Effect of epidural dexmedetomidine with or without local anesthetics on pain score and serum IL-6 levels in dogs undergoing elective ovariohysterectomy

Abstract

To evaluate the postoperative analgesic effects of epidural dexmedetomidine with or without local anesthetics, prospectiverandomized double-blinded clinical trials were performed with 24 healthy client-owned mixed-breed adult dogs with an average weightof 18.1 ± 2.4 kg allotted equally (n = 6) to four groups: A, B, C, and D. All animals were premedicated intramuscularly with atropine(0.04 mg/kg) and after 5 min by intravenous midazolam (0.7 mg/kg). After 10 min of premedication, in group A dexmedetomidine(7 μg/kg) and in groups B, C, and D, in addition to dexmedetomidine (7 μg/kg), lidocaine (4.4 mg/kg), bupivacaine (2 mg/kg), andropivacaine (2 mg/kg), respectively, were administered to the lumbosacral epidural space, respectively. Anesthesia was maintainedwith 1% propofol as and when needed. Postoperative analgesia was assessed subjectively using the University of Melbourne Pain Scale(UMPS) at 1, 2, 4, and 24 h postoperatively and objectively by measuring the circulating levels of interleukin-6 (IL-6) at 0 (baseline),1, 2, 4, and 24 h postoperatively. Overall, UMPS scores were lower in groups B, C, and D at all time points compared to group A.Serum IL-6 levels showed a nonsignificant decrease in groups B and C with a nonsignificant increase in group D at different intervalsas compared to baseline. However, a significantly higher serum IL-6 level was recorded at 4 h in group A as compared to the otherthree groups. It was concluded that epidural dexmedetomidine in combination with lidocaine, bupivacaine, or ropivacaine at the dosesstudied provides better postoperative analgesia than dexmedetomidine alone in dogs undergoing elective ovariohysterectomy. However,the dexmedetomidine/ropivacaine combination revealed comparatively lower postoperative analgesia than dexmedetomidine/lidocaineand dexmedetomidine/bupivacaine combinations.