Middle latency auditory evoked potential anaesthesia correlates of consciousness: Practicality & constraints

D. Burton, P. S. Myles, I. Brown, M. Xu, E. Zilberg

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The hypothesis of this study is that significant differentiation of consciousness (CO) and unconsciousness (UNCO) is possible, using individual ML+AEP (10-140 msec) latency measures, within the context of a practical routine clinical depth of anaesthesia monitoring device. We have assessed individual latency band measures of the middle-latency auditory evoked potential (ML+AEP) as candidates to measure depth of CO or UNCO amongst a group of anaesthetised surgical patients. We have also compared ML+AEP correlates with conventional auditory evoked potential (AEP) index and bispectral index (BIS). This study investigates amplitude measures, limits and the practicality of using a single EEG channel ML+AEP recording system. ML+AEP amplitude-related correlates were assessed against CO and UNCO events during anaesthesia. ML+AEP measures were computed for each of the following AEP component-related latency time bins (LTB): Na;15-25msec, Pa;25-35 msec, TP41;35-45 msec; Pb/P1;45-55 msec, N1;80-100 msec, <N1;0-80 msec, >N1;80-140 msec, and ML+AEP;0-140 msec. Twenty patients (aged 28-68 yrs) undergoing day surgery had their electroencephalography (EEG) monitored during binaural auditory stimulus presentation (6.8 clicks per second). The AEP grand mean waveform (AEP gmw) was computed for each consecutive stimulus AEP event, by way of averaging the previous 256 AEPs. The mean and SD amplitude associated with each of the ML+AEP ranges were computed for the whole study period and also for the predetermined events 1 to 13 (CO:1;2;3;12;13 and UNCO:4-11). Results included BIS data, measures derived from the AEPgmw across both the ML+AEP range (0-140 msec), and also individual LTB segments. For each respective AEP LTB the mean and SD for AEP power distribution (AEPPD) and AEP Differential analysis (AEPDA) was computed. Two-sample t-tests were performed in order to test the hypothesis that AEPDA and AEP pA indices measured across ML+AEP LTB (during surgical procedure) present significant differences between CO and UNCO. Significant (P<0.05) values were derived for all computed AEP LTB correlates, and also for all AEPPD LTB except Pa, TP41 and N1. Overall the P-values resulting from the application of the AEPDA method were much lower than those of the AEPPD method. Conclusion: While the practical limitations and constraints of AEP-based anaesthesia monitoring cannot be overlooked, individual AEP component-related correlates and particularly those related to waveform deflection or AEP Differential analysis (AEPDA) were shown to be candidates for depth of consciousness measures.

Original languageEnglish
Title of host publicationProceedings of the 2005 27th Annual International Conference of the Engineering in Medicine and Biology Society, IEEE-EMBS 2005
Number of pages7
Volume7 VOLS
Publication statusPublished - 2005
EventInternational Conference of the IEEE Engineering in Medicine and Biology Society 2005 - Shanghai, China
Duration: 1 Sep 20054 Sep 2005
Conference number: 27th
https://ieeexplore.ieee.org/xpl/conhome/10755/proceeding (Proceedings)


ConferenceInternational Conference of the IEEE Engineering in Medicine and Biology Society 2005
Abbreviated titleEMBC 2005
Internet address

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