The Antinociceptive Effects of Epidural Tramadol with Bupivacaine in Beagle Dogs

This study investigated the antinociceptive effect of epidural tramadol with bupivacaine in 36 healthy Beagle dogs. The dogs were divided into 6 groups; 1) C (control), 2) B (0.5% bupivacaine 0.1 mL/kg), 3) BT0.5 (0.5% bupivacaine 0.1 mL/kg + tramadol 0.5 mg/kg), 4) BT1 (0.5% bupivacaine 0.1 mL/kg + tramadol 1 mg/kg), 5) BT2 (0.5% bupivacaine 0.1 mL/kg + tramadol 2 mg/kg), 6) BT3 (0.5% bupivacaine 0.1 mL/kg + tramadol 3 mg/kg). The epidural injection was performed under isoflurane inhalation, after then, nociceptive block and motor block scores were assessed with physiologic parameters (HR, RR, RT, MAP). BT groups showed significantly longer antinociceptive time than C and B, while motor block time of BT groups were not different from B except BT3. Durations of total nociceptive block of BT2 ($60.83{\pm}19.08min$) and BT3 ($74.17{\pm}8.61min$) were significantly longer than those of BT0.5 ($33.33{\pm}8.76min$) and BT1 ($37.50{\pm}19.43min$), but there was no significant difference between BT2 and BT3. Durations of total motor block in all groups were less than 20 minutes although that of BT3 was significantly longer than B. There were no significant differences in HR, RR, RT, MAP among groups. Consequently, epidural administration of tramadol (2 mg/kg) with 0.5% bupivacaine (0.1 mL/kg) can be used safely and effectively in dogs.