RESUMO
BACKGROUND: Intravenous infusions of alpha-2 adrenoceptor sedatives and opioids can potentially facilitate surgery in donkeys while standing. Literature on this subject matter is scant. OBJECTIVES: Evaluation of efficacy of sedation from α2-adrenoceptors (dexmedetomidine or xylazine) and butorphanol during ovariectomy in standing donkeys. STUDY DESIGN: Randomised, masked in vivo experiment. METHODS: Thirteen female donkeys were sedated with butorphanol (0.05 mg/kg bwt followed by 0.05 mg/kg bwt/h) IV. Concomitantly, 6 of the 13 jennies were sedated with dexmedetomidine 2.5 mcg/kg bwt followed by 2.5 mcg/kg bwt/h (Dex-B group), while seven jennies were sedated with xylazine 0.5 mg/kg bwt followed by 0.5 mg/kg bwt/h (Xyl-B group). A line block of the left flank and an infiltration block around uterine ligament were performed with lidocaine. While the jennies underwent ovariectomies standing, sedation scores and head height above ground were assessed at 2 and 10 min after sedative boluses and every 10 min thereafter. If sedation was too light or too deep, the dose of dexmedetomidine or xylazine was increased or decreased by 25% of the original infusion rate, while butorphanol infusion rate was constant. Physiological parameters were measured. Normally distributed data were compared using the two-sample t test while repeatedly measured data were tested for differences between and within groups using repeated measures analysis of variance (ANOVA) by ranks followed by a Wilcoxon test with Tukey Honest Significant Difference for multiple testing. Statistical significance was set at p < 0.05. RESULTS: Both Dex-B and Xyl-B caused moderate to marked sedation adequate for ovariectomy in donkeys. Evident sedation was absent by 60 min of termination of infusions. No adverse physiological effects were observed. MAIN LIMITATIONS: Study on ovariectomy cases only, no pharmacokinetic profiling. CONCLUSIONS: Dexmedetomidine or xylazine and butorphanol sedation is feasible for ovariectomy in standing donkeys.
Assuntos
Butorfanol , Dexmedetomidina , Equidae , Hipnóticos e Sedativos , Ovariectomia , Xilazina , Animais , Dexmedetomidina/administração & dosagem , Dexmedetomidina/farmacologia , Feminino , Butorfanol/administração & dosagem , Butorfanol/farmacologia , Ovariectomia/veterinária , Xilazina/farmacologia , Xilazina/administração & dosagem , Hipnóticos e Sedativos/administração & dosagem , Hipnóticos e Sedativos/farmacologia , Infusões Intravenosas/veterinária , Analgésicos Opioides/administração & dosagem , Analgésicos Opioides/farmacologiaRESUMO
BACKGROUND: Morphine is the prototypical µ-opioid receptor agonist used to provide analgesia in veterinary species. Its effects are well-described in horses but not donkeys. OBJECTIVES: To determine the antinociceptive effects of two doses of morphine in donkeys. To describe preliminary pharmacokinetic parameters of morphine in donkeys. STUDY DESIGN: In vivo experiment. METHODS: Eight adult castrated male donkeys were given intravenous (IV) 0.9% saline, morphine 0.1 mg/kg bwt (LDM), or morphine 0.5 mg/kg bwt (HDM) in a randomised order with a minimum 1-week washout period. Mechanical nociceptive thresholds (MNTs) were determined by a blinded investigator pre-injection and 15, 30, 45, 60, 90, 120, 150, 180, 210, 240, 300, and 360 min post-injection. Venous blood samples were collected pre-injection and 2, 5, 10, 15, 30, 45, 60, 90, and 120 min post-injection. Data were analysed using Friedman's test with Dunn's post hoc test for multiple comparisons. Pharmacokinetic parameters were calculated for the HDM treatment. RESULTS: Baseline MNT was [median (interquartile range)] 8.9 (7.1-10.3) N and did not differ between treatments. Peak MNTs occurred at 60 min for both LDM (16.2 N) and HDM (25.0 N) treatments. MNTs after HDM treatment were higher than saline (p < 0.04) at 15, 60, 90, 120, 150, 180, 240, and 300 min post-injection. MNTs after LDM treatment were higher than baseline (p < 0.05) at 45 and 60 min post-injection. Terminal half-life for HDM was (mean ± SD) 51.0 ± 10.7 min, the volume of distribution at steady-state 2.07 ± 0.33 L/min and clearance 49.2 ± 4.16 ml * min/kg using noncompartmental analysis. The concentration of morphine-3-glucuronide (M3G) was higher than morphine-6-glucuronide (M6G) at all sampled time points. MAIN LIMITATIONS: Short duration of plasma sampling for pharmacokinetic analysis; lack of objective measure of gastrointestinal function. CONCLUSIONS: The HDM treatment provided mechanical antinociception in donkeys with no significant adverse effects.