Sedative and cardiopulmonary effects of dexmedetomidine infusions randomly receiving, or not, butorphanol in standing horses.
Authors: Medeiros Luíza Quintão, Gozalo-Marcilla Miguel, Taylor Polly M, Campagnol Daniela, de Oliveira Flávia Augusta, Watanabe Marcos Jun, de Araujo Aguiar Antonio José
Journal: The Veterinary record
Summary
# Editorial Summary Dexmedetomidine administered as a constant rate infusion (CRI) is increasingly used for standing sedation in horses, but optimal dosing protocols remain unclear, particularly when combined with opioids. This randomised, blinded crossover study compared sedative efficacy and safety of dexmedetomidine alone (3.5 µg/kg bolus plus 5 µg/kg/hour CRI) versus dexmedetomidine combined with butorphanol (3.5 µg/kg plus 3.5 µg/kg/hour and 20 µg/kg plus 24 µg/kg/hour respectively) in six healthy horses, measuring head height reduction, ataxia, responsiveness to stimuli, and cardiopulmonary parameters over 90 minutes of infusion and 60 minutes post-infusion. Both protocols produced comparable sedation with maximum head lowering of approximately 54–58% at 15 minutes, though ataxia and reduced tactile responses lasted only 15 minutes and auditory responses remained suppressed for up to 60 minutes; critically, clinically adequate sedation was achieved for just 30 minutes regardless of butorphanol inclusion. Cardiopulmonary effects typical of α₂-agonists (bradycardia, hypertension) occurred with both regimens, showing no significant difference between treatments. For practitioners selecting a standing sedation protocol, these findings suggest that neither dexmedetomidine monotherapy nor the addition of butorphanol at these doses provides sufficient duration for extended procedures, indicating that either repeated boluses, higher infusion rates, or alternative combinations may be necessary for procedures exceeding 30 minutes.
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Practical Takeaways
- •If using dexmedetomidine infusions for standing sedation, expect only 30 minutes of clinically adequate sedation; plan procedures accordingly or consider repeated boluses/alternative protocols
- •Adding butorphanol to dexmedetomidine does not extend duration of sedation or alter cardiopulmonary safety profile at these doses, so choice between regimens should be based on analgesia requirements rather than sedation duration
- •Monitor for ataxia in the first 15 minutes and plan handling accordingly; horses will be responsive to stimuli again after 30-60 minutes
Key Findings
- •Maximum head height reduction occurred at 15 minutes in both DEX (54%) and DEX/BUT (58%) groups, with ataxia lasting 15 minutes
- •Both treatments provided clinically sufficient sedation for only 30 minutes despite continuous infusion
- •Responses to tactile/auditory stimuli were reduced for 30 minutes in both treatments, with auditory suppression extending to 60 minutes in DEX alone
- •No significant cardiopulmonary differences were observed between DEX and DEX/BUT treatments, with typical alpha-2 agonist effects present in both