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

Abstract

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)

Influence of Epinephrine and Medetomidine on Systemic Absorption of Lidocaine Applied Epidurally in Anesthetized Swine

“…In previous studies epinephrine has been shown, not only to decrease local anesthetic systemic absorption rate, but also to prolong duration and improve quality of the epidural block when applied in combination with the moderately potent lidocaine, as well as with more dilute solutions of potent local anesthetics like bupivacaine or ropivacaine [11,16,19,20]. On the contrary, the most likely reason why the same results were not recorded when epinephrine was added to concentrated solutions of bupivacaine and ropivacaine is that duration of action of these agents exceeds the duration of epinephrine's effects [16].…”

Use and Efficacy of Analgesic Agents in Sheep (Ovis aries) Used in Biomedical Research

“…45,67 These studies recorded time to voluntary leg withdrawal from the stimulus. Other studies utilized superficial or deep muscle pinpric ks, 3,[11][12][13][14]17,21,22,26,39,42,59 as an alternative method of mechanical stimulation of so-called 'first-pain.' 9 This method tends to evaluate analgesia by using a scale based on reaction to the stimulus.…”

“…68 Butorphanol, a κ agonist and partial μ agonist, was used in only one reviewed study. 17 Sheep given butorphanol intramuscularly required a 28% increase in isoflurane minimum alveolar concentration for maintenance of anesthetic depth, compared with sheep that received epidural morphine and bupivacaine. In addition, sheep given butorphanol had higher heart rates and an increased rate of bloating after recovery.…”

“…35,38 Two studies support this finding in sheep and further suggest that morphine alone provides unsatisfactory analgesia. 12,17 This combination provided an extended duration of analgesia compared with that of either bupivacaine or morphine alone. In addition, the demand for inhalant anesthetic was reduced relative to morphine alone.…”

“…In addition, the demand for inhalant anesthetic was reduced relative to morphine alone. 17 However, prolonged sympathetic motor blockade may result due to the local anesthetic. When motor blockade extends into the cervical region, it can affect diaphragmatic function, through alteration of phrenic nerve stimulation.…”