The sedative effects of low-dose medetomidine and butorphanol alone and in combination intravenously in dogs.

OBJECTIVE: To evaluate the sedative effects of intravenous (IV) medetomidine (1 microg kg(-1)) and butorphanol (0.1 mg kg(-1)) alone and in combination in dogs. STUDY DESIGN: Prospective, blinded, randomized clinical trial. ANIMALS: Sixty healthy (American Society of Anesthesiologists I) dogs, aged 6.2 +/- 3.2 years and body mass 26 +/- 12.5 kg. METHODS: Dogs were assigned to four groups: Group S (sodium chloride 0.9% IV), Group B (butorphanol IV), Group M (medetomidine IV) and Group MB (medetomidine and butorphanol IV). The same clinician assessed sedation before and 12 minutes after administration using a numerical scoring system in which 19 represented maximum sedation. Heart rate (HR), respiratory rate, pulse quality, capillary refill time and rectal temperature were recorded after each sedation score assessment. Sedation scores, sedation score difference (score after minus score before administration) and patient variables were compared using one-way anova for normally distributed variables and Kruskal-Wallis test for variables with skewed distributions and/or unequal variances. Where significance was found, further evaluation used Bonferroni multiple comparisons for pair-wise testing. RESULTS: Breed, sex, neuter status, age and body mass did not differ between groups. Sedation scores before substance administration were similar between groups (p = 0.2). Sedation scores after sedation were significantly higher in Group MB (mean 9.5 +/- SD 5.5) than in group S (2.5 +/- 1.8) (p < 0.001), group M (3.1 +/- 2.5) (p < 0.001) and group B (3.7 +/- 2.0) (p = 0.003). Sedation score difference was significantly higher in Group MB [7 (0-13)] than in Group S [0 (-1 to 4)] (p < 0.001) and Group M [0 (0-6)] (p < 0.001). HR decreased significantly in Groups M and MB compared with Group S (p < 0.05). CONCLUSION AND CLINICAL RELEVANCE: Low-dose medetomidine 1 microg kg(-1) IV combined with butorphanol 0.1 mg kg(-1) IV produced more sedation than medetomidine or butorphanol alone. HR was significantly decreased in both medetomidine groups.