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Journal of veterinary internal medicine2015; 30(1); 289-303; doi: 10.1111/jvim.13813

Qualitative and Quantitative Characteristics of the Electroencephalogram in Normal Horses during Administration of Inhaled Anesthesia.

Abstract: 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.
Copyright © 2015 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.
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Publication Date: 2015-12-30 PubMed ID: 26714626PubMed Central: PMC4913671DOI: 10.1111/jvim.13813Google Scholar: Lookup
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  • Clinical Trial
  • Journal Article
  • Research Support
  • Non-U.S. Gov't

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

The research article discusses the effects of inhaled anesthetics on the brainwaves (EEG) of horses. It compares the impact of two common anesthetics, isoflurane and halothane, and finds that while they influence EEG, they may not provide a significant advantage when monitoring the depth of anesthesia over more traditional methods like checking arterial pressure.

Objective of the Study

The main goal of this research was to examine the effects of two inhaled anesthetics – isoflurane and halothane and how they impact a horse’s electroencephalogram (EEG). This is important as there is a need to monitor the depth of anesthesia during veterinary procedures, and EEG is one potential measure for this.

  • Isoflurane and halothane were chosen as they are commonly used in veterinary medicine for anesthesia.
  • The study specifically looked at how these anesthetics affected the EEG when administered at different concentrations (1.2, 1.4 and 1.6 MAC).
  • A digital EEG was recorded with video and quantitative EEG (qEEG) before and after anesthetic administration. The segments were then compared.

Research Methods

Six healthy horses underwent this study and various physiological measures were recorded alongside EEG data.

  • The anesthetics were administered in a controlled environment and the EEG changes were recorded under three different conditions – controlled ventilation (CV), spontaneous ventilation (SV), and during peroneal nerve stimulation (ST).
  • EEG variability was evaluated not only between different horses but also within individual horses over time.
  • Other measurements taken during the study included changes in mean arterial pressure and heart rate.

Results

The results indicated that changes in the raw EEG data were linked to the depth of anesthesia.

  • However, the study showed important variability in EEG readings not only between different horses but also within the same horse over time. This casts doubts on the accuracy of using EEG as a single measure of anesthesia depth.
  • Different anesthetics also produced different changes in the qEEG values. Isoflurane altered the bispectral index (BIS) under controlled ventilation and 95% spectral edge frequency (SEF95) during spontaneous ventilation. Halothane mainly affected the median frequency (MED) during spontaneous ventilation.

Conclusion

The study’s findings suggest that while EEG features might help monitor the depth of anesthesia, they don’t offer significant advantages over conventional methods such as monitoring arterial pressure. This potentially limits the utility of EEG as a standalone anesthetic depth monitor.

Cite This Article

APA
Williams DC, Brosnan RJ, Fletcher DJ, Aleman M, Holliday TA, Tharp B, Kass PH, LeCouteur RA, Steffey EP. (2015). Qualitative and Quantitative Characteristics of the Electroencephalogram in Normal Horses during Administration of Inhaled Anesthesia. J Vet Intern Med, 30(1), 289-303. https://doi.org/10.1111/jvim.13813

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 30
Issue: 1
Pages: 289-303

Researcher Affiliations

Williams, D C
  • William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA.
Brosnan, R J
  • Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
Fletcher, D J
  • Section of Emergency and Critical Care, Cornell University, Ithaca, NY.
Aleman, M
  • Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA.
Holliday, T A
  • Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
Tharp, B
  • Department of Neurology, University of California Davis Medical Center, Sacramento, CA.
Kass, P H
  • Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, CA.
LeCouteur, R A
  • Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
Steffey, E P
  • Departments of Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.

MeSH Terms

  • Anesthesia, Inhalation / veterinary
  • Anesthetics, Inhalation / pharmacology
  • Animals
  • Cross-Over Studies
  • Electroencephalography / drug effects
  • Electroencephalography / veterinary
  • Halothane / pharmacology
  • Horses / surgery
  • Isoflurane / pharmacology

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Citations

This article has been cited 8 times.
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