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

To compare detomidine hydrochloride and romifidine as premedicants in horses undergoing elective surgery.

100 client-owned horses.

After administration of acepromazine (0.03 mg/kg, IV), 50 horses received detomidine hydrochloride (0.02 mg/kg of body weight, IV) and 50 received romifidine (0.1 mg/kg, IV) before induction and maintenance of anesthesia with ketamine hydrochloride (2 mg/kg) and halothane, respectively. Arterial blood pressure and blood gases, ECG, and heart and respiratory rates were recorded. Induction and recovery were timed and graded.

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) decreased in both groups 30 minutes after induction, compared with values at 10 minutes. From 40 to 70 minutes after induction, MABP was significantly higher in detomidine-treated horses, compared with romifidine-treated horses, although more romifidine-treated horses received dobutamine infusions. In all horses, mean respiratory rate ranged from 9 to 11 breaths/min, PaO2 from 200 to 300 mm Hg, PaCO2 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 differences between groups.

Detomidine and romifidine were both satisfactory premedicants. Romifidine led to more severe hypotension than detomidine, despite administration of dobutamine to more romifidine-treated horses. Both detomidine and romifidine are acceptable alpha2-adrenoceptor agonists for use as premedicants before general anesthesia in horses; however, detomidine may be preferable when maintenance of blood pressure is particularly important.