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.