Comparison between dexmedetomidine and a combination of medetomidine-vatinoxan on muscle tissue saturation in privately-owned adult dogs undergoing intradermal testing

Abstract

This double-blinded randomized cross-over study compared the muscle tissue oxygen saturation (StO₂) measured at the sartorius muscle after intramuscular (IM) injection of dexmedetomidine hydrochloride (HCl) and co-administration of vatinoxan HCl, a peripheral α2-adrenoceptor antagonist, and medetomidine HCl in healthy privately-owned dogs undergoing intradermal testing (IDAT). After written owner consent, dogs received IM injections of either dexmedetomidine (0.5 mg/m², DEX) or medetomidine (1 mg/m²) and vatinoxan (20 mg/m²) (MVX). Once sedated, intradermal injections were given on the lateral thorax of each dog, and the study was repeated with the alternative sedation on the opposite side one week later. At the end of the study, sedation was reversed with atipamezole (5 mg/m²). Depth of sedation, cardiopulmonary parameters, StO₂, and rectal temperature were recorded and compared using mixed effect linear models (α ≤ 0.05). MVX achieved adequate sedation faster [median (interquartile range), 10 (8, 10) minutes] compared to DEX [18 (15, 22) minutes; hazard ratio = 7.44, p = 0.013), with higher scores at 10- and 15-min post-injection. StO₂ was significantly reduced for 30 min after injection (p < 0.001), independently of the treatment (p = 0.68). Cardiopulmonary variables favored MVX. However, higher heart rate did not correlate with improved StO₂. There was no difference in either subjective or objective assessment of the wheal size between sedations (p > 0.05). Both sedation protocols, MVX and DEX, were deemed suitable for IDAT in dogs, with mild reductions in StO₂ measured at the sartorius muscle that were not significantly different between treatments.

Keywords: Intradermal testing; Medetomidine; NIRS; StO(2); Vatinoxan.