Page 52 - WSAVA2018
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 25-28 September, 2018 | Singapore
M. Scherk1
1Dip ABVP (Feline Practice), Vancouver, Canada
Over the recent decade, there has been increased awareness of pain and attention to the alleviation of pain in cats. Investigation has focused primarily on chronic musculoskeletal pain. The purpose of this presentation is to address other types of chronic and neuropathic pain in cats. For an excellent review of all types of pain, the reader is referred to the WSAVA Guidelines for recognition, assessment and treatment of pain1.
Pain isn’t just about how it feels; it is also about how it makes you feel. It results in suffering and a feeling of hopelessness. According to the International Association for the Study of Pain, pain is an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Pain may be nociceptive, associated with injury
(thermal, chemical or traumatic/surgical), inflammatory or neuropathic. There is a lot of overlap, and, regardless
of type, if adequately controlled and primary or secondary inflammation resolve, pain should not become irreversible.
Acute pain is associated with tissue damage and
serves to change behaviour in order to minimize
or avoid damage. It is beneficial in that it helps to optimize conditions in which healing can take place.
It is self-limiting and stops once healing is complete. Chronic pain, on the other hand, persists beyond the expected healing process without a clear end-point. It
is maladaptive and dysfunctional and does not support healing. It can have significant effect on physical wellbeing and psychology of the sufferer. Chronic pain may be considered a disease state. Chronic pain may
be present as a result of ongoing medical inflammation (e.g., intestinal, lower urinary tract, oral/dental, musculoskeletal) or secondary to unrelenting nociceptive stimulation (injury and associated inflammation).
Neuropathic pain is a term that refers to pain that is directly caused, or instigated, by dysfunction of, injury to, or primary lesion in the nervous system. As damaged nerves fire spontaneously, they become hyper- responsive to even normal stimuli. This pathophysiology results from sequential changes occurring in the peripheral nervous system, spinal cord, brainstem and brain1.
Neuropathic pain is often a result of surgery, especially amputations (e.g., tail, limb, onychectomy) or fractures when appropriate analgesic agents have not been used or used for a long enough duration. Nerve compression and diabetes also result in neuropathic pain as can
any chronic, unrelenting pain regardless of cause2. Neoplasia, and probably interstitial/sterile idiopathic cystitis, are considered to be “mixed” as they have both inflammatory and neuropathic characteristics.
Tissue damage stimulates the nociceptors; this results in transduction (i.e., translation of the stimulus), transmission of the signal to the spinal cord where it is modulated (amplified or dampened) and then transmitted to the brain where the original stimulus is ultimately perceived (in the frontal cortex and limbic system). Therefore, it is likely that emotional and psychological elements play a role in cats as they do in people3.
Acute pain must be treated until inflammation is sufficiently resolved that the pain pathway won’t be aggravated anew. All patients need to be sent home
with analgesic medication post-operatively, regardless
of how “routine” the procedure is4-6. If inadequate analgesia was provided following surgery or other trauma, or wasn’t administered for long enough, permanent changes to the central nervous system may occur resulting in the patient experiencing excessive and inappropriate pain. Persistent nociceptive input results in “wind-up”, an increase in the excitability of the sensory neurons of the spinal cord. These hyperexcitable cells amplify the signal that is sent to the brain resulting in changes to receptors and a decrease in inhibitory signals descending from the brain. Thus, the patient has a lower threshold to pain, experiencing it at a lower intensity than is expected (“allodynia”), has a greater pain response, experiencing more pain than expected for a given stimulus (“hyperalgesia”), and may have pain over wider regions than expected. In other words, it is important,
not only to provide pain relief, but to provide it for a long enough period3. (See Figure 1.)

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