Effect of bupivacaine on epidural analgesia produced by xylazine or medetomidine in buffaloes (Bubalus bubalis).

Objective: To evaluate and compare the effect of epidural bupivacaine on analgesia produced by epidural xylazine or medetomidine in buffaloes.

Study Design: Prospective, blinded study.

Animals: Ten male buffalo calves (6-8 months of age; body weight 70-90 kg) were used on two occasions to conduct a total of 20 investigations.

Methods: Caudal extradural analgesia was produced in four buffalo calves each by the injection of either xylazine (0.05 mg kg(-1)), medetomidine (15 microg kg(-1)) or 0.5% bupivacaine (0.125 mg kg(-1)), or combinations of xylazine and bupivacaine (0.05 and 0.125 mg kg(-1)), or medetomidine and bupivacaine (15 microg kg(-1) and 0.125 mg kg(-1)) at the first intercoccygeal extradural space. Analgesia was tested using deep pinprick stimuli.

Results: Extradural administration of xylazine or medetomidine resulted in complete analgesia of the tail, perineum, inguinal region and the upper parts of the hind limbs, which was faster in onset and longer in duration in the medetomidine group than in the xylazine group. Addition of bupivacaine increased the intensity of the analgesia produced by xylazine, but not that produced by medetomidine. All the drugs caused mild to moderate ataxia, but signs of sedation were apparent only in animals which received xylazine or medetomidine. The extradural injections of all the drugs caused significant decrease in heart rate (p = 0.024), respiratory rate (p = 0.026) and rectal temperature (p = 0.036) from the respective baseline values, but the differences between the groups were not significant.

Conclusions: Medetomidine produced a longer duration of analgesia than that produced by xylazine. Bupivacaine prolonged the analgesia produced by xylazine, but the analgesia produced by the combination of medetomidine and bupivacaine was not superior to that produced by medetomidine alone.

Clinical Relevance: Bupivacaine may be used to prolong the extradural analgesia produced by xylazine, but not that produced by medetomidine in buffaloes.