Chapter 19 The Prevention and Management of Pain in Canine Patients 485(Hay Krause, 2014), and its use as a premedi-
cant is increasingly routine. There is some evi-
dence, however inconclusive at this time, that
maropitant may have a pain‐modifying effect
as well (Boscan et al., 2011). Treatment strate-
gies for opioid‐induced dysphoria include
buprenorphine (displaces pure mu agonists
from the receptor), butorphanol (antagonizes
the mu receptor but activates the kappa recep-
tor), or a microdose of dexmedetomidine; all
will diminish dysphoria while maintaining
some degree of analgesia.
Oral opioids are recommended for many
chronic pain conditions in humans, including
OA (American Pain Society, 2002), although it is
now accepted that overprescription of strong
oral opioids has led to serious problems of
dependence and addiction. While to date there
are no clinical data supporting the use of oral
opioids in dogs, their intermittent, judicious
use (+/– combined with acetaminophen) can be
considered for dogs experiencing breakthrough
pain in acute and chronic pain states, and/or as
palliative end of life care.
Locoregional anesthesia
Local anesthetics (LAs) are the principal means
used to reduce pain and to provide general
anesthesia and concurrent analgesia; they are
also used for their anti‐inflammatory and anti-
microbial activity (Cassuto et al., 2006; Johnson
et al., 2008). They are considered quite safe at
customary doses. Most techniques are easily
mastered, and inexpensive. There no longer
exists a rationale against local/regional anes-
thesia as part of every surgical intervention
(Jones, 2008). The 2015 AAHA/AAFP Pain
Management Guidelines stipulate that insofar as
possible, LAs should be utilized with every sur-
gical procedure (Epstein et al., 2015).
LAs bind to a hydrophilic site within sodium
channels, thus blockading them; without a Na+
influx, neurons may not depolarize. The effect is
complete anesthesia to a site rather than analge-
sia. Different LAs will have variable onsets,
durations of action, and toxicities. A general
limitation of LAs is a relatively short duration
(hours) of action. This can be overcome in a
variety of ways, including the addition of a
small amount of opioid (Bazin et al., 1997)
or alpha‐2 agonist (Hu et al., 2017) to the LA, and
the use of wound diffusion catheters. In 2017, a
novel liposome‐encapsulated bupivacaine
product (Nocita®) was introduced for dogs,
labeled for 3 days of postsurgical analgesia.
LA is limited only by the clinician’s ability to
learn various techniques and anatomic land-
marks. Blocks include: local line or parainci-
sional; subcutaneous infiltrative; intrapleural,
intra‐abdominal; retrobulbar; intratesticular,
intra‐articular, carpal ring, epidural, sacrococ-
cygeal, dental (orofacial), brachial plexus, inter-
costal, paravertebral, and wound diffusion
catheters. A rapidly expanding modality is the
use of ultrasound and nerve electrolocator
devices to enhance precision and dose in
perineural delivery for peripheral nerve block-
ade. Comprehensive discussions of the many
techniques are now available (Campoy & Read,
2013; Lerche et al., 2016).Tips for use
The edge in efficacy goes to preoperative use
(Savvas et al., 2008), but infiltration of LAs
postincisionally can be effective. To minimize
the sting of administration in awake patients,
the LA is warmed to body temperature and
injected slowly (Hogan et al., 2011); mepiv-
acaine appears to elicit less sting than either
lidocaine or bupivacaine. Diluting the LA (with
saline to increase the volume for large infiltra-
tive areas) will slow the onset and shorten the
duration of action.
Toxicity is most likely to occur when admin-
istration occurs at very large doses and/or
intravenously (which must be avoided with the
potentially cardiotoxic bupivacaine). LAs can
result in motor as well as sensory blockade (a
special consideration with epidurals). There is
little clinical evidence to support the belief that
LAs impair wound healing or promote postop
infection—in fact LAs are antimicrobial.
To facilitate catheter placement or other
minor skin procedures, a transdermal LA for-
mulation, EMLA®, that also comes as a generic,
LMX4, may be placed on a shaved area and
covered with a bioadhesive dressing or other
nonporous wrap (e.g., foil). Although penetra-
tion has been reported to be time‐dependent
(Wahlgren & Quiding, 2000), 20 minutes
appears sufficient in canine patients.