Perineal analgesia and hemodynamic effects of the epidural administration of meperidine or hyperbaric bupivacaine in conscious horses.

Epidural administration of bupivacaine and meperidine produces analgesia in several animal species and in humans. A prospective randomized study was conducted in 18 healthy horses to compare the effect of these 2 drugs administered by the epidural route. Animals were divided into 3 treatment groups of 6 animals each. All drugs were injected by the epidural route in all animals between the 1st and 2nd coccygeal vertebrae. Treatment 1 (BUP)--0.06 mg/kg of body weight of 0.5% hyperbaric bupivacaine; treatment 2 (MEP)--0.6 mg/kg of body weight of 5% meperidine; treatment 3 (SS)--0.9% saline solution (control group). Heart rate, arterial pressure, respiratory rate, rectal temperature, analgesia, sedation, and motor-blocking were determined before drug administration (baseline values); at 5, 10, 15, and 30 minutes after drug administration, and then at 30-minute intervals thereafter. Both hyperbaric bupivacaine and meperidine administered epidurally produced complete bilateral perineal analgesia in all horses. The onset of analgesia was 6, s = 2.6 minutes after injection of bupivacaine, as opposed to 9, s = 2 minutes after meperidine. The duration of analgesia was 240, s = 57 minutes for meperidine and 320, s = 30 minutes for bupivacaine. Heart and respiratory rates, arterial pressure, and rectal temperature did not change (P < 0.05) significantly from basal values after the epidural administration of bupivacaine, meperidine, or saline solution. To conclude, both bupivacaine and meperidine induced long-lasting perineal analgesia, with minimal cardiovascular effects. Analgesia was induced faster and lasted longer with bupivacaine.

Perineal analgesic actions of epidural clonidine in cattle.

OBJECTIVE: To determine the analgesic, sedative, motor, cardiac and respiratory effects of epidural clonidine in cattle. STUDY DESIGN: Prospective randomized study. ANIMAL POPULATION: Six healthy male cattle weighing between 236 and 365 kg. METHODS: To investigate the effect of epidural clonidine, the animals received 2 and 3 micro g kg(-1) of clonidine diluted to 8 mL with 0.9% saline. Two treatments were utilized as controls. The animals from the first control treatment received 2% lidocaine (0.4 mg kg(-1)) and those from the second received an equal volume of 0.9% saline. Each animal received each treatment in random order. Evaluations of analgesia, sedation, muscle relaxation, heart rate, respiratory rate and rectal temperature were obtained at 0 (basal), 2, 5, 10, 15 and 30 minutes after epidural injection, and then at 30-minute intervals until loss of analgesia occurred. All the animals received a standard noxious stimulus consisting of needle insertion into the skin and deep muscle; a 4-point scale was used to score the response. A second scale was used to score sedation and a third for muscle relaxation. RESULTS: Both doses of clonidine were effective in producing analgesia of the tail, perineum, and upper hindlimb. Complete analgesia was present before (mean +/- SE = 9 +/- 4 vs. 19 +/- 9 minutes) and lasted longer (311 +/- 33 vs. 192 +/- 27 minutes) for the 3 microg kg(-1) versus the 2 microg kg(-1) dose, respectively. A dose-dependent sedative effect of clonidine was also observed, with a peak effect between 60 and 180 minutes. No effects on heart or respiratory rates were observed with either dose of clonidine. CONCLUSIONS: Epidural administration of 2 and 3 micro g kg(-1) of clonidine in cattle in this study provided bilateral perineal analgesia/anesthesia with a dose-dependent onset and duration of action. CLINICAL RELEVANCE: Further studies are required to determine whether the analgesia is sufficient for surgery.