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Navarrete-Calvo R, Morgaz J, Ruíz-López P, Gómez-Villamandos RJ, Domínguez JM, Quirós-Carmona S, Granados MM. Evaluation of spectral entropy monitor with different concentrations of isoflurane in Horses. J Equine Vet Sci 2025; 147:105398. [PMID: 39988185 DOI: 10.1016/j.jevs.2025.105398] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2024] [Revised: 02/01/2025] [Accepted: 02/20/2025] [Indexed: 02/25/2025]
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 min 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.
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Affiliation(s)
- R Navarrete-Calvo
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain
| | - J Morgaz
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain.
| | - P Ruíz-López
- Small Animal Department, School of Veterinary Medicine, Ghent University, Ghent, Belgium
| | - R J Gómez-Villamandos
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain
| | - J M Domínguez
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain
| | - S Quirós-Carmona
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain
| | - M M Granados
- Department of Animal Medicine and Surgery, School of Veterinary Medicine, Córdoba University, Rabanales University Campus, 14014, Córdoba, Spain
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Usefulness and Reliability of the Bispectral Index during Balanced Anesthesia for Neurovascular Surgery in New Zealand White Rabbits. Brain Sci 2023; 13:brainsci13020327. [PMID: 36831870 PMCID: PMC9954492 DOI: 10.3390/brainsci13020327] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Revised: 02/10/2023] [Accepted: 02/14/2023] [Indexed: 02/17/2023] Open
Abstract
Few data about the electroencephalogram and its calculated indices, such as the bispectral index (BIS), have been reported in rabbits. We aimed to evaluate whether a clinically stable anesthesia was mirrored by consistent and stable BIS values and to investigate the effects of modified cerebral blood supply, due to bilateral carotid clamping and re-opening, on BIS values. We also investigated the effects of fentanyl, as an antinociceptive drug, on the BIS. Sixty-eight rabbits undergoing general anesthesia for surgical creation of carotid bifurcation aneurysms were enrolled. The BIS values were recorded at nine selected time points (TPs) during each procedure and before and after fentanyl administration. The BIS values over time were compared with two-way repeated-measures analysis of variance followed by Tukey test, while the Wilcoxon signed rank test was performed to compare values at clamping and re-opening of the carotids as well as before and after fentanyl administration. The BIS values were significantly lower during anesthesia than at the end of anesthesia and at tracheal extubation; no significant differences were found among other TPs. Adequate depth of anesthesia was mirrored by consistent BIS values among rabbits, and alteration of cerebral blood supply did not modify BIS values, except once. Following fentanyl, BIS values did not change in a clinically relevant way.
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Perioperative Brain Function Monitoring with Electroencephalography in Horses Anesthetized with Multimodal Balanced Anesthetic Protocol Subjected to Surgeries. Animals (Basel) 2022; 12:ani12202851. [PMID: 36290236 PMCID: PMC9597736 DOI: 10.3390/ani12202851] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 10/07/2022] [Accepted: 10/18/2022] [Indexed: 11/29/2022] Open
Abstract
Simple Summary This study aimed to investigate the use of electroencephalography (EEG) and EEG-derived (processed) indices for detecting brain activity changes perioperatively in 12 anesthetized adult horses subjected to various surgery. Frontal electrodes together with Sedline/Root monitor were used on these horses from soon after anesthesia induction and continued until the horse first attempted to stand in recovery. The EEG waves were characterized by low-frequency high amplitude alpha, theta, and alpha waves during the isoflurane maintenance and surgery, which is commonly observed in profound anesthesia. The processed EEG indices including Patient State Index, Burst Suppression Ratio, and 95% Spectral Edge Frequency changed significantly between the stages (induction, surgery, and recovery) of anesthesia. Collectively, the presence of the slow EEG wave activities and the presence of burst suppression implies that these horses were profoundly unconscious during the anesthesia. We concluded that the use of EEG in conjunction with traditional cardiorespiratory monitoring provides clinically relevant information about perioperative brain state changes in the anesthetized horses. Abstract This study aimed to investigate the use of electroencephalography (EEG) for detecting brain activity changes perioperatively in anesthetized horses subjected to surgery. Twelve adult horses undergoing various surgeries were evaluated after premedication with xylazine and butorphanol, induction with ketamine, midazolam, and guaifenesin, and maintenance with isoflurane. The frontal EEG electrodes were placed after the horse was intubated and mechanically ventilated. The EEG data were collected continuously from Stage (S)1—transition from induction to isoflurane maintenance, S2—during surgery, S3—early recovery before xylazine sedation (0.2 mg kg IV), and S4—recovery after xylazine sedation. The Patient State Index (PSI), (Burst) Suppression Ratio (SR), and 95% Spectral Edge Frequency (SEF95) were compared across the stages. The PSI was lowest in S2 (20.8 ± 2.6) and increased to 30.0 ± 27.7 (p = 0.005) in S3. The SR increased from S1 (5.5 ± 10.7%) to S3 (32.7 ± 33.8%, p = 0.0001). The spectral power analysis showed that S3 had a significantly higher content of delta wave activity (0.1–4 Hz) in the EEG and lower relative power in the 3 Hz to 15 Hz range when compared to S1 and S2. A similar result was observed in S4, but the lower power was in a narrower range, from 3 Hz to 7 Hz, which indicate profound central nervous system depression potentiated by xylazine, despite the cessation of isoflurane anesthesia. We concluded that the use of EEG provides clinically relevant information about perioperative brain state changes of the isoflurane-anesthetized horse.
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