Objective—To compare detomidine hydrochloride
and romifidine as premedicants in horses undergoing
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
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.
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) 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.
Conclusions and Clinical Relevance—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 α2-adrenoceptor agonists for
use as premedicants before general anesthesia in
horses; however, detomidine may be preferable
when maintenance of blood pressure is particularly
important. (Am J Vet Res 2001;62:359–363)