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Electroencephalographic Power Spectrum Analysis as a Monitor of Anesthetic Depth in Horses
Author(s) -
OTTO KLAUS,
SHORT CHARLES E.
Publication year - 1991
Publication title -
veterinary surgery
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.652
H-Index - 79
eISSN - 1532-950X
pISSN - 0161-3499
DOI - 10.1111/j.1532-950x.1991.tb01284.x
Subject(s) - electroencephalography , anesthetic , medicine , amplitude , anesthesia , halothane , spectral density , spectral analysis , nuclear magnetic resonance , physics , mathematics , optics , statistics , spectroscopy , quantum mechanics , psychiatry
Electroencephalographic (EEG) power spectrum analysis was performed in 18 conscious, adult horses for evaluation as control values for EEG data obtained during anesthesia. Computer‐processed total amplitudes for the frequency range 0 to 32 Hz were mainly between 400 and 600 μV, with 80% spectral edge frequency between 16.6 and 32.5 Hz. The highest electrical activity was in the delta band (41.3 ± 4.4% of total amplitude); there was a less pronounced activity in the beta (34.2 ± 5.2%), theta (13.6 ± 1.5%), and alpha (10.0 ± 1.0%) bands. The applicability of EEG power spectrum analysis as a guide to depth of anesthesia was evaluated in four horses by comparing simultaneously recorded EEG data and clinical signs of anesthesia. Global changes in cerebrocortical electrical activity were detected with a single, monopolar (left frontoatlanto‐occipital) EEG lead. Increasing depth of halothane anesthesia was accompanied by a pronounced shift in EEG activity from beta to theta and delta frequency bands, a decrease in 80% spectral edge frequency from 21.5 ± 2.4 Hz to 12.6 ± 2.2 Hz, a reduction in the beta/delta ratio of fractional amplitudes from 2.37 ± 0.84 to 0.49 ± 0.04, and a slight inconsistent increase in total amplitude from 96.1 ± 37.3 μV to 185.5 ± 53 μV. These results show that changes in the clinical signs of anesthetic depth in horses can be described numerically by use of EEG power spectrum analysis.