Evaluation of Spectral Entropy Monitor with Different Concentrations of Isoflurane in Horses.
Abstract: Spectral entropy and bispectral index (BIS) can differentiate between conscious and unconscious levels in horses. This study aimed to determine whether spectral entropy and BIS parameters can distinguish between different end-tidal isoflurane concentrations (EtIso, %), and whether these parameters change when a nociceptive stimulus is applied. Ten clinically healthy horses were anaesthetized using xylazine, diazepam, ketamine, and isoflurane. The following parameters were monitored: EtIso, response entropy (RE), state entropy (SE), RE-SE difference, BIS, and electromyography (EMG). Three EtIso concentrations were randomly assigned: 0.9% (EtIso0.9), 1.2% (EtIso1.2), and 1.5% (EtIso1.5). Ten minutes after reaching the first EtIso, the parameters were recorded at baseline (Baseline) and for 5 minutes following the application of an electrically nociceptive stimulus (first two minutes, EarlyP; the last three minutes, LateP). This procedure was repeated three times for each EtIso. A two-way repeated measures ANOVA was performed. The RE, SE, BIS, and EMG parameters exhibited a significant increase upon the application of a painful stimulus. Notably, only the EMG parameter demonstrated significant differences between EtIso0.9 and EtIs1.5 during both EarlyP and LateP phases (EarlyP: EtIso0.9, 72±23 vs EtIso1.5, 48 ± 23, (P=0.011); LateP: EtIso0.9, 65 ± 27 vs EtIso1.5, 43 ± 23, (P=0.022)). Currently, these monitors do not appear to be useful for assessing anaesthetic depth in horses under the studied conditions, although they do seem to be useful for detecting induced nociceptive stimuli.
Copyright © 2025. Published by Elsevier Inc.
Publication Date: 2025-02-21 PubMed ID: 39988185DOI: 10.1016/j.jevs.2025.105398Google Scholar: Lookup
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Summary
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The research investigates the effectiveness of spectral entropy and bispectral index to differentiate between consciousness levels in horses under different concentrations of Isoflurane anesthesia. The study finds that while both methods demonstrate an increase in response upon the introduction of a painful stimulus, they do not significantly distinguish between varying levels of Isoflurane concentration, leaving their usefulness in measuring anesthetic depth questionable.
Research Background and Objective
- Researchers aimed to assess how effective spectral entropy and bispectral index technologies can differentiate between varied isoflurane concentrations in the horse’s anesthetic process.
- They also wanted to determine if these parameters change in response to a nociceptive (pain-related) stimulus.
Experimental Procedure
- They worked with ten clinically healthy horses which were anaesthetized using a combination of xylazine, diazepam, ketamine, and isoflurane.
- Throughout the anesthesia process, they monitored parameters: end-tidal isoflurane concentrations (EtIso), response entropy (RE), state entropy (SE), the difference between RE and SE, bispectral index (BIS), and electromyography (EMG).
- Three randomly assigned concentrations of isoflurane were applied: 0.9%, 1.2%, and 1.5%.
- The monitoring parameters were recorded before and for five minutes after the application of an electrically induced painful stimulus.
Research Findings
- The results revealed a significant increase in response entropy, state entropy, bispectral index, and electromyography parameters upon the application of a painful stimulus.
- Of all the parameters, only the electromyography parameter demonstrated significant differences between 0.9% and 1.5% isoflurane concentrations during both early and late stages of pain stimulus.
- The study concluded that while spectral entropy and bispectral index monitors seem effective in detecting nociceptive stimuli, under the tested conditions, they proved ineffective in distinguishing different anesthetic depths in horses.
Implication of Research
- The result of this study indicates that spectral entropy and bispectral index monitors, in their current stage, may not be an optimal choice for assessing the depth of anesthesia in horses.
- The studies invite further research and development in these monitor technologies for better usefulness in anesthesia.
Cite This Article
APA
Navarrete-Calvo R, Morgaz J, Ruíz-López P, Gómez-Villamandos RJ, Domínguez JM, Quirós-Carmona S, Granados MM.
(2025).
Evaluation of Spectral Entropy Monitor with Different Concentrations of Isoflurane in Horses.
J Equine Vet Sci, 105398.
https://doi.org/10.1016/j.jevs.2025.105398 Publication
Researcher Affiliations
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain.
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain. Electronic address: v92moroj@uco.es.
- Small Animal Department, School of Veterinary Medicine, Ghent University, Ghent, Belgium.
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain.
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain.
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain.
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain.
Conflict of Interest Statement
Declaration of competing interest None of the authors has any financial or personal relationships that could inappropriately influence or bias the content of the paper.
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