Article (Scientific journals)
Ketamine increases the amplitude of the 40-Hz auditory steady-state response in humans
PLOURDE, Gilles; BARIBEAU, Jacinthe; BONHOMME, Vincent
1997In British Journal of Anaesthesia, 78 (5), p. 524-529
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Keywords :
Anaesthetic i.v.; Ketamine; Brain; Evoked potentials; Monitoring; Anesthesia; Depth
Abstract :
[en] The auditory middle latency response (AMLR) and the 40-Hz auditory steady-state response (40-Hz ASSR) are evoked potentials which possibly arise from the same generators in the primary auditory cortex. Both responses are attenuated by most general anaesthetics. Ketamine, however, has been reported to have no effect on the AMLR. Our aim was to evaluate the effects of ketamine on the 40-Hz ASSR. Spectral analysis of the electroencephalogram (EEG) was also conducted to independently examine the effects of ketamine. Ketamine 1.5 mg kg-1 was given to 12 patients for induction of general anaesthesia. Recordings of the 40-Hz ASSR and EEG were obtained every minute from 3 min before administration of ketamine to 5 min after injection, when the study was terminated. Similar recordings were obtained in three control subjects under identical conditions except that no medication was administered. Consciousness, defined as responsiveness to verbal commands, was assessed before each recording. Ketamine caused an increase in the amplitude of the 40-Hz ASSR (P < 0.01). Using published AMLR data, we conducted a simulation experiment that suggested that the effect of ketamine on the AMLR can explain its effects on the amplitude of the 40-Hz ASSR. There was a pronounced increase in relative theta (3.9-7.9 Hz) EEG power and a decrease in relative alpha (8.0-12.8 Hz) power (P < 0.001). These changes were not observed in the control group. Ketamine produced unconsciousness until the end of the study in five patients and transient unconsciousness in five patients. Two patients did not lose consciousness after administration of ketamine. The 40-Hz ASSR and EEG revealed no consistent differences between conscious and unconscious patients. No relationship could be demonstrated between the increase in amplitude of the 40-Hz ASSR or of relative theta power (the hallmark of ketamine effect) and loss of responsiveness to commands. We conclude that ketamine, unlike other anaesthetics, increases the amplitude of the 40-Hz ASSR.
Disciplines :
Anesthesia & intensive care
Author, co-author :
PLOURDE, Gilles;  McGill University - McGill > Anaesthesia
BARIBEAU, Jacinthe;  Concordia University > Psychology
BONHOMME, Vincent  ;  Centre Hospitalier Universitaire de Liège - CHU > Service médical d'anesthésie - réanimation
Language :
English
Title :
Ketamine increases the amplitude of the 40-Hz auditory steady-state response in humans
Publication date :
May 1997
Journal title :
British Journal of Anaesthesia
ISSN :
0007-0912
eISSN :
1471-6771
Publisher :
Oxford University Press, Oxford, United Kingdom
Volume :
78
Issue :
5
Pages :
524-529
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 11 August 2015

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