title: Qualitative and Quantitative Characteristics of the Electroencephalogram in Normal Horses during Administration of Inhaled Anesthesia.
abstract: 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.
  
  
  METHODS
  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 (SEF95) SV MAC differences in isoflurane only and median frequency (MED) differences in SV MAC with halothane only.
  
  
  CONCLUSIONS
  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.
authors.affiliation: William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: D C
authors.initials: DC
authors.lastname: Williams
authors.affiliation: Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: R J
authors.initials: RJ
authors.lastname: Brosnan
authors.affiliation: Section of Emergency and Critical Care, Cornell University, Ithaca, NY.
authors.forename: D J
authors.initials: DJ
authors.lastname: Fletcher
authors.affiliation: Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: M
authors.initials: M
authors.lastname: Aleman
authors.affiliation: Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: T A
authors.initials: TA
authors.lastname: Holliday
authors.affiliation: Department of Neurology, University of California Davis Medical Center, Sacramento, CA.
authors.forename: B
authors.initials: B
authors.lastname: Tharp
authors.affiliation: Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: P H
authors.initials: PH
authors.lastname: Kass
authors.affiliation: Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: R A
authors.initials: RA
authors.lastname: LeCouteur
authors.affiliation: Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
authors.forename: E P
authors.initials: EP
authors.lastname: Steffey
mesh_terms: D000769:Anesthesia, Inhalation / Q000662:veterinary*; D018685:Anesthetics, Inhalation / Q000494:pharmacology; D000818:Animals; D018592:Cross-Over Studies; D004569:Electroencephalography / Q000187:drug effects / Q000662:veterinary*; D006221:Halothane / Q000494:pharmacology*; D006736:Horses / Q000601:surgery*; D007530:Isoflurane / Q000494:pharmacology*
chemical_list: D018685:Anesthetics, Inhalation; D007530:Isoflurane; D006221:Halothane
keywords: bispectral index; halothane; isoflurane