperbilirubinemia are most likely to occur during the first week of life. Because the Wave III latency changes followed bilirubin changes during this critical period, perhaps high (toxic) bilirubin levels may be monitored more objectively with the ABR.

Further research should deal with assessing the ABR in infants with bilirubin levels high enough to necessitate exchange transfusion, which may help to establish the toxic bilirubin level indicating exchange transfusion. Further study may also indicate that Wave III can be used to evaluate the premature infant population with greater accuracy and reliability.

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