Sedative and cardiovascular effects of premedication with acepromazine, methadone and dexmedetomidine in sevoflurane-anaesthetized dogs.

OBJECTIVE

To evaluate the sedative and cardiovascular effects of premedication with acepromazine, methadone and dexmedetomidine or acepromazine and methadone in sevoflurane-anaesthetized dogs.

STUDY

DESIGN

A randomized, blinded, prospective clinical study.

ANIMALS: A total of 38 client-owned healthy dogs scheduled for elective surgery.

METHODS

Dogs were randomly assigned to intramuscular premedication with acepromazine (0.01 mg kg-1), methadone (0.3 mg kg-1) and dexmedetomidine (1.5 μg kg-1) (Ace/D group) or with acepromazine (0.01 mg kg-1) and methadone (0.3 mg kg-1) (Ace group). The anaesthetist who performed the observations and anaesthesia was blinded to the group. Sedation was scored at 5, 10 and 15 minutes after premedication and postoperatively every hour until discharge, starting 30 minutes after extubation. Anaesthesia was induced with propofol and maintained with sevoflurane in oxygen and air. Body temperature, heart rate (HR), respiratory rate (fR), direct arterial blood pressure, end-tidal sevoflurane, end-tidal carbon dioxide (Pe´CO2) and oxygen saturation were recorded at 5 minute intervals. The normality of data distribution was assessed with the Shapiro-Wilk test. The Mann-Whitney U test was used for comparison between groups, and effect size was calculated in cases of statistical significance (p < 0.05).

RESULTS

Dogs in the Ace/D group had significantly higher sedation scores 10 minutes after premedication (p = 0.02). The propofol induction doses were significantly lower in the Ace/D group (p = 0.001). During anaesthesia, dogs in the Ace/D group had significantly higher Pe´CO2 values (p = 0.03), but no significant differences in blood pressure, HR and fR were observed between the groups. Significantly fewer dogs in the Ace/D group required rescue analgesia with fentanyl (p = 0.04) during surgery (three in Ace/D and nine in Ace group).

CONCLUSIONS

Low-dose dexmedetomidine improved preoperative sedation and intraoperative analgesia and reduced the induction dose of propofol in dogs premedicated with acepromazine and methadone.