Measurement of brain stem auditory evoked potentials (BAEP) and midlatency auditory evoked potentials (MLAEP) using a new monitor integrated module was compared with an established device. The aim of this study was to evaluate if the new system could replace the more inconvenient established technique.
Material and Methods
MLAEP and BAEP were obtained from 19 anesthetized male patients using the AEP-Module for Monitor S/5 [GE, Helsinki, Finland (S/5)] and Neuropack 4 mini [Nihon Kohden, Tokyo, Japan (Neuropack)]. Significance of different results was calculated by paired t test. Bias was estimated by Bland-Altman statistics.
Latencies of BAEP were significantly shorter and amplitudes of BAEP were significantly higher for Neuropack. Mean latencies of MLAEP (Pa and Nb) were not significantly different (Pa 44.1±4.4 ms vs. 41.9±5.4 ms/Nb 66.4±5.6 ms vs. 62.8±6.5 ms), but methods are not interchangeable owing to great variability (Pa −13.16 to 8.94 ms, Nb −19.15 to 11.79 ms).
BAEP recorded by S/5 cannot be used for diagnostic interpretation using generally accepted normal values, but can be used for examining changes during the monitoring period. Mean values of Pa and Nb were not significantly different, but values of the S/5 varied above and below the values of Neuropack such that the measurements could not be used for diagnostic interpretation. However, this did not reduce their usefulness for determining adequate hypnosis.