Dexmedetomidine and Bupivacaine Association in Caudal Epidural Injection in Mares

Abstract The objective of the study was to compare the effects of caudal epidural bupivacaine and dexmedetomidine (DEX) combination, with bupivacaine or DEX plain for perineal analgesia in mares. Six healthy saddle mares weighing 330-370 kg and aged 10-15 years were used in this study. Each mare was assigned to receive three treatments: 0.04 mg/kg 0.25% bupivacaine (BP), 2 μg/kg dexmedetomidine (DX) or 0.02 mg/kg bupivacaine and 1 μg/kg dexmedetomidine (BPDX). The order of treatments was randomised. All drugs were injected into the caudal epidural space (Co1-Co2) through a 16-G Tuohy epidural needle. After the epidural injections, heart rate, respiratory rate, arterial blood pressures (systolic, diastolic and mean) and rectal temperature were measured at 5, 10, 15, 30, 60, 90 and 120 minutes, and after this time every 60 minutes until the end of the experiments. A subjective score system was used to assess analgesia, behavioural and motor blockade at the same time points. The BPDX treatment produced analgesic action with twice the duration (200 minutes) of the BP treatment (97 minutes), but with an analgesic duration shorter than the DX treatment (240 minutes) in the regions of the tail, perineum and upper hind limbs in mares. All treatments showed mild motor blockade. No behavioural changes were observed in any of the animals. There was hemodynamic stability without significant changes in respiratory rate for all treatments. Epidural analgesia using dexmedetomidine alone or the combination of dexmedetomidine and bupivacaine may be an option for painful obstetric and gynaecological procedures in mares.