Objective To compare the analgesic efficacy of buprenorphine plus detomidine with that of morphine plus detomidine when administered epidurally in horses undergoing bilateral stifle arthroscopy.
Study design Prospective, randomized, blinded clinical trial.
Animals Twelve healthy adult horses participating in an orthopedic research study. Group M (n = 6) received morphine (0.2 mg kg−1) and detomidine (0.15 mg kg−1) epidurally; group B (n = 6) received buprenorphine (0.005 mg kg−1) and detomidine (0.15 mg kg−1) epidurally.
Methods Horses received one of two epidural treatments following induction of general anesthesia for bilateral stifle arthroscopy. Heart rate (HR), mean arterial blood pressure (MAP), end-tidal CO2 (Pe′CO2), and end-tidal isoflurane concentrations (E′Iso%) were recorded every 15 minutes following epidural administration. Post-operative assessment was performed at 1, 2, 3, 6, 9, 12, and 24 hours after standing; variables recorded included HR, respiratory rate (fR), abdominal borborygmi, defecation, and the presence of undesirable side effects. At the same times post-operatively, each horse was videotaped at a walk and subsequently assigned a lameness score (0–4) by three ACVS diplomates blinded to treatment and who followed previously published guidelines. Nonparametric data were analyzed using Wilcoxon’s rank-sum test. Inter- and intra-rater agreement were determined using weighted kappa coefficients. Statistical significance was set at p ≤ 0.05.
Results No statistically significant differences were found between groups with respect to intra-operative HR, MAP, E′Iso%, or post-operative HR, gastrointestinal function and cumulative median lameness scores. Post-operative fR in group B [24 (12–30), median (range)] breaths per minute was significantly higher than in group M [18 (15–20)] breaths per minute, p = 0.04.
Conclusions and clinical relevance In horses undergoing bilateral stifle arthroscopy, these doses of buprenorphine plus detomidine injected epidurally produced analgesia similar in intensity and duration to that of morphine plus detomidine injected epidurally.