Analgesia peridural com ropivacaína associada ao midazolam em cadelas submetidas à ovariosalpingohisterectomia

This research aimed evaluate the parametric, analgesic, sedative effects and most appropriate dose of midazolam (50 or 100μg.kg-1) for epidural anesthesia in bitches submitted an elective ovariosalpingohisterectomy. Twenty-four bitches tool part study, adults, different breeds, mediun weigh 8.25 ± 2.26 kg and premedicated with acepromazine (0.05 mg.kg-1, IM), followed by anesthetic induction and maintenance with propofol (5mg.kg-1) and isoflurane, respectively, and allocated in three experimental groups: GR - ropivacaine 0.2 mL.kg-1, GM50 - midazolam (50μg.kg-1) + ropivacaine 0.2 mL.kg-1 and GM100 - midazolam (100μg.kg-1) + ropivacaine 0.2 m.Lkg-1. The heart and respiratory rate, indirect systolic arterial pressure, rectal temperature, oxygen saturation in hemoglobin, blood gas variables, plasma cortisol, degree of postoperative analgesia and sedation were evaluated. The results was submitted to ANOVA followed by Tukey test in the SAS (p <0.05). From the qualitative variables were performed ordinal tests Kruskal-Wallis, Friedman and Dunn tests. Were observed effects more durable local anesthetic in the group of animals that used the 100μg/kg dose of midazolam as compared to the groups GM50 e GR. Additionally, 50% of the animals tested GM100 received rescue analgesia 12 hours after surgery. The combination of midazolam in the dose of ropivacaine had 100μg/kg the upper end of the dose of midazolam 50μg.kg-1, not increasing the analgesic effect, however, extending the period of residual postoperative analgesia. It was concluded that the association of midazolam to ropivacaine did not produce significant parametric changes or additional sedation effects, but midazolam in 100μg.kg-1 may be another option in releave post-operative pain in bitches subjected the OSH.