Comparison of ultrasound guided femoral and sciatic nerve block versus epidural anaesthesia for orthopaedic surgery in dogs

Objective: Comparison of ultrasound-guided femoral and sciatic nerve block versus epidural anaesthesia with bupivacaine and morphine for orthopaedic surgery of the pelvic limb in dogs with respect to analgesic effectiveness, clinical utility and side effects. Material and methods: The study included 22 dogs (American Society of Anesthesiologists, ASA grades I and II) undergoing orthopaedic surgery distal to the mid-femoral bone. The study was designed as a randomized, prospective, blinded clinical trial. All dogs were randomly assigned to receive 0.5 mg/kg bupivacaine (0.5%) and 0.1 mg/kg morphine sulphate (1%) either as epidural anaesthesia (group EPI) or by ultrasound-guided femoral and sciatic nerve block (group LA). During surgery, the heart rate, respiratory rate, mean arterial pressure (MAP), end -tidal isoflurane concentrations and dose of rescue analgesia (fentanyl boluses of 5 mu g/kg i. v.) were measured. Pain severity was scored (short form of the Glasgow Composite Measure Pain Scale, GCMPS) before surgery and postoperatively at 2, 4, 6, 12 and 24 hours after extubation. Post-operative rescue analgesia consisted of methadone (0.2 mg/kg i. v.), and was applied when the GCMPS > 6. For statistical analysis, the Chi-square, Fisher, and Wilcoxon tests and one and two-way ANOVA were applied. Differences were considered statistically significant at p < 0.05. Results: Only the MAP was significantly different between the two treatment groups. Intra- and postoperative MAP of group LA (111.2 +/- 11.2 mmHg and 119.3 +/- 18.2 mmHg, respectively) was higher than in group EPI (86.6 +/- 8.7 mmHg and 95.2 +/- 13.1 mmHg, respectively). None of the dogs developed urinary retention or ambulatory deficits when completely recovered from anaesthesia. No other side effects were noted. Clinical relevance: In conclusion, femoral and sciatic nerve blocks and epidural anaesthesia ensure comparable analgesic effects in canine patients undergoing orthopaedic surgery of the pelvic limb. The lower mean arterial blood pressure of group EPI was not of clinical relevance.