A comparison of the efficacy and cardiorespiratory effects of four medetomidine-based anaesthetic protocols in the red fox (Vulpes vulpes)

Abstract

ObjectiveTo evaluate the anaesthetic and cardiorespiratory effects of four anaesthetic protocols in red foxes (Vulpes vulpes). Study designProspective, blinded and randomized complete block design. AnimalsTen adult captive red foxes. MethodsFoxes were anaesthetized by intramuscular (IM) injection using four protocols in random order: medetomidine 40 μg kg−1, midazolam 0.3 mg kg−1 and butorphanol 0.1 mg kg−1 (MMiB), medetomidine 40 μg kg−1 and ketamine 4 mg kg−1 (MK40/4), medetomidine 60 μg kg−1 and ketamine 4 mg kg−1 (MK60/4), medetomidine 40 μg kg−1 and tiletamine/zolazepam 2 mg kg−1 (MTZ). Time to lateral recumbency, induction time and time to recovery following IM administration of atipamezole 0.2 mg kg−1 were recorded. Heart rate (HR), respiratory rate (fR) and rhythm, blood pressure, rectal temperature, end-tidal CO2 tension (Pe′Co2), functional oxygen saturation and presence/absence of interdigital, palpebral and ear reflexes were recorded every 10 minutes, and following administration of atipamezole. Data were analysed using two-way repeated-measures anova with Bonferroni post tests; p < 0.05 was considered significant. ResultsAll protocols produced profound sedation with good muscle relaxation. Only the MMiB protocol diverged significantly from the others. Induction of anaesthesia and recovery time following atipamezole were significantly longer, and fR and initial HR significantly lower with MMiB than with the other protocols. With all protocols, mean arterial blood pressure (MAP) was initially relatively high (140–156 mmHg), and decreased significantly over time. With all protocols, the administration of atipamezole resulted in a rapid, significant decrease in MAP and an increase in HR. Conclusions and clinical relevanceAll four protocols provided anaesthetic conditions suitable for minor procedures and allowed endotracheal intubation. The cyclohexanone protocols provided quicker and more reliable inductions and recoveries than the MMiB protocol.