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Acute and chronic pain in cats, part one

Mathews KA, Kronen PW et al.  WSAVA guidelines for recognition, assessment, and treatment of pain. J Small Anim Pract 2014;55:E10-68.

This is a summary of Section 1 (“Introduction to pain, its recognition and assessment”) of this document as it pertains to the cat.  The document is the work of the World Small Animal Veterinary Association’s (WSAVAC)  Global Pain Council (GPC), an international consortium of specialists whose goal is to help the veterinary profession identify pain as the fourth vital sign and minimize pain prevalence in and impact on small animal patients.

Basic tenets of the document applicable to all small animal patients include:

(1) Pain is an illness, experienced by all mammals, and can be recognized and effectively managed in most cases

(2) Pain assessment should accompany every patient assessment

(3) Treat predictable pain; pain associated with surgery is 100% predictable

(4) Pain assessment is key to determining the degree and duration of pain treatment but should not replace the mandate to treat predictable pain

(5) Perioperative pain extends beyond 24 hours and should be managed accordingly

(6) Practice pre-emptive pain management; initiate appropriate treatment before a procedure to prevent the onset of pain, and continue this to prevent the occurrence of pain for the duration of time commonly recommended for the problem or which the patient requires

(7) Response to appropriate treatment is the gold standard to measure the presence and degree of pain

(8) We cannot always know that our patient does hurt, but we can do our best to ensure that it does not hurt.

The initial portions of the document define and describe pain, types of pain, and the physiology and pathophysiology of pain. With regard to recognition and assessment of acute pain in cats, the document references a validated multidimensional composite pain scale (UNESP-Botucatu) for assessing postoperative pain in cats.  A website describing this pain scale along with visual features and self-evaluation tools is available. In assessing acute pain in cats, prior knowledge of the cat’s normal behavior is very helpful.  Initially a potentially acutely painful cat should be observed from a distance.  Then, if possible, the caregiver should interact with the cat and palpate the painful area.  Cats should not be awakened to assess their pain status; rest and sleep, as long as the cat is in a relaxed, curled-up normal-looking posture, is a good sign of comfort.

Types of facial expressions demonstrated by cats in pain can include a furrowed brow, orbital squeezing (“squinty” look), and a head hanging downward.  Some cats will be very still either because they are afraid or too painful to move.  A previously friendly cat who displays aggression, is hiding, or tries to escape may be in significant pain.  Cats displaying a hunched position and/or a tense abdomen following abdominal surgery are likely in pain.  Sitting or lying in abnormal positions, abnormal gait or weight shifts on the part of the patient may reflect discomfort and protection of a painful area.  Behavioral clues to acute pain in cats include reduced activity, loss of appetite, quietness, hiding, hissing and growling, excessive licking of a specific area of the body, cessation of grooming, tail flicking, and aggression.  Cats in severe pain are usually depressed, immobile, and silent, and will usually appear tense and distant from their environment.  During the early postoperative period (20-30 minutes) signs of dysphoria including thrashing, restlessness, and continuous activity, may be hard to distinguish from signs of severe pain.

When a cat is in chronic pain, the behavioral changes associated with this condition may develop gradually and be subtle, so owner observations and assessment are likely to be quite valuable in this regard, since the owner is most familiar with the animal. Owner assessments are currently the mainstay of chronic pain assessment in dogs, and a number of validated instruments are available for this.

Chronic pain is generally associated with chronic diseases such as degenerative joint disease, stomatitis, intervertebral disk disease, and neoplasia, or it may be associated with pain persisting beyond the expected course of an acute disease process or surgery, such as an amputation or onychectomy. An owner-directed assessment for chronic musculoskeletal pain in cats is under development, but at this time there are no validated instruments available.  Behaviors in cats potentially in chronic pain should be assessed in the following categories, and owners are most likely to be able to monitor these ongoingly:  general mobility (ease of movement, fluidity of movement, performing activities (playing, hunting, jumping, using the litterbox), eating and drinking, grooming, resting, observing, and relaxing (are these activities enjoyed by the cat?), social activities involving people and other pets, and temperament continuity or changes.  Each of these behaviors should be assessed and “scored” in some way—either descriptively or using a numerical or visual analogue scale, that is re-evaluated over time and vis-a-vis any pain management strategies offered.

Effective pain management includes assessment of response to treatment of pain.  When evaluating pain management effectiveness in an animal patient, a baseline assessment of pain level should be made at the first visit, and then at subsequent evaluations, it is essential to interact with the animal and use a knowledge of normal behaviors as well as behaviors associated with pain.  The owner should be involved in ongoing assessment of pain and response to treatment through effective open questioning techniques. Assessments should be repeated on a regular basis.  With potential acute postoperative pain, cats and dogs should be assessed every 15-30 minutes in the early recovery period (depending on the surgical procedure), then hourly thereafter for the first 6-8 hours after surgery.  Thereafter, if pain is well controlled, assessment should be performed every 3-6 hours.

Chronically painful cats and dogs should be assessed regularly, using owners as a key information source, prompting them to report changes in the pet’s behavior that they may not necessarily view as associated with chronic pain.

Subsequent portions of the first section of the document address neuropathic pain, which can develop in conjunction with any chronic pain condition, and perceived levels of pain associated with various conditions and procedures.  Section 1 concludes with discussion of some common pain misconceptions:

(1) Opioids—they do not cause respiratory depression in healthy cats and dogs; in sick animals, these drugs should be titrated to effect to minimize the risk of respiratory compromise.  For opioid-related respiratory compromise to occur, the patient must be markedly mentally depressed.

(2) NSAIDs are not necessarily toxic to animal patients.  As most pain is associated with inflammation, NSAIDs are a mainstay of analgesia for both acute and chronic pain in dogs and cats.  Individual patients must, however, be screened for potential risk factors and monitored during treatment. Where NSAIDs approved for animal patients are available, they should be used preferentially.

(3) Pain should not be used as a strategy to restrain the patient from self-trauma following surgery or injury.  Other methods of restraint to stop self-injury should be used in conjunction with adequate and appropriate pain management.

(4) Animals of all ages feel pain, including newborns and infants.

(5) Appropriate use of analgesics eliminates pain as a potential cause of signs of patient deterioration.

(6) Most anesthetics in common use (inhalants, propofol, barbiturates) do not act as analgesics.  They block conscious perception of pain, but nociception is still occurring while the patient is unconscious and the pain generated during this time will be experienced upon awakening. [PJS]

See also:
Brondani JT, Mama KR, et al.  Validation of the English version of the UNESP-Botucatu multidimensional composite pain scale for assessing postoperative pain in cats.  BMC Veterinary Research (electronic resource) 2013;9:143.

Downing R.  Pain management for veterinary palliative care and hospice patients.  Veterinary Clinics of North America Small Animal Practice 2011;41:531-50.