PSI-34 Painful and impractical: how to refine calf anesthesia.

摘要

A common sedation procedure in veterinary practice is intramuscular injection of xylazine. However, recent research has shown that intramuscular (IM) injections are more aversive than subcutaneous (SC) and intra-nasal (IN) routes. The first aim of the current study was to assess the relative efficacy of xylazine sedation using these alternative routes. The effects of sedatives are usually estimated through physiological parameters, which can be impractical to apply on farm. Thus a second aim was to estimate how well a simple behavior assessment of depth of sedation is associated with different physiological parameters. Using a within-subject design, we assessed the effects of xylazine (0.2mg/kg) sedation in 12 young Holstein calves (6.2 ± 2.8d) when administered via IM, SC, IN drip tube (INt) and IN spray (INs). All calves received each route, with treatment order pseudo randomized and allowing 48h between treatments. Sedation was behaviorally assessed on a 0–5 scale based on general state of the animal and eyeball rotation. Heart rate (HR), respiratory rate (RR) and rectal temperature (RT) were recorded for 2 hours after treatment. Calves sedated through the IM and SC routes had equivalent latencies to induction (mean±SD. IM:4.8 ± 2.0min; SC:6.8 ± 2.2min) and duration of sedation (IM:60.3 ± 25.5min; SC:61.9 ± 23.3min). During IN treatments calves showed less consistent and longer induction times (INt:33.0 ± 26.9min; INs:31.0 ± 15.1min) and shorter durations of sedation (INt: 42.0 ± 31.5 min; INs: 26.7 ± 21.8 min). The sedation scores were well correlated (repeated measures correlations with 95% CI) with HR (r=-0.55; CI -0.63, -0.47) but less so with RR (r=-0.34; CI -0.43,-0.24), and RT (r =-0.14, CI -0.24, -0.04). We conclude that the subcutaneous route is a viable alternative and recommend its use to avoid more aversive intramuscular injections. We also conclude that a simple clinical scale can be used to assess sedation and this measure is associated with some physiological parameters used for the same purpose.