The impact of vatinoxan on microcirculation after intramuscular co-administration with medetomidine in Beagle dogs: a blinded crossover study

Objective: To measure the effects on microcirculation of medetomidine alone (MED) or combined with vatinoxan (MVX). Study design: Randomized, crossover, blinded, experimental study. Animals: A group of eight healthy purpose-bred Beagle dogs. Methods: Each dog was administered 1 mg m–2 MED intramuscularly (IM) or combined with 20 mg m–2 vatinoxan IM (MVX) with a washout period of 7 days. A sidestream dark field (SDF) camera was placed on the buccal mucosa to assess the oral mucosal microcirculation for perfused DeBacker density, proportion of perfused vessels (PPV) (both for all vessels and vessels with a diameter < 20 μm), microvascular flow index (MFI) and heterogeneity index (HI). Videos were recorded at baseline (–5) and 10, 20, 30, 40, 60, 90 and 120 minutes after treatment administration. Linear mixed-effects models were used to assess if microvascular variables were significantly associated with treatment, baseline, and sequence. Results are presented as estimated effect (95% confidence interval), and a p value < 0.05 was considered significant. Results: The interquartile range for baseline measurements was 91.49%–98.42% for PPV, 2.75–3 for MFI and 0–0.36 for HI. Significant effects of treatment and baseline were found. The estimated effect of MED against MVX was –1.98% (–3.53% to –0.42%) for PPV, –0.33 (–0.43 to –0.22) for MFI and 0.14 (0.05 to 0.22) for HI. There were no significant changes seen for perfused DeBacker density, perfused DeBacker density < 20 μm and PPV < 20 μm between treatments. Conclusions and clinical relevance: These results suggest that MVX had significantly fewer effects on buccal mucosal microcirculation than MED. The SDF camera is a useful research tool to assess the microcirculatory status of heavily sedated dogs