Preoperative epidural administration of morphine or methadone for analgesia in female dogs undergoing to ovariohysterectomy*

Abstract

The analgesia and cardiopulmonary changes provided by methadone or morphine, by epidural route, were compared in female dogs undergoing to ovariohysterectomy. Sixteen female dogs were distributed into two groups, which received 0.3 mg/kg of methadone (MET group) or 0.1 mg/kg of morphine (MORPH group), both by lumbosacral epidural route. The anesthesia was maintained with isoflurane. Heart and respiratory rates, body temperature, systolic, mean and diastolic arterial pressure, cortisol and analgesia were evaluated. The analgesia was measured by numerical descriptive scale which has as a maximum score 25 points. In case a score superior to 16 was detected, morphine was administered (0.5 mg/kg, IM). The following moments were considered: before and 15 minutes after the pre-anesthetic medication (M0 e M1); 15, 50, 55, 65 and 95 minutes after the epidural puncture (M2, M3, M4, M5 and M6, respectively); 2, 4, 7, 13, 19 and 25 hours (M7, M8, M9, M10, M11 and M12, respectively) after the epidural puncture. The cortisol was measured before the measurement of the physiological parameters, in the moments M0, M3, M4, M8, M10 and M12. A reduction in the respiratory rate and decrease of body temperature occurred in both groups. Cortisol increased in the MORPH group at the clamping of the ovarian pedicles (6.10 ± 1.85 μg/dL) and in the MET group, four hours after the epidural puncture (9.05 ± 7.77 mg/dL), but none of the animals needed rescue analgesia and the analgesia was intense in both groups. Morphine and methadone have similar analgesic efficacy, and do not cause significant cardiopulmonary changes.