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 Figure 1: Allodynia, hyperalgesia vs normal stimulus response curve. Image excerpted from Bergadano3
Pain as an experience differs for each individual. Observe and adjust doses to make every patient comfortable.
Oral diseases such as periodontal disease, root exposure, resorptive lesions, stomatitis and oral
ulcers and masses are all painful. Bacterial cystitis and pyelonephritis are more frequent in older cats but the prevalence of interstitial/sterile cystitis or inflammatory bowel disease does not differ from younger cats; inadequately addressed, these may cause on-going pain. The likelihood of neoplasia increases with increasing age. The need for analgesia MUST be considered as part of any treatment plan for the older cat. “Routine” procedures including blood collection, intravenous catheter placement, restraint of a thin or arthritic patient are uncomfortable.
Recognition of chronic pain and arthritic pain is relatively recent. The incidence of degenerative joint disease (DJD) appears to be much more common than previously thought and is probably a major cause of discomfort in ageing cats. In three studies retrospectively assessing radiographs taken of cats over 12 years of age7 or of any age8,9 the prevalence of findings suggestive of DJD was 90%, 22% and 34%, respectively with older cats showing radiographic changes. Only 4%, 33% and 16.5% had notation of restricted mobility in the medical record indicating that appropriate questions were not being asked of owners, that cats do not experience or that they don’t show discomfort from these joint changes.
A recent study10 prospectively evaluated cats of all ages to determine the prevalence of radiographic signs of DJD. Most (92%) cats had radiographic evidence of DJD; 91% had at least 1 appendicular site affected and 55% had > 1 site of axial DJD. Affected joints in descending
order of frequency were hip, stifle, tarsus, and elbow. The thoracic segment of the spine was more frequently affected than the lumbosacral segment. Grading the severity of each of the radiographic changes identified, they found that for every 1-year increase in age, the expected total DJD score increased by an estimated 13.6%. They concluded that radiographically visible DJD is very common in domesticated cats, even in the young and is strongly associated with age.
Yet lameness is not a common clinical sign of this problem in cats: signs are insidious or often attributed to ageing. They include inappropriate elimination (often adjacent to the litter box), decreased grooming, developing antipathy for being combed, reluctance to jump up or down, sleeping more, moving less, withdrawing from human interaction, and possibly even hiding. When activity monitors were attached to cats’ collars, activity counts increased with meloxicam suggesting alleviation of musculoskeletal discomfort11.
Wherever possible, the underlying cause of the pain should be identified and corrected.
Because cats are solitary survivors, they are notoriously secretive in revealing discomfort and disabilities. When the presenting concerns from the client fail to include observations of pain, questions regarding behavioural or life-style changes may elicit clues. Changes in awareness, personality and interaction, an inappropriate activity level, reduction in playing, aggression, changes in sleeping patterns and litter box use may be present. Other indicators of on-going pain include a decrease in mobility or ease of jumping (up or down), inappetence or altered eating behaviours and a poor coat from
lack of grooming12. Adults and older individuals are generally more stoic making it even harder to detect pain than in the kitten. Seriously ill or obtunded patients are especially difficult to assess for pain as they are less likely to display behavioural signs of distress when compared to an otherwise healthy injured cat13.
Examination may reveal reluctance to being handled or having a particular body part palpated or manipulated and may result in self-defensive behaviour. Sedation/ anaesthesia may be needed to properly assess oral and dental problems or for imaging. Radiographic, ultrasonographic or advanced imaging (MRI/CT) may be warranted to identify the underlying problem. Quantitated sensory testing may be undertaken to help localize the neuropathic lesion using different types of stimuli to identify the type (and therefore location) of nerve fiber affected2.
Elimination trials may be undertaken to verify and alleviate pain. For example, a local block may be used to assess oral/dental problems or a regional block for a joint or paw. An analgesic trial, usually based around opioids with or without non-steroidal anti-inflammatory
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