In this study, the analgesia effects of intravenous injection either of lidocaine, fentanyl, or their combination were compared in dogs undergoing ovariohysterectomy. Forty-eight dogs were randomly assigned into three groups. Anesthesia was induced with 6 mg/kg propofol and maintained with 2% (vaporizer dial setting) isoflurane. Animals received lidocaine (4 mg/kg), fentanyl (3 μg/kg), and their combination after 15 minutes of induction. Heart rhythm, respiratory rhythm, blood pressure, rectal temperature, subjective pain scores and arterial blood-gas were measured at same time. Cardiopulmonary variables changed after injection, and some of them had significant differences compared with baselines at the moment of extubation. The maximal subjective pain scores were recorded at three hours after extubation, but rescue analgesic was not required at this study. Though values regarding blood gas changed after intravenous administration of agents, significant differences were not found between groups at any of the time-points. Both drugs and their combination provided adequate analgesia undergoing ovariohysterectomy in dogs. No side effects were observed, no rescue analgesic was required.

Key words: Canine, Fentanyl, Lidocaine, Ovariohysterectomy, Physiological parameters