Effects of detomidine or romifidine during maintenance and recovery from isoflurane anaesthesia in horses

Abstract

Objective: To evaluate the effects of detomidine or romifidine on cardiovascular function, isoflurane requirements and recovery quality in horses undergoing isoflurane anaesthesia.

Study design: Prospective, randomized, blinded, clinical study.

Animals: A total of 63 healthy horses undergoing elective surgery during general anaesthesia.

Methods: Horses were randomly allocated to three groups of 21 animals each. In group R, horses were given romifidine intravenously (IV) for premedication (80 μg kg^-1), maintenance (40 μg kg^-1 hour^-1) and before recovery (20 μg kg^-1). In group D2.5, horses were given detomidine IV for premedication (15 μg kg^-1), maintenance (5 μg kg^-1 hour^-1) and before recovery (2.5 μg kg^-1). In group D5, horses were given the same doses of detomidine IV for premedication and maintenance but 5 μg kg^-1 prior to recovery. Premedication was combined with morphine IV (0.1 mg kg^-1) in all groups. Cardiovascular and blood gas variables, expired fraction of isoflurane (Fe'Iso), dobutamine or ketamine requirements, recovery times, recovery events scores (from sternal to standing position) and visual analogue scale (VAS) were compared between groups using either anova followed by Tukey, Kruskal-Wallis followed by Bonferroni or chi-square tests, as appropriate (p < 0.05).

Results: No significant differences were observed between groups for Fe'Iso, dobutamine or ketamine requirements and recovery times. Cardiovascular and blood gas measurements remained within physiological ranges for all groups. Group D5 horses had significantly worse scores for balance and coordination (p = 0.002), overall impression (p = 0.021) and final score (p = 0.008) than group R horses and significantly worse mean scores for VAS than the other groups (p = 0.002).

Conclusions and clinical relevance: Detomidine or romifidine constant rate infusion provided similar conditions for maintenance of anaesthesia. Higher doses of detomidine at the end of anaesthesia might decrease the recovery quality.

Keywords: anaesthesia; detomidine; horse; recovery; romifidine; sedation.