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Home / Equine Research Bank / J Vet Intern Med / Electroencephalogram of Healthy Horses During Inhaled Anesth...
Journal of veterinary internal medicine2015; 30(1); 304-308; doi: 10.1111/jvim.13613

Electroencephalogram of Healthy Horses During Inhaled Anesthesia.

Abstract: Previous study of the diagnostic validity of electroencephalography (EEG) to detect abnormalities in equine cerebral cortical function relied on the administration of various drugs for sedation, induction, and maintenance of general anesthesia but used identical criteria to interpret recordings. Objective: To determine the effects of 2 inhalation anesthetics on the EEG of healthy horses. Methods: Six healthy horses. Methods: Prospective study. After the sole administration of one of either isoflurane or halothane at 1.2, 1.4, and 1.6 times the minimum alveolar concentration, EEG was recorded during controlled ventilation, spontaneous ventilation, and nerve stimulation. Results: Burst suppression was observed with isoflurane, along with EEG events that resembled epileptiform discharges. Halothane results were variable between horses, with epileptiform-like discharges and bursts of theta, alpha, and beta recorded intermittently. One horse died and 2 were euthanized as the result of anesthesia-related complications. Conclusions: The results of this study indicate that the effects of halothane and isoflurane on EEG activity in the normal horse can be quite variable, even when used in the absence of other drugs. It is recommended that equine EEG be performed without the use of these inhalation anesthetics and that general anesthesia be induced and maintained by other contemporary means.
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: 2015-09-16 PubMed ID: 26376458PubMed Central: PMC4913644DOI: 10.1111/jvim.13613Google Scholar: Lookup
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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.

This research investigates the effects of two inhalation anesthetics, isoflurane and halothane, on electroencephalogram (EEG) readings in healthy horses. The study suggested that the effects were quite variable, with complications leading to the demise of three animals, thus recommending that equine EEG be performed without these anesthetics.

Objective of the Study

  • The study aimed to examine the impact of two anesthetics, isoflurane and halothane, on the EEG readings in healthy horses. This was done to determine if they affect the reading of the cerebral cortical function and if they can be safely used in equine medical practice.

Research Methodology

  • The researchers conducted a prospective study involving six healthy horses.
  • Each horse received either the isoflurane or halothane anesthetic, given at 1.2, 1.4, and 1.6 times the minimum alveolar concentration. This was done to evaluate the effects on EEG at varying intensities of the anesthetic.
  • The EEG was recorded during controlled ventilation, spontaneous ventilation, and nerve stimulation. This allowed for the observation of how these procedures influence EEG readings under the effect of the anesthetics.

Results of the Study

  • The results noted that burst suppression was observed with isoflurane, including EEG events that appeared similar to epileptiform discharges. This suggests that the use of isoflurane could lead to irregular EEG readings.
  • Halothane’s results varied between horses, with discharges resembling epileptiform, and bursts of theta, alpha, and beta intermittently recorded. Hence, ambiguity was present in the effects of halothane.
  • Unfortunately, one horse died, and two more were euthanized due to complications from anesthesia, reflecting the potential adverse effects of these anesthetics.

Conclusions of the Study

  • The study concluded that the effects of isoflurane and halothane on EEG activity in horses can be highly inconsistent even when used in the absence of other drugs.
  • Given the variability and adverse outcomes observed, the study recommended performing equine EEG without the use of these particular inhalation anesthetics.
  • The researchers suggest inducing and maintaining general anesthesia by other, safer means for EEG procedures in equine practice.

Cite This Article

APA
Williams DC, Aleman MR, Brosnan RJ, Fletcher DJ, Holliday TA, Tharp B, Kass PH, Steffey EP, LeCouteur RA. (2015). Electroencephalogram of Healthy Horses During Inhaled Anesthesia. J Vet Intern Med, 30(1), 304-308. https://doi.org/10.1111/jvim.13613

Publication

Journal of veterinary internal medicine
ISSN: 1939-1676
NlmUniqueID: 8708660
Country: United States
Language: English
Volume: 30
Issue: 1
Pages: 304-308

Researcher Affiliations

Williams, D C
  • William R. Pritchard Veterinary Medical Teaching Hospital, School of Veterinary Medicine, University of California, Davis, CA.
Aleman, M R
  • Departments of Medicine and Epidemiology, School of Veterinary Medicine, University of California, Davis, CA.
Brosnan, R J
  • 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.
Holliday, T A
    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.
    Steffey, E P
    • Surgical and Radiological Sciences, School of Veterinary Medicine, University of California, Davis, CA.
    LeCouteur, R A
    • 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
    • Reproducibility of Results

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    Citations

    This article has been cited 9 times.
    1. Figueroa S, Levionnois OL, Mirra A. Quantitative Variables Derived from the Electroencephalographic Signal to Assess Depth of Anaesthesia in Animals: A Narrative Review. Animals (Basel) 2025 Aug 5;15(15).
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    2. Aleman M, Benini R, Elestwani S, Vinardell T. Juvenile idiopathic epilepsy in Egyptian Arabian foals, a potential animal model of self-limited epilepsy in children. J Vet Intern Med 2024 Jan-Feb;38(1):449-459.
      doi: 10.1111/jvim.16965pubmed: 38041837google scholar: lookup
    3. Williams DC, Haulena M, Dennison S, Waugh L, Goldstein T, Nutter F, Bonn BV, Hoard V, Laxer KD, Buckmaster PS, Gulland FMD, Tharp B. Pinniped electroencephalography: Methodology and findings in California sea lions (Zalophus californianus). Front Vet Sci 2023;10:1040125.
      doi: 10.3389/fvets.2023.1040125pubmed: 37065231google scholar: lookup
    4. Vinardell T, Elestwani S, Jamieson C, Karim E, Robin M, Glynn S, Benini R, Aleman M. Electroencephalographic evaluation under standing sedation using sublingual detomidine hydrochloride in Egyptian Arabian foals for investigation of epilepsy. J Vet Intern Med 2023 May-Jun;37(3):1209-1215.
      doi: 10.1111/jvim.16695pubmed: 37029498google scholar: lookup
    5. Murillo C, Weng HY, Weil AB, Kreuzer M, Ko JC. Perioperative Brain Function Monitoring with Electroencephalography in Horses Anesthetized with Multimodal Balanced Anesthetic Protocol Subjected to Surgeries. Animals (Basel) 2022 Oct 20;12(20).
      doi: 10.3390/ani12202851pubmed: 36290236google scholar: lookup
    6. Chincarini M, Dalla Costa E, Qiu L, Spinelli L, Cannas S, Palestrini C, Canali E, Minero M, Cozzi B, Ferri N, Ancora D, De Pasquale F, Vignola G, Torricelli A. Reliability of fNIRS for noninvasive monitoring of brain function and emotion in sheep. Sci Rep 2020 Sep 7;10(1):14726.
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    9. Tünsmeyer J, Hopster K, Kästner SB. Clinical Use of a Multivariate Electroencephalogram (Narcotrend) for Assessment of Anesthetic Depth in Horses during Isoflurane-Xylazine Anesthesia. Front Vet Sci 2016;3:25.
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