Open AccessQualitative and Quantitative Characteristics of the Electroencephalogram in Normal Horses during Administration of Inhaled Anesthesia
Author(s) -
Williams D.C.,
Brosnan R.J.,
Fletcher D.J.,
Aleman M.,
Holliday T.A.,
Tharp B.,
Kass P.H.,
LeCouteur R.A.,
Steffey E.P.
Publication year - 2015
Publication title -
journal of veterinary internal medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.356
H-Index - 103
eISSN - 1939-1676
pISSN - 0891-6640
DOI - 10.1111/jvim.13813
Subject(s) - isoflurane , electroencephalography , medicine , halothane , anesthesia , anesthetic , minimum alveolar concentration , bispectral index , sedation , psychiatry
Background The effects of anesthesia on the equine electroencephalogram ( EEG ) after administration of various drugs for sedation, induction, and maintenance are known, but not that the effect of inhaled anesthetics alone for EEG recording. Objective To determine the effects of isoflurane and halothane, administered as single agents at multiple levels, on the EEG and quantitative EEG ( qEEG ) of normal horses. Animals Six healthy horses. Methods Prospective study. Digital EEG with video and quantitative EEG ( qEEG ) were recorded after the administration of one of the 2 anesthetics, isoflurane or halothane, at 3 alveolar doses (1.2, 1.4 and 1.6 MAC ). Segments of EEG during controlled ventilation ( CV ), spontaneous ventilation ( SV ), and with peroneal nerve stimulation ( ST ) at each MAC multiple for each anesthetic were selected, analyzed, and compared. Multiple non‐ EEG measurements were also recorded. Results Specific raw EEG findings were indicative of changes in the depth of anesthesia. However, there was considerable variability in EEG between horses at identical MAC multiples/conditions and within individual horses over segments of a given epoch. Statistical significance for qEEG variables differed between anesthetics with bispectral index ( BIS ) CV MAC and 95% spectral edge frequency ( SEF 95) SV MAC differences in isoflurane only and median frequency ( MED ) differences in SV MAC with halothane only. Conclusions and Clinical importance Unprocessed EEG features (background and transients) appear to be beneficial for monitoring the depth of a particular anesthetic, but offer little advantage over the use of changes in mean arterial pressure for this purpose.