Changes in the EEG power spectrum after midazolam anaesthesia combined with racemic or S- (+) ketamine.
Changes in the EEG power spectrum were studied in 50 patients (ASA status I or II), receiving either 2 mg.kg-1 of racemic ketamine or 1 mg.kg-1 of S-(+) ketamine in a randomized and double-blind manner after prior administration of 0.1 mg.kg-1 of midazolam. The patients receiving intramuscular premedication with midazolam about 45 minutes prior to induction of anaesthesia showed, in a deliberately quiet environment and mostly in the early morning, a delta dominated EEG (56% delta power) with a reduced alpha peak (17% alpha power) and an average median of 4 Hz as the baseline findings of the EEG power spectrum. The intravenous administration of midazolam led to activation of the lower beta range (13-18 Hz) and the subsequent injection of ketamine caused an increase in activity in the fast beta range (21-30 Hz), both being accompanied by a reduction of delta power from 56% to 40%. Correspondingly, an increase in the median frequency was noted. Causing nearly the same changes in EEG, S-(+) ketamine was confirmed to be twice as potent as racemic ketamine.
Hering
W
W
Department of Anaesthesiology, University of Erlangen-Nuernberg, Germany.
Geisslinger
G
G
Kamp
H D
HD
Dinkel
M
M
Tschaikowsky
K
K
Rügheimer
E
E
Brune
K
K
D000293:Adolescent; D000328:Adult; D000368:Aged; D000771:Anesthesia, Intravenous; D004311:Double-Blind Method; D004569:Electroencephalography / Q000187:drug effects*; D005260:Female; D006801:Humans; D007649:Ketamine / Q000494:pharmacology*; D008297:Male; D008874:Midazolam / Q000494:pharmacology*; D008875:Middle Aged
D007649:Ketamine; D008874:Midazolam