Sedation with dexmedetomidine-butorphanol or xylazine-butorphanol continuous intravenous infusions during unilateral ovariectomy in standing donkeys

Background: Intravenous infusions of alpha-2 adrenoceptor sedatives and opioids can potentially facilitate surgery in donkeys while standing. Literature on this subject matter is scant.Objectives: Evaluation of efficacy of sedation from alpha 2-adrenoceptors (dexmedetomidine or xylazine) and butorphanol during ovariectomy in standing donkeys.Study design: Randomised, masked in vivo experiment.Methods: Thirteen female donkeys were sedated with butorphanol (0.05 mg/kg bwt followed by 0.5 mg/kg bwt/h) IV. Concomitantly, 6 of the 13 jennies were sedated with dexmedetomidine 2.5 mcg/kg bwt followed by 2.5 mcg/kg bwt/h (Dex-B group), while seven jennies were sedated with xylazine 0.5 mg/kg bwt followed by 0.5 mg/kg bwt/h (Xyl-B group). A line block of the left flank and an infiltration block around uterine ligament were performed with lidocaine. While the jennies underwent ovariectomies standing, sedation scores and head height above ground were assessed at 2 and 10 min after sedative boluses and every 10 min thereafter. If sedation was too light or too deep, the dose of dexmedetomidine or xylazine was increased or decreased by 25% of the original infusion rate, while butorphanol infusion rate was constant. Physiological parameters were measured. Normally distributed data were compared using the two-sample t test while repeatedly measured data were tested for differences between and within groups using repeated measures analysis of variance (ANOVA) by ranks followed by a Wilcoxon test with Tukey Honest Significant Difference for multiple testing. Statistical significance was set at p < 0.05.Results: Both Dex-B and Xyl-B caused moderate to marked sedation adequate for ovariectomy in donkeys. Evident sedation was absent by 60 min of termination of infusions. No adverse physiological effects were observed.Main limitations: Study on ovariectomy cases only, no pharmacokinetic profiling.Conclusions: Dexmedetomidine or xylazine and butorphanol sedation is feasible for ovariectomy in standing donkeys.