Comparison of Perioperative Analgesic Protocols and Evaluation of the Development of a Chronic Neuropathic Pain State in Dogs Undergoing TPLO for Naturally Occurring Cranial Cruciate Ligament Rupture

Introduction: Neuropathic pain is a complex, chronic pain state caused by malfunction of the somatosensory nervous system and is manifested as reduced sensory threshold (ST). Our aim was to assess the effect of three perioperative analgesic protocols ST in dogs with cruciate ruptures: perioperative opioid administration alone, epidural analgesia, and direct femoral, and sciatic nerve blockade. We hypothesized that while perioperative opioids alone would provide equivalent immediate postoperative analgesia when compared with the two other treatments, that ST at later time points would be lower in dogs receiving only opioid administration.

Materials and Methods: Client owned dogs with cruciate rupture were enrolled. Dogs were randomly assigned to receive; Treatment 1- perioperative intravenous morphine, lidocaine, and ketamine; Treatment 2 - epidural; Treatment 3 - a femoral and sciatic nerve blockade. Routine stifle arthroscopy followed by TPLO surgery was performed. Temporospatial gait analysis and ST data were collected before surgery, 1 day, 2 and 8 weeks postoperatively. Sedation and pain scores were assessed at 0, 4, 8, and 24 hours following extubation.

Results: No significant differences were seen in ST or gait analysis between groups at any time point. Sedation scores for Treatment 1 were higher than other treatments. Pain scores were lower for Treatment 3 than other treatments.

Discussion/Conclusion: Perioperative analgesic protocol does not appear to significantly impact long-term ST in dogs with spontaneous CR. Although all treatments appeared to provide adequate analgesia, femoral-sciatic blockade presented the best combination of analgesia with least sedation.

Acknowledgment: None.