Comparison of the effects of methadone and butorphanol combined with acepromazine for canine gastroduodenoscopy

Abstract

Objective: To evaluate the feasibility of gastroduodenoscopy in dogs premedicated with acepromazine in combination with butorphanol or methadone.

Study design: Prospective, randomized, double-blinded clinical trial.

Animals: A group of 40 client-owned dogs.

Methods: Dogs were randomly allocated to one of two groups and give intramuscular acepromazine 0.02 mg kg^-1 combined with either butorphanol 0.3 mg kg^-1 (group ACEBUT) or methadone 0.2 mg kg^-1 (group ACEMET). General anaesthesia was induced with propofol and ketamine and maintained with sevoflurane (2.3%) in oxygen. Cardiopulmonary variables were recorded at 5 minute intervals during anaesthesia. Feasibility of the entire gastroduodenoscopy was evaluated with a visual analogue scale (VAS) from 0 (best) to 100 (worst) (primary outcome of the study). Lower oesophageal sphincter dilatation and duodenal intubation were scored. Pylorus diameter was measured with standard endoscopic inflatable balloons. Overall cardiovascular stability was assessed during anaesthesia, using a VAS (0-100), as was the presence of fluid in the oesophagus, regurgitation, need for mechanical ventilation, and intraoperative and postoperative rescue analgesia (secondary outcomes of the study). Differences between treatments were analysed with Mann-Whitney U, Student t test, Fisher exact test or mixed model analysis of variance as appropriate. Subsequently, feasibility VAS of the gastroduodenoscopy was assessed for noninferiority between groups. The noninferiority margin was set as -10.

Results: All gastroduodenoscopies were successfully completed in both groups using an endoscope tip diameter of 12.8 mm in all but one dog. Feasibility of gastroduodenoscopy was evaluated as 2.9 ± 5.6 in group ACEBUT and 5.1 ± 5.8 in group ACEMET. No significant differences between groups were detected in any measured or assessed variables, and noninferiority was confirmed.

Conclusion and clinical relevance: In our study population, the effects of methadone and butorphanol when combined with acepromazine were comparable.

Keywords: acepromazine; butorphanol; dog; gastroduodenoscopy; methadone.