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Korean Journal of Anesthesiology 1996;31(3):324-329.
DOI: https://doi.org/10.4097/kjae.1996.31.3.324   
EEG Spectral Analysis during Administation of Combined Inhalation Anesthetics in Rats.
Woon Yi Baek
Department of Anesthesiology, Kyungpook National University College of Medicine, Taegu, Korea.
The electroencephalogram(EEG) has long been used to study the effects of anesthetic drugs on central nervous system function. This study was designed to evaluate the accuracy of two EEG parameters for assessing anesthetic depth during inhalation of 1.5 MAC three inhalation anesthetics (halothane, enflurane, and isoflurane) with 50%-N2O in rats.
Total 15 rats weighing between 300~350 g, with 5 rats for each anesthetic group were tested for investigation the anesthetic depth. EEG spectrum analysis was evaluated for three inhalation anesthetics which all were added with 50%-N2O. The spectral edge frequency(SEF), median power frequency(MPF) were obtained from the EEG spectrum analysis of raw EEG via fast Fourier transform(FFT).
Raw EEG of halothane demonstrated sigmoidal shaped EEG, enflurane abundant spike waves, and isoflurane burst suppression. When 50%-N2O was added to each anesthetic group, the characteristics of the raw EEG were disappeared. EEG spectrum analysis enabled to distinguish the effects of each anesthetic on the anesthetic depth. EEG spectrum analysis demonstrated after 50%-N2O was added that the values of MPF and SEF were significantly decresed as 2.5 Hz and 6.5 Hz from 5.2 Hz and 14.2 Hz respectively.
It is speculated that SEF and MPF was decreased due to the suppression of cerebral electrical activity. The decreases of SEF and MPF from analysis of EEG spectra confirm that the addition of 50%-N2O to each inhalation anesthetics enabled the deeper anesthetic depth.
Key Words: Anesthetics; gases nitrous oxide; Anesthetics; volatile halothane; enflurane; isoflurane; Monitoring electroencephalography


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