Efficacy of epidural administration of morphine with bupivacaine for orthopaedic surgery in sheep

The aim of the study was to test the hypothesis that epidural administration of morphine with bupivacaine provides more intense and sufficient perioperative analgesia compared with parenterally administrated butorphanol during orthopaedic surgery. Sheep were assigned to group C (control group, 6 sheep) and group E (epidural, 5 sheep). Sheep from group C were pre-medicated with midazolam (0.3 mg/kg, i.m.) and butorphanol (0.2 mg/kg, i.m.). Propofol was used for induction of general anesthesia in both groups. Sheep from group E were pre-medicated with midazolam, but without butorphanol. Sacrococcegeal epidural analgesia with morphine (0.1 mg/kg) and bupivacaine (1 mg/kg) was performed. We detected a significant increase in heart rate (19%, p=0.021) during surgery in group C. Two hours after surgery, the heart rate was 14.9% lower than prior to surgery in group E (p=0.017). In group E, throughout the surgery, we measured an insignificant increase in respiratory rate of 1.99%. In the same group, 120 minutes post surgery, we measured an increase in respiratory rate of 14.7%, while in group C there was a smaller increase of only 10.9%. The result from both groups was insignificant (p>0.05). The consumption of isoflurane in group C was higher than in group E by 27.3% (p=0.0043). The mean MAC was in group C higher by 27.6% as it was in group E (0.75% ± 0.25, 0.95 ± 0.3 in Group E and C, respectively). This distinction, according to the Mann-Whitney test, was not significant (p=0.329)