Objective—To evaluate the local analgesic effect of
ketamine in a palmar digital nerve block at the base of
the proximal sesamoid (abaxial sesamoid block) in
Animals—36 mature healthy Andalusian horses.
Procedure—Horses were randomly assigned to 4
groups of 9 horses each and received an abaxial
sesamoid block in a randomly chosen forelimb with 1
of the following: saline (0.9% NaCl) solution, 1% ketamine
solution, 2% ketamine solution, or 3% ketamine
solution. To determine analgesia, the radiant
heat lamp-hoof withdrawal model was used as a noxious
thermal stimulus. Before each nerve block, baseline
hoof withdrawal reflex latency (HWRL, time
between lamp illumination and withdrawal of the
hoof) was determined; after the nerve block, local
analgesic effects were determined by measuring
HWRL at 2 and 5 minutes after injection and then
every 5 minutes for a total period of 1 hour.
Results—Significant differences in HWRL were
found between baseline values and values at 2 to 15
minutes following a nerve block with ketamine.
Significant differences were found between HWRL
values at every time point from 2 to 10 minutes following
a nerve block with saline solution, compared
with 1 or 2% ketamine solution. Similarly, significant
differences were found between HWRL values at
every time point from 2 to 15 minutes following a
nerve block with saline solution, compared with 3%
Conclusions and Clinical Relevance—Abaxial
sesamoid block with ketamine ensures adequate
analgesia in horses with an onset of action of 2 minutes
and a maximal duration of action of 15 minutes.
(Am J Vet Res 2003;64:475–478)
Objective—To evaluate the duration of effects on movement patterns of horses after sedation with equipotent doses of xylazine hydrochloride, detomidine hydrochloride, or romifidine hydrochloride and determine whether accelerometry can be used to quantify differences among drug treatments.
Animals—6 healthy horses.
Procedures—Each horse was injected IV with saline (0.9% NaCl) solution (10 mL), xylazine diluted in saline solution (0.5 mg/kg), detomidine diluted in saline solution (0.01 mg/kg), or romifidine diluted in saline solution (0.04 mg/kg) in random order. A triaxial accelerometric device was used for gait assessment 15 minutes before and 5, 15, 30, 45, 60, 75, 90, 105, and 120 minutes after each treatment. Eight variables were calculated, including speed, stride frequency, stride length, regularity, dorsoventral power, propulsive power, mediolateral power, and total power; the force of acceleration and 3 components of power were then calculated.
Results—Significant differences were evident in stride frequency and regularity between treatments with saline solution and each α2-adrenoceptor agonist drug; in speed, dorsoventral power, propulsive power, total power, and force values between treatments with saline solution and detomidine or romifidine; and in mediolateral power between treatments with saline solution and detomidine. Stride length did not differ among treatments.
Conclusions and Clinical Relevance—Accelerometric evaluation of horses administered α2-adrenoceptor agonist drugs revealed more prolonged sedative effects of romifidine, compared with effects of xylazine or detomidine. Accelerometry could be useful in assessing the effects of other sedatives and analgesics. Accelerometric data may be helpful in drug selection for situations in which a horse's balance and coordination are important.