Synergistic Effects of Lidocaine and Fentanyl in Epidural Analgesia for Rabbits Undergoing Experimental Knee Surgery

Epidural analgesia is very effective for perioperative and postoperative pain control in animals undergoing surgery of the hind limb. This investigation intended to estimate the antinociceptive effect of Fentanyl and lidocaine in lumbosacral epidural analgesia in rabbits during stifle surgical operation. This study was performed on 18 adult male rabbits allocated into three groups. All rabbits were administered xylazine HCl (7.5 mg/kg) and ketamine HCl (35 mg/kg) via intramuscular injection. The rabbits were randomly assigned to three groups (n = 6); Group 1: epidural administration of 1 ml normal saline 0.9%; Group 2: epidural administration of lidocaine (4 mg/kg); Group 3: epidural administration of lidocaine (4 mg/kg) combined with fentanyl citrate (0.005 mg/kg). Comparisons were made among the groups. Compared to other groups, the analgesia was started after 46.15±1.8 seconds in group 3 earlier than in groups 1 and 2. Additionally, group 3 experienced flaccid paralysis for longer (38.5±1.5 min) than groups 1 and 2 (13.7±1.0 and 18.8±1.2 min). Furthermore, group 3 showed longer sensory blockades (42.15±1.3 min) than groups 1 and 2 (30.3±0.6 and 33.3±0.9 min). In conclusion, epidural lidocaine plus fentanyl induced a more potent antinociceptive effect, rapid onset of analgesia, and long duration of analgesia than lidocaine alone.