Comparison of epidural buprenorphine and morphine for post-operative analgesia in dogs

Abstract

Buprenorphine is an effective analgesic when administered epidurally to humans. The purpose of this study was to compare epidural buprenorphine (B; n = 10) with epidural morphine (M; n = 10) for post-operative analgesia in dogs undergoing cranial cruciate ligament repair. All dogs were premedicated with acepromazine (0.1 mg kg−1 IM), induced with propofol (4–6 mg kg−1 IV) and maintained with halothane in oxygen. Dogs were randomly assigned to receive B (0.004 mg kg−1) or M (0.1 mg kg−1) in the lumbosacral epidural space in a total volume of 0.2 mL kg−1. End-tidal halothane and CO2 and temperature were recorded every 15 minutes until extubation (t = 0). A numerical rating pain score (SPS) was recorded at t = 0, 1, 2, 4, 6, 10 and 24 hours by a blinded observer. Dogs received rescue morphine (1.0 mg kg−1 IM) if indicated by SPS and the time of rescue analgesic administration was recorded. Observable side-effects such as urinary retention, sedation or pruritus were recorded. Data were analyzed with repeated measures anova. Mean ± SD body weight (kg) and age (yrs) for B dogs was 34.2 ± 10.8 and 5.5 ± 2.8; for M dogs these values were 36.6 ± 13.5 and 5.9 ± 3.3. Mean ± SD SPS for B dogs at t = 0, 1, 2, 4, 6, 10 and 24 hours were 1.2 ± 0.75, 3.2 ± 2.0, 4.5 ± 4.3, 4.6 ± 3.4, 4.7 ± 3.0, 5.0 ± 4.9 and 5.1 ± 3.5. For M dogs these values were 1.7 ± 0.5, 2.6 ± 2.0, 3.7 ± 0.75, 4.2 ± 2.2, 4.1 ± 3.0, 3.1 ± 2.1 and 3.9 ± 1.9. There were no significant differences between B and M with respect to SPS, times or frequency of rescue morphine administration, end-tidal halothane and CO2, or esophageal temperature. Fifty per cent of dogs in both groups required rescue morphine. Buprenorphine is as effective as morphine for epidural analgesia in healthy dogs undergoing hindlimb orthopedic surgery.