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)