Purpose: To compare the postoperative analgesic effects of the extradural tramadol or morphine in female dogs undergoing ovariohysterectomy.
Methods: Sixteen female dogs were randomly assigned to two groups of eight animals each and received morphine (0.1 mg kg(-1) M group) or tramadol (2 mg kg(-1) T group). The pre-anesthetic medication was intravenously (iv) acepromazine (0.05 mg kg(-1)). Anesthesia was induced with propofol (4 mg kg(-1)iv) and maintained with isoflurane. The degree of analgesia was evaluated using a numerical rating scale that included physiologic and behavior variables. Dogs were scored at one, three, six and 12 hours after surgery by one blinded observer. Dogs were treated with morphine (0.5 mg kg(-1)) if their scores were >6. Serum cortisol was measured before the pre-anesthetic medication was administered (basal), at the time of the ovarian pedicle clamping (T0), and at 1 (T1), 6 (T6) and 12 (T12) hours postoperative.
Results: The pain score did not differ between morphine and tramadol treatments. Rescue analgesia was administered to one dog in the T treatment group. Serum cortisol did not differ between treatments.
Conclusion: The extradural administration of morphine or tramadol is a safe and effective method of inducing analgesia in female dogs undergoing ovariohyterectomy.