Page 311 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

290 PART III Therapeutic Modalities for the Cancer Patient

TABLE 16.2 Behaviors That May Be Seen with Cancer Quantitative Sensory Testing
and Cancer Therapy–Associated Pain in Objective methods to measure central sensitization secondary to
VetBooks.ir Behavior Cats and Dogs chronic pain recently have been developed in veterinary medicine.
Notes
Quantitative sensory testing (QST) consists of the measurement
Activity Decreased activity and diminished engage- of evoked responses to mechanical and thermal stimuli through
ment in the activities of daily living (playing); the use of various devices. Feasibility and repeatability studies of
altered gait or lameness can be associated these modalities have being performed in normal and osteoar-
with generalized pain but is more often thritic dogs. 76,77 Currently, published QST studies in dogs or cats
associated with limb or joint pain; quality with cancer pain exist, although the authors (MN, BDXL) have
of sleep may be adversely affected, mani- used QST to assess sensitivity associated with RT. The use of QST
festing as increased restlessness or altered and related testing modalities has significant potential to help us
sleep-wake cycles. understand the pathophysiology of cancer pain and potentially in
Appetite Often diminished with chronic cancer pain. the “cage-side” diagnosis of cancer pain–related abnormalities in
sensory processing.
Attitude Any change in behavior can be associated
with cancer pain—aggressiveness, dullness,
shyness, ‘clinging,’ increased dependence. Drugs and Strategies Used for Management
Facial expression Head hung low and squinted eyes in cats. Sad of Pain in Cancer Patients
expression in dogs, head carried low.
Grooming Failure to groom can result from a painful oral The drugs that can be used for chronic cancer pain management are
lesion or generalized pain. listed in Tables 16.4 and 16.5. The following discussions are not a
comprehensive appraisal of each class of drug, but rather are sugges-
Response to palpation (One of the best ways to diagnose and monitor tions for their use for cancer pain. Fig. 16.1 presents an assessment
pain.) Pain can be elicited by palpation of and treatment scheme to help the reader easily devise a strategic
the affected area, or manipulation of the
affected area, which exacerbates the pain plan to manage pain in cancer patients. If pain scores improve after
present. This is manifested as an aversion the initial base treatment, an analgesic ladder or a reverse pyramid
response from the animal (i.e., the animal approach can be applied (i.e., the number and dosages of drugs
attempts to escape the procedure, or yowls, administered can be reduced). If pain persist, a more aggressive and
cries, hisses, or bites). multimodal analgesic strategy must be implemented. The adjunc-
tive drugs listed in this scheme can be used on their own, or poten-
Respiration May be elevated with severe cancer pain.
tially two “base” analgesics could be combined (e.g., an NSAID
Self-traumatization Licking at an area (bone with primary bone and acetaminophen). However, the way this influences the side
cancer, the abdomen with intraabdominal effects likely to be seen is unknown, except in the case of NSAIDs
cancer) can indicate pain. Scratching can plus steroids, a combination known to increase the risk of serious
indicate pain (e.g., scratching at cutaneous adverse events (gastrointestinal ulceration). Euthanasia should be
tumors, scratching and biting at the flank considered only when pain persists and significantly affects the
with prostatic or colonic neoplasia).
patient’s QOL or when the necessary analgesic relief caused unac-
Urinary and bowel Failure to use litter box (cats); urinating and ceptable side effects (e.g., moribund, unresponsive, comatose).
elimination defecating inside (dogs).
Vocalization Vocalization is rare in response to cancer pain Nonsteroidal Antiinflammatory Drugs
in dogs and cats; however, owners of dogs
often report frequent odd noises (whin- NSAIDs are commonly the first line of treatment in cancer pain.
ing, grunting) associated with cancer pain. Several excellent reviews on NSAID use in small animals have
Occasionally cats will hiss, utter spontane- been published, and the reader is referred to these. 72,78–82 The
ous plaintive meows, or purr in association choice of available NSAIDs can be bewildering, but a few key
with cancer pain. points should be kept in mind.
• On a population basis, all NSAIDs are probably equally effica-

cious in relieving pain; however, for a given patient, one drug
often is more effective than another.
did not uncover any effects of osteoarthritis pain. Recent work • Gastrointestinal side effects associated with NSAID use appear
has extended our understanding of factors affecting accelerometer to be more common with drugs that preferentially block
74
output in dogs. Accelerometry is performed in client-owned COX-1 over COX-2.
animals, in their home environments, with the accelerometers • No difference in renal toxicity is seen between COX-1 selective
mounted on collars. Human chronic cancer patients with pain drugs and COX-2 selective drugs.
are more likely to present with sedentary behavioral patterns and • Liver toxicity can occur with any NSAID.
fatigue. Similar studies have not been performed in small ani- • No NSAID is completely safe, but the approved NSAIDs are
75
mals with cancer, but accelerometry and activity measures hold significantly safer than the older, nonapproved NSAIDs.
promise as a tool to assess pain and cancer-related changes in • Longer term or continuous NSAID use appears to be more
80
activity. Approximately 10 activity monitors are marketed specifi- effective than short-term or reactive use ; however, when the
cally for small animals, although current understanding of what disease is relatively stable, gradual dose reduction may be pos-
the output of each activity monitor actually relates to is limited. sible while maintaining efficacy. 69