Effects of acepromazine and dexmedetomidine, followed by propofol induction and maintenance with isoflurane anaesthesia, on the microcirculation of Beagle dogs evaluated by sidestream dark field imaging: an experimental trial.

OBJECTIVE: To investigate the effects of intramuscularly administered acepromazine or dexmedetomidine on buccal mucosa microcirculation in Beagle dogs. STUDY DESIGN: Experimental, blinded, crossover study. ANIMALS: A group of seven Beagle dogs aged 7.5 ± 1.4 years (mean ± standard deviation). METHODS: Microcirculation was assessed on buccal mucosa using sidestream dark field videomicroscopy. After baseline measurements, 5 µg kg-1 dexmedetomidine or 30 µg kg-1 acepromazine were administered intramuscularly. After 10, 20 and 30 minutes, measurements were repeated. At 40 minutes after premedication, anaesthesia was induced with propofol intravenously and maintained with isoflurane. Measurements were repeated 50, 60 and 65 minutes after the injection of the investigated drugs. Analysed microcirculatory variables were: Perfused de Backer density, Perfused de Backer density of vessels < 20 µm, Proportion of perfused vessels and Proportion of perfused vessels < 20 µm. Heart rate (HR), systolic, diastolic (DAP) and mean (MAP) arterial pressures were recorded at the same time points. Macro- and microcirculatory variables were analysed using a linear mixed model with baseline as a covariate, treatment, trial period and repetition as fixed effects and time and dog as random effect. Results are presented as effect size and confidence interval; p values < 0.05 were considered significant. RESULTS: After acepromazine, Perfused de Backer density was greater during sedation and anaesthesia [3.71 (1.93-5.48 mm mm-2, p < 0.0001) and 2.3 (0.86-3.75 mm mm-2, p < 0.003)], respectively, than after dexmedetomidine. HR was significantly lower, whereas MAP and DAP were significantly higher with dexmedetomidine during sedation and anaesthesia (p < 0.0001 for all) compared with acepromazine. CONCLUSIONS AND CLINICAL RELEVANCE: The sedative drugs tested exerted a significant effect on buccal mucosal microcirculation with a higher Perfused de Backer density after the administration of acepromazine compared with dexmedetomidine. This should be considered when microcirculation is evaluated using these drugs.