Evaluation of nalbuphine, butorphanol and morphine in dogs during ovariohysterectomy and on early postoperative pain

Abstract

Objective: To evaluate the effects of nalbuphine, butorphanol and morphine combined with acepromazine on intraoperative and early postoperative pain management in dogs anesthetized for ovariohysterectomy.

Study design: Prospective, randomized blinded clinical study.

Animals: A total of 48 healthy female dogs of different breeds, aged 1-6 years, weighing (mean ± standard deviation) 14.5 ± 4.8 kg.

Methods: Dogs were randomly assigned into four groups to be intravenously administered nalbuphine (0.5 mg kg^-1; group N0.5), nalbuphine (1.0 mg kg^-1; group N1.0), butorphanol (0.4 mg kg^-1; group B0.4) or morphine (0.2 mg kg^-1; group M0.2) combined with acepromazine (0.02 mg kg^-1) prior to propofol and isoflurane for anesthesia. Heart rate (HR), respiratory rate, systolic arterial pressure and rectal temperature (RT) were recorded at time points during anesthesia. A dynamic interactive visual analog scale applied in three phases (DIVAS I, II and III) and the modified Glasgow composite measure pain scale were used to assess pain before premedication and 1, 2, 3, 4, 5 and 6 hours after extubation. Administration of rescue analgesia was recorded.

Results: At the left ovarian pedicle ligation, HR was higher in N1.0 than in B0.4 (p = 0.020). RT decreased significantly by the end of surgery in N0.5 (p = 0.043) and B0.4 (p = 0.010). Rescue analgesia was administered postoperatively over 6 hours to eight, seven, nine and 10 dogs in N0.5, N1.0, B0.4 and M0.2, respectively (p = 0.57). DIVAS II was higher in B0.4 than in N1.0 at 2 and 3 hours (p = 0.038 and p = 0.002, respectively) and N0.5 at 3 hours (p = 0.003).

Conclusions and clinical relevance: At the doses used, all premedication protocols provided insufficient intraoperative analgesia, with minimal clinical differences between groups. No premedication provided satisfactory analgesia in the first 6 hours postoperatively.

Keywords: agonist-antagonist; analgesia; dog; opioid; pain scale.