OBJECTIVE To evaluate effects of the peripherally acting α2-adrenoceptor antagonist MK-467 on cardiopulmonary function in sheep sedated with medetomidine and ketamine. ANIMALS 9 healthy adult female sheep. PROCEDURES Each animal received an IM injection of a combination of medetomidine (30 μg/kg) and ketamine (1 mg/kg; Med-Ket) alone and Med-Ket and 3 doses of MK-467 (150, 300, and 600 μg/kg) in a randomized blinded 4-way crossover study. Atipamezole (150 μg/kg, IM) was administered 60 minutes later to reverse sedation. Cardiopulmonary variables and sedation scores were recorded, and drug concentrations in plasma were analyzed. Data were analyzed with a repeated-measures ANCOVA and 1-way ANOVA. Reference limits for the equivalence of sedation scores were set at 0.8 and 1.25. RESULTS Heart rate, cardiac output, and Pao2 decreased and mean arterial blood pressure, central venous pressure, and systemic vascular resistance increased after Med-Ket alone. Administration of MK-467 significantly alleviated these effects, except for the decrease in cardiac output. After sedation was reversed with atipamezole, no significant differences were detected in cardiopulmonary variables among the treatments. Administration of MK-467 did not significantly alter plasma concentrations of medetomidine, ketamine, norketamine, or atipamezole. Sedation as determined on the basis of overall sedation scores was similar among treatments. CONCLUSIONS AND CLINICAL RELEVANCE Concurrent administration of MK-467 alleviated cardiopulmonary effects in sheep sedated with Med-Ket without affecting sedation or reversal with atipamezole.

OBJECTIVE To determine whether walking at specific ranges of absolute and relative (V*) velocity would aid efficient capture of gait trial data with low ground reaction force (GRF) variance in a heterogeneous sample of dogs. ANIMALS 17 clinically normal dogs of various breeds, ages, and sexes. PROCEDURES Each dog was walked across a force platform at its preferred velocity, with controlled acceleration within 0.5 m/s2. Ranges in V* were created for height at the highest point of the shoulders (withers; WHV*). Variance effects from 8 walking absolute velocity ranges and associated WHV* ranges were examined by means of repeated-measures ANCOVA. RESULTS The individual dog effect provided the greatest contribution to variance. Narrow velocity ranges typically resulted in capture of a smaller percentage of valid trials and were not consistently associated with lower variance. The WHV* range of 0.33 to 0.46 allowed capture of valid trials efficiently, with no significant effects on peak vertical force and vertical impulse. CONCLUSIONS AND CLINICAL RELEVANCE Dogs with severe lameness may be unable to trot or may have a decline in mobility with gait trial repetition. Gait analysis involving evaluation of individual dogs at their preferred absolute velocity, such that dogs are evaluated at a similar V*, may facilitate efficient capture of valid trials without significant effects on GRF. Use of individual velocity ranges derived from a WHV* range of 0.33 to 0.46 can account for heterogeneity and appears suitable for use in clinical trials involving dogs at a walking gait.