Evaluation of the effects of commonly used α2-adrenergic receptor agonists alone and in combination with butorphanol tartrate on objective measurements of lameness in horses

Abstract

OBJECTIVE To determine the effects of 3 α2-adrenergic receptor agonists (α2-ARAs), alone or in combination with butorphanol tartrate, on objective measurements of lameness in horses. ANIMALS 17 adult polo horses with naturally occurring forelimb or hind limb lameness (or both). PROCEDURES In a crossover design, each horse received each protocol (saline [0.09% NaCl] solution [2 mL, IV] or xylazine hydrochloride [0.33 mg/kg, IV], detomidine hydrochloride [0.007 mg/kg, IV], or romifidine hydrochloride [0.033 mg/kg, IV] alone or in combination with butorphanol [0.007 mg/kg, IV]) in random order, with a washout period (≥ 7 days) between protocols. Horses were assessed immediately prior to (baseline) and 10, 15, 20, 30, and 40 minutes after administration of each protocol for degree of sedation, mechanical nociceptive threshold (MNT), and objective lameness measurements. RESULTS Compared with baseline values, sedation scores and MNTs were significantly higher at all evaluated time points following administration of all sedation protocols except xylazine alone; following administration of xylazine alone, sedation scores and MNTs were significantly higher at ≤ 30 minutes and ≤ 20 minutes, respectively. Significant differences in objective forelimb lameness measurements were noted after administration of the 3 α2-ARA-butorphanol combinations. Most significant differences in objective measurements of hind limb lameness were detected after administration of detomidine or romifidine, alone or in combination with butorphanol. CONCLUSIONS AND CLINICAL RELEVANCE In the study horses, xylazine alone had the least impact on objective lameness measurements. The administration of α2-ARAs, particularly detomidine or romifidine, alone or in combination with butorphanol, resulted in small but significant effects on objective lameness measurements.

Comparison of sedation quality and safety of detomidine and romifidine as a continuous rate infusion for standing elective laparoscopic ovariectomy in mares

“…Depth of sedation was objectively assessed using head height, as reported in previous studies 32‐34 . Across both treatment groups, there was a significant effect of time on all variables, regardless of treatment.…”

Can sedation be used for equine lameness investigation?

“…Buchner et al (1999) found that the use of detomidine did not alter forelimb lameness degree but did alter the general locomotory pattern. Likewise, the study by Moorman et al (2019) found no effect of detomidin on head movement asymmetry but did find a significant difference in pelvic movement asymmetry across all data points. They found no significant difference in head or pelvic movement asymmetry when using detomidine combined with butorphanol.…”

“…The use of detomidine hydrochloride was studied by Buchner et al (1999) and Moorman et al (2019). Buchner et al (1999) found that the use of detomidine did not alter forelimb lameness degree but did alter the general locomotory pattern.…”

“…The use of romifidine for lameness evaluations was only studied by Moorman et al (2019). Their results showed a significant difference in head movement asymmetry when horses had received romifidine in combination with butorphanol but showed no difference in pelvic movement asymmetry.…”

“…of 13found evidence to support the use of 2-agonists on their own for lameness investigation(De Cozar, 2019). Three clinical papers have since investigated the use of 2-agonists in combination with butorphanol(Beck Júnior et al, 2019;Moorman et al, 2019;and Morgan et al, 2020).Of the 2-agonists, xylazine is the most frequently studied. When looking at hindlimb lameness, Da Silva Azevedo et al(2015) found no significant difference in lameness degree after 5 minutes when using xylazine alone.Rettig et al (2016), Beck Júnior et al (2019) and Moorman et al (2019) found the same tendency up to 60, 40 and 40 minutes respectively.…”