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Equine veterinary journal2020; 52(5); 678-684; doi: 10.1111/evj.13234

Comparison of bispectral index and spectral entropy during isoflurane and medetomidine general anaesthesia in horses.

Abstract: The bispectral index (BIS) has been evaluated as an indicator of central nervous system (CNS) depression in horses during general anaesthesia. The spectral entropy is another electroencephalographic device and it has not been evaluated yet in horses. Objective: To determine if spectral entropy can assess anaesthetic depth during the different phases of anaesthesia, define the value of state and response entropy during surgical plane of anaesthesia and compare them with BIS. Methods: Clinical, prospective, non-blinded observational study. Methods: Thirty-five horses ASA I or II undergoing scheduled surgical procedure were used. BIS and electromyography (EMG) with a BIS monitor and state and response entropy with a spectral entropy monitor were recorded at baseline after receiving 5 µg/kg bwt i.v. of medetomidine (sedation period), during the anaesthetic maintenance with isoflurane and medetomidine (intraoperative period) and once the trachea was extubated (recovery period). A general linear model for repeated measurements was employed. Correlation and agreement between methods were also assessed. Data are presented as mean ± SD. Results: State entropy, response entropy and EMG showed significant differences according to the anaesthetic period (P < .001). There was no significant difference in BIS between baseline and sedation period, but there were differences between the remainder of the periods (P < .001). BIS (53.4 ± 11.2) was significantly higher (P < .001) than response entropy (35.1 ± 7.1) and state entropy (27.4 ± 4.8) during surgical plane of anaesthesia. The ICC between BIS and response entropy was 0.56 and between BIS and state entropy was 0.43, without agreement between them. Conclusions: The need to shave the skin in contact with the sensors and the difficulty in taking measurements during recovery period. Conclusions: Spectral entropy can be used to detect the different periods of an anaesthetic protocol, with the lowest values during the intraoperative period. A low correlation and no concordance were observed between both methods.
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Publication Date: 2020-02-21 PubMed ID: 31961457DOI: 10.1111/evj.13234Google 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 effectiveness of the spectral entropy (SE) method in assessing anaesthetic depth in horses during different stages of anaesthesia, compared to the bispectral index (BIS). It was found that while both methods demonstrate changes indicative of different stages of anaesthesia, BIS recorded higher indicators of consciousness during surgery than SE, without any agreement between the two methods.

Methods

  • The researchers conducted a clinical, prospective, non-blinded observational study of 35 horses in ASA physical status I or II, scheduled for surgical procedures.
  • The observational parameters included monitoring of BIS and electromyography (EMG) indicating muscle activity via a BIS monitor, in addition to state and response entropy via an SE monitor.
  • The observations were made at baseline (after administration of medetomidine), during anaesthetic maintenance with isoflurane and medetomidine (intraoperative period), and upon tracheal extubation (recovery period).

Results

  • During different stages of anaesthesia, significant variances were found in state entropy, response entropy, and EMG.
  • The BIS did not show any significant changes between the baseline and sedation period but displayed differences in the rest of the periods.
  • At the surgical plane of anaesthesia, the BIS was significantly higher than both response and state entropy.
  • Agreement between BIS and both subsystems of spectral entropy was limited. The Intraclass Correlation Coefficient (ICC) between BIS and response entropy was 0.56, and 0.43 with state entropy.

Conclusions

  • Complications of the study included the necessity to shave the skin for adequate sensor placement and the challenges involved in performing measurements during the recovery period.
  • Nonetheless, the study concluded that spectral entropy could be effectively used to identify different stages of an anaesthetic protocol, with minimum values recorded during the intraoperative stage.
  • The researchers noted that while both the BIS and SE indicated differences across the anaesthetic stages, they found low correlation and no concordance between the two methods, suggesting each may offer unique insight into the depth of anaesthesia.

Cite This Article

APA
Navarrete-Calvo R, Morgaz J, Gómez-Villamandos RJ, Quirós-Carmona S, Domínguez JM, Ruiz-López P, Granados MM. (2020). Comparison of bispectral index and spectral entropy during isoflurane and medetomidine general anaesthesia in horses. Equine Vet J, 52(5), 678-684. https://doi.org/10.1111/evj.13234

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 52
Issue: 5
Pages: 678-684

Researcher Affiliations

Navarrete-Calvo, Rocío
  • Department of Animal Medicine and Surgery, Veterinary Faculty, University of Cordoba, Córdoba, Spain.
Morgaz, Juan
  • Department of Animal Medicine and Surgery, Veterinary Faculty, University of Cordoba, Córdoba, Spain.
Gómez-Villamandos, Rafael J
  • Department of Animal Medicine and Surgery, Veterinary Faculty, University of Cordoba, Córdoba, Spain.
Quirós-Carmona, Setefilla
  • Department of Animal Medicine and Surgery, Veterinary Faculty, University of Cordoba, Córdoba, Spain.
Domínguez, Juan M
  • Department of Animal Medicine and Surgery, Veterinary Faculty, University of Cordoba, Córdoba, Spain.
Ruiz-López, Patricia
  • Department of Animal Medicine and Surgery, Veterinary Faculty, University of Cordoba, Córdoba, Spain.
Granados, María M
  • Department of Animal Medicine and Surgery, Veterinary Faculty, University of Cordoba, Córdoba, Spain.

MeSH Terms

  • Anesthesia, General / veterinary
  • Animals
  • Electroencephalography
  • Entropy
  • Horses
  • Isoflurane
  • Medetomidine
  • Prospective Studies

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This article includes 21 references
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Citations

This article has been cited 4 times.
  1. Petrucci M, Spadavecchia C, Wanderer S, Boillat G, Marbacher S, García Casalta LG, Casoni D. Usefulness and Reliability of the Bispectral Index during Balanced Anesthesia for Neurovascular Surgery in New Zealand White Rabbits. Brain Sci 2023 Feb 14;13(2).
    doi: 10.3390/brainsci13020327pubmed: 36831870google scholar: lookup
  2. 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
  3. Thorn CA, Wilson DV, Wang S, Horne WA. Impact of sequential administration of detomidine, butorphanol, and midazolam on sedation, ataxia, stimulus response, and bispectral index in horses. Front Vet Sci 2025;12:1691137.
    doi: 10.3389/fvets.2025.1691137pubmed: 41200548google scholar: lookup
  4. 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).
    doi: 10.3390/ani15152285pubmed: 40805076google scholar: lookup
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