Effect of hypoxia on the auditory system of goat fetuses during extrauterine incubation.

Abstract

To investigate the effect of hypoxia on the auditory system in fetuses, we attempted to analyze the auditory brainstem response, the middle latency response, and changes of several physiological parameters of goat fetuses during extrauterine incubation. We conducted extrauterine incubation of five goat fetuses at around 127days of gestation (term = 148 days). Their physiological parameters, such as fetal heart rate, mean blood pressure, flow rate of carotid artery, as well as the auditory brainstem response and middle latency response, were recorded prior to and during hypoxia, and the two sets of data were compared with each other. In all five cases, the fetal heart rate decreased from 178 +/- 12.2 b.p.m. to 144 +/- 15.2 b.p.m. during hypoxia, while mean blood pressure and flow rate of carotid artery increased from 37.3 +/- 3.7 mmHg to 43.2 +/- 5.1 mmHg, and from 38.5 +/- 5.5mL/min to 47.0 +/- 5.1 mL/min, respectively. The latency of the auditory brainstem response's wave V and of the middle latency response's Pa wave elongated from 5.24 +/- 0.24 ms to 5.69 +/- 0.20 ms, and from 19.2 +/- 1.6 ms to 20.9 +/- 1.4 ms, respectively. Although fetal compensatory reactions, such as increases in mean blood pressure and flow rate of carotid artery during hypoxia were recognized, elongation of latency, and decrement of amplitude were observed in the auditory brainstem response and middle latency response. These results suggest that hypoxia itself influences the auditory system of the fetus.