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Middle latency auditory evoked potentials during repeated transitions from consciousness to unconsciousness
Author(s) -
DAVIES F. W.,
MANTZARIDIS H.,
KENNY G. N. C.,
FISHER A. C.
Publication year - 1996
Publication title -
anaesthesia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.839
H-Index - 117
eISSN - 1365-2044
pISSN - 0003-2409
DOI - 10.1111/j.1365-2044.1996.tb07694.x
Subject(s) - unconsciousness , anesthesia , medicine , consciousness , propofol , electroencephalography , audiology , heart rate , level of consciousness , electrophysiology , blood pressure , psychology , neuroscience , psychiatry
Summary We have investigated the relationship between changes in the middle latency auditory evoked potentials during alternating periods of consciousness and unconsciousness produced by propofol infusion combined with spinal anaesthesia for total knee replacement. Eleven patients completed the study, of whom two had recollection of events after the onset of the anaesthetic. There were no significant differences in heart rate or systolic arterial pressure between any conscious and unconscious period. With the first change from consciousness to unconsciousness, latencies of Na, Pa and Nb increased from mean (SD) starting values of 20.0 (1.4), 31.7 (1.0) and 42.8 (1.6)ms to 22.5 (2.0), 39.3 (2.1) and 57.8 (4.4)ms, respectively. During successive transitions from unconsciousness to consciousness, awake latencies were slightly higher than those of baseline awake, whereas anaesthetised latencies were similar to the ones obtained during the first period of unconsciousness. The consistent changes demonstrated, suggest that the auditory evoked potentials could represent a reliable indicator of potential awareness during anaesthesia.