Changes in the EEG during castration in horses and ponies anaesthetized with halothane.
Abstract: To identify changes in the amplitude spectrum of the electroencephalogram (EEG) during a standardized surgical model of nociception in horses. Methods: Thirteen entire male horses and ponies referred to Division of Clinical Veterinary Science, Bristol (n = 9) and Department of Clinical Veterinary Medicine (n = 4) for castration. Methods: Following pre-anaesthetic medication with acepromazine, anaesthesia was induced with guaiphenesin and thiopental and maintained with halothane in oxygen. The EEG was recorded continuously using subcutaneous needle electrodes. Additional monitoring comprised ECG, arterial blood pressure, blood gas analysis, airway gases, and body temperature. All animals were castrated using a closed technique. The raw EEG was analysed after completion of each investigation and the EEG variables median frequency (F50), spectral edge frequency (SEF) 95% and total amplitude were derived from the spectra using standard techniques. The mean values of EEG variables recorded during a baseline time period (recorded before the start of surgery) and castration of each testicle were compared using analysis of variance for repeated measures. Results: Total amplitude (Atot) decreased and F50 increased during castration of each testicle compared to the baseline time period [(89.0 +/- 7.8% testicle 1, 87.0 +/- 7.8% testicle 2) and (110.0 +/- 15.0% testicle 1, 109.0 +/- 15.0% testicle 2), respectively]. Changes in SEF 95% were not significant. Conclusions: De-synchronization was identified in the EEG during the nociceptive stimulus of castration. The results suggest that an increase in F50 may be a specific marker for nociception in the horse. Conclusions: Studies investigating the efficacy of analgesic agents in horses are limited by difficulties in peri-operative pain assessment. This model, using EEG changes associated with nociceptive stimulation, can be used to investigate the anti-nociceptive efficacy of different anaesthetic agents in the horse.
Publication Date: 2003-09-23 PubMed ID: 14498845DOI: 10.1046/j.1467-2995.2003.00138.xGoogle Scholar: Lookup
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- Journal Article
Summary
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This research studied changes in the electroencephalogram (EEG) of horses during the pain-causing process of castration with the aim of identifying specific markers for pain detection in the horse.
Objective
The main goal of this research was to identify changes in the electrical activity of the horse brain (measured by EEG) during a standardized surgical model of pain induction in horses (castration). The investigation aimed to determine if there were specific markers that could indicate the presence of pain in horses, as determined during anaesthesia.
Methods
- Thirteen male horses and ponies set for castration were involved in the study.
- The horses were anaesthetized using acepromazine, guaiphenesin, thiopental, and then maintained on halothane throughout the procedure.
- The EEG was recorded continuously using subcutaneous needle electrodes placed over their brains.
- Other health indicators including ECG, arterial blood pressure, blood gases, airway gases, and temperature were also monitored.
- Once the recording was over, the raw EEG data was analysed, with focus on median frequency (F50), spectral edge frequency (SEF) 95% and total amplitude as key variables.
Results
- The researchers found that during castration, total EEG amplitude decreased while the F50 frequency increased as compared to baseline pre-operative readings.
- Interestingly, there were no significant changes in the spectral edge frequency (SEF) 95% during the process.
- These shifts in EEG readings indicated a clear EEG de-synchronization during the pain-causing stimulus of castration.
Conclusions
- The outcomes suggest that an increase in F50 may be a reliable marker for pain detection in horses.
- Due to the lack of techniques for assessing pain in horses, this research provides a promising method that uses EEG changes associated with pain-causing stimulus to measure the efficacy of different pain relieving (analgesic) agents in these animals.
Cite This Article
APA
Murrell JC, Johnson CB, White KL, Taylor PM, Haberham ZL, Waterman-Pearson AE.
(2003).
Changes in the EEG during castration in horses and ponies anaesthetized with halothane.
Vet Anaesth Analg, 30(3), 138-146.
https://doi.org/10.1046/j.1467-2995.2003.00138.x Publication
Researcher Affiliations
- Department of Clinical Sciences of Companion Animals, University Utrecht, Faculty of Veterinary Medicine, PO Box 80154, NL-3508 TD, Utrecht. J.C.Murrell@vet.uu.nl
MeSH Terms
- Anesthetics, Inhalation
- Animals
- Electroencephalography / veterinary
- Halothane
- Horses / physiology
- Horses / surgery
- Male
- Orchiectomy / methods
- Orchiectomy / veterinary
- Pain Measurement / methods
- Pain Measurement / veterinary
Citations
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