Comparison of detomidine and romifidine as premedicants before ketamine and halothane anesthesia in horses undergoing elective surgery

Objective-To compare detomidine hydrochloride and romifidine as premedicant s in horses undergoing elective surgery. Animals-100 client-owned horses. Procedure-After administration of acepromazine (0.03 mg/kg, IV), 50 horses received detomidine hydrochloride (0.02 mg/kg of body weight, IV) and 50 re ceived romifidine (0.1 mg/kg, IV) before induction and maintenance of anest hesia with ketamine hydrochloride (2 mg/kg) and halothane, respectively. Ar terial blood pressure and blood gases, EGG, and heart and respiratory rates were recorded. Induction and recovery were timed and graded. Results-Mean (+/- SD) duration of anesthesia for all horses was 104 +/- 28 minutes. Significant differences in induction and recovery times or grades were not detected between groups. Mean arterial blood pressure (MABP) decre ased in both groups 30 minutes after induction, compared with values at 10 minutes. From 40 to 70 minutes after induction, MABP was significantly high er in detomidine-treated horses, compared with romifidine-treated horses, a lthough more romifidine-treated horses received dobutamine infusions. In al l horses, mean respiratory rate ranged from 9 to 11 breaths/min, Pao(2) fro m 200 to 300 mm Hg, Paco(2) from 59 to 67 mm Hg, arterial pH from 7.33 to 7 .29, and heart rate from 30 to 33 beats/min, with no significant difference s between groups. Conclusions and Clinical Relevance-Detomidine and romifidine were both sati sfactory premedicants. Romifidine led to more severe hypotension than detom idine, despite administration of dobutamine to more romifidine-treated hors es. Both detomidine and romifidine are acceptable alpha (2)-adrenoceptor ag onists for use as premedicants before general anesthesia in horses; however , detomidine may be preferable when maintenance of blood pressure is partic ularly important.