TRANS AND POSTOPERATIVE ANALGESIA OF EPIDURAL MORPHINE OR FENTANYL IN DOGS SUBMITTED TO ATLANTO-AXIAL BIOPSY.

Abstract

The aim of the study was to evaluate analgesia and cardiorespiratory alterations produced by morphine or fentanil epidural during atlanto-axial biopsy, besides the postoperative analgesic quality promoted by those drugs. In a blind study, 16 mixed healthy dogs were used. After preanesthetic medication with 0,1mg/kg of acepromazine IV, they received 0,1mg/kg of morphine (GM) or 4µg/kg of fentanil (GF) epidural with lidocaine, resulting in 0,25ml/kg final volume. Anesthesia was obtained with 4mg/kg of propofol following halothane. HR, SAP, MAP, DAP, f, SpO₂ and TºC were measured. Halothane vaporization was adapted according to MAP, maintaining it between 70 and 90mmHg.  Postoperative evaluations were done at 3, 4, 6, 8, 12 and 24 hours post-epidural. There was reduction of halothane vaporization in both groups. SAP and MAP decreased considerably 20 min post-epidural in both groups. Apnea was observed in five animals of GF and two animals of GM, which were maintained under artificial ventilation. The groups did not differ themselves on postoperative evaluation. However, two animals of GF needed supplementary analgesia, suggesting inferiority as postoperative analgesic. It was concluded that two opioids reduced halothane demand significantly, evidencing trans-operative analgesic effect. However, fentanil promoted marked breathing depression in that period. Besides, it could be suggest a reduced postoperative analgesia of fentanil compared to morphine, mainly due the necessity of supplementary doses on postoperative period.

KEY-WORDS: Morphine. Fentanyl. Epidural. Dogs.