Anestesia epidural com lidocaína-metadona ou lidocaína-fentanil, em cadelas submetidas à ovário-histerectomia eletiva.

Abstract

The objective was to compare the anesthesia, analgesia and cardiopulmonary changes provided by methadone or fentanyl in combination with lidocaine, by epidural route in female dogs undergoing to elective ovariohysterectomy. It was used 18 female dogs distributed into two groups: LM - methadone (0.3 mg/kg) + 2% lidocaine without vasoconstrictor; and LF - fentanyl (5 ug/kg) + 2% lidocaine without vasoconstrictor. The drugs were administered by epidural route in a volume of 0.25 ml/kg. The female dogs were housed in experimental kennels for a period of seven days for adaptation to the site. The premedication consisted of acepromazine (0.1 mg/kg) and midazolam (0.3 mg/kg), both administered intramuscularly. Anesthesia was induced with propofol (4 mg/kg) in dose-effect system. It was registered: heart rate (HR) and respiratory (RR), rectal temperature (RT), systolic blood pressure (SBP) and blood glucose before and 15 minutes after premedication (T0 and T1); 15 minutes after the epidural (T2); five minutes after the dermotomia (T3); five minutes after the clamping of the ovarian pedicle (T4); five minutes, one, 3, 6, 12, 18 and 24 hours (T5, T6, T7, T8, T9, T10 and T11, respectively) after the end of the surgery. It were measured the number of reapplying of propofol and the total consumption, in mg/kg. We evaluated the analgesia by numerical descriptive scale. There was no significant difference in the SBP and HR between the groups, but hypotension occurred in some times in both groups. There was a significant reduction in the respiratory rate in the moment T6 in the LF group, significantly lower than in the Group LM. Hypothermia occurred in both groups, but there was a statistical difference compared to baseline, just in time T4 in the LF group. Blood glucose increased significantly only in the LF group, at times T4, T7 and T8. All animals of the LF group and eight of the LM group required propofol rebound in T4, but there was no significant difference in the number of reaplications and in the total consumption of propofol between the LF group (3 ± 1 reaplications, 7.5 ± 4.5 mg/kg) and LM (2 ± 2 reaplications, 4.5 ± 3.4 mg/kg). The period of latency and anesthetic and duration of surgical procedure were similar in both groups. Methadone provides more perioperative analgesia compared to fentanyl.