Perioperative Brain Function Monitoring with Electroencephalography in Horses Anesthetized with Multimodal Balanced Anesthetic Protocol Subjected to Surgeries.
Authors: Murillo Carla, Weng Hsin-Yi, Weil Ann B, Kreuzer Matthias, Ko Jeff C
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary Monitoring brain activity during equine surgery remains challenging, yet understanding perioperative consciousness levels could improve anaesthetic management and recovery outcomes. Researchers used electroencephalography (EEG) to track cortical activity in 12 horses receiving a balanced multimodal protocol—xylazine and butorphanol premedication, ketamine/midazolam/guaifenesin induction, and isoflurane maintenance—measuring the Patient State Index (PSI), burst suppression ratio and spectral edge frequency across four stages from induction through post-operative recovery. The PSI dropped significantly during surgery (20.8 ± 2.6) compared to early recovery (30.0 ± 27.7, p = 0.005), whilst burst suppression increased markedly from induction (5.5%) to early recovery (32.7%, p = 0.0001), indicating profound central nervous system depression that persisted even after isoflurane discontinuation. Notably, EEG patterns revealed substantial delta wave activity (0.1–4 Hz) during early recovery and a continued reduction in faster frequency bands (3–7 Hz) after xylazine redosing, demonstrating unexpected residual CNS depression post-anaesthesia. For equine practitioners, these findings suggest EEG could serve as a practical tool for optimising anaesthetic depth and identifying when horses are genuinely ready for extubation and recovery, potentially reducing perioperative complications associated with inadequate or excessive anaesthetic levels.
Read the full abstract on PubMed
Practical Takeaways
- •EEG monitoring can provide real-time objective assessment of brain state changes throughout equine anesthesia, potentially improving anesthetic management
- •Recovery period shows significant brain activity changes that warrant careful monitoring; xylazine sedation during recovery causes profound CNS depression beyond anesthetic cessation
- •PSI and spectral analysis parameters offer quantifiable endpoints for assessing adequacy of anesthesia and recovery quality in horses undergoing surgery
Key Findings
- •Patient State Index (PSI) was lowest during surgery (20.8 ± 2.6) and increased significantly during early recovery (30.0 ± 27.7, p = 0.005)
- •Burst Suppression Ratio increased from induction (5.5 ± 10.7%) to early recovery (32.7 ± 33.8%, p = 0.0001), indicating increased brain suppression
- •Early recovery showed significantly higher delta wave activity (0.1-4 Hz) and lower power in 3-15 Hz range compared to induction and surgical stages
- •Xylazine sedation during recovery further increased central nervous system depression despite isoflurane cessation, with reduced power in 3-7 Hz range