Total intravenous anaesthesia with ketamine, medetomidine and guaifenesin compared with ketamine, medetomidine and midazolam in young horses anaesthetised for computerised tomography.
Authors: Pratt S, Cunneen A, Perkins N, Farry T, Kidd L, McEwen M, Rainger J, Truchetti G, Goodwin W
Journal: Equine veterinary journal
Summary
# Editorial Summary: TIVA drug combinations for equine CT scanning Midazolam and guaifenesin are both commonly used as infusion partners with ketamine and medetomidine for total intravenous anaesthesia in horses, yet their comparative efficacy had never been directly evaluated. Pratt and colleagues conducted a prospective, randomised, blinded crossover trial in 14 weanlings, administering both drug combinations on separate occasions during 50-minute CT procedures; cardiorespiratory stability, anaesthetic depth, and recovery quality were systematically assessed using composite scoring systems. Both protocols provided stable anaesthesia with minimal differences in cardiopulmonary variables and no difference in supplementary drug requirements, but the ketamine-medetomidine-midazolam (KMM) combination produced significantly superior recovery quality across all three assessment scales (composite score P<0.001, simple descriptive scale P<0.001, visual analogue scale P<0.001), with no difference in overall recovery time between groups. For practitioners undertaking non-invasive procedures in young horses, whilst guaifenesin remains a valid choice, midazolam offers a pharmacologically attractive alternative that delivers noticeably smoother, more controlled recoveries—a clinically meaningful advantage that may reduce stress on both horse and handlers during the post-anaesthetic period. The study's limitation to non-stimulating CT work suggests findings may not directly translate to surgical situations, warranting cautious interpretation when considering these protocols for more invasive procedures.
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Practical Takeaways
- •For CT scanning in young horses, ketamine-medetomidine-midazolam produces superior quality recoveries compared to ketamine-medetomidine-guaifenesin, though both maintain anaesthesia adequately
- •Both drug combinations maintain similar cardiorespiratory stability during anaesthesia, giving clinicians flexibility in choice based on availability and recovery requirements
- •If smoother, better-quality recovery is a priority for your cases, prefer the midazolam combination despite similar induction and maintenance profiles
Key Findings
- •No clinically relevant differences in cardiopulmonary variables or additional anaesthetic requirements between ketamine-medetomidine-guaifenesin (KMG) and ketamine-medetomidine-midazolam (KMM) groups during 50-minute infusions
- •Recovery times were similar between both treatment groups with no significant difference
- •Recovery quality was significantly better with KMM compared to KMG across all assessment scales (CSS, SDS, VAS; all P<0.001)
- •Midazolam is a suitable alternative to guaifenesin when co-infused with ketamine and medetomidine in young horses undergoing non-invasive procedures