Chronic Pain in Cats

Pain that persists over weeks, months and sometimes years is associated with diseases such as degenerative joint disease, stomatitis and other oral pathology, interstitial cystitis and some forms of cancer. However, pain may be present in the absence of ongoing clinical disease, for example persisting beyond the expected healing time of an acute disease process; examples of this include neuropathic pain following limb or tail amputation. Chronic pain has a negative impact on a cat's quality of life (QoL). In recent years, treatment options for some cancers in companion animals have become a viable alternative to euthanasia, and managing chronic pain and the impact of aggressive treatment protocols has become a challenging and important welfare issue.

Pain recognition and assessment are key to effective pain management. The behavioral changes associated with chronic pain often develop gradually and may be subtle and easily overlooked both by owners and veterinarians. In most cases, these changes are most obvious to someone familiar with the animal, usually the owner, but they may need prompted to think about how their pet's behavior has changed over the months and years. Many owners mistake pain for "just getting old."

Assessment tools for long-term pain and its impact are essential, but how these tools should be constructed optimally for cats is not yet fully understood. Many of the tools for measuring chronic pain in humans measure the impact of pain on the patient's overall QoL and encompass both physical (how it feels) and psychological aspects (how it makes you feel). There is a growing understanding of behaviors that may be related to painful musculoskeletal disease in cats.¹ An owner-directed instrument for the assessment of chronic musculoskeletal pain in cats has been developed and tested^2-4 and what owners consider important for their cat's quality of life has also been investigated⁵.

Assessments may need to be individualized based on the cat's lifestyle (e.g., indoor versus outdoor); however, behaviors can be assessed in the following broad categories:

 General mobility

 Performing activities (playing, jumping, using a litter box)

 Eating, drinking

 Grooming

 Social activities involving people and other pets

 Temperament

Each of these should be assessed and recorded. Re-evaluation over time will help determine the impact of pain; whether or not the disease process is stable, worsening or improving; and the efficacy of treatment. It may be helpful to have owners keep a diary of their cat's activity and behaviors so they can look back and see how things have changed. Additionally, photographs and videos can be dated and catalogued. It is very helpful if owners record videos of their cat in their home environment (easily done with a smartphone) where they are relaxed and in a familiar environment. In many cases, it is difficult to perform an orthopedic examination on a cat in the hospital or clinic environment, as they may be unwilling to explore and move freely due to the unfamiliar environment. In addition, seeing home videos may give the practitioner insight into how to improve the cat's home environment to enhance enrichment and ease of access to important resources (e.g., litter boxes, favorite elevated resting places).

Chronic Pain in Dogs

As dogs live longer, the practitioner is faced with treating a large population of dogs with osteoarthritis (OA) and also pain related to cancer and related treatments. Treatment options for chronic pain are complex, and response to treatment varies greatly from patient to patient, so it is important to accurately assess pain and QoL on a regular basis.

Behavioral changes associated with chronic pain in dogs may develop gradually and be subtle; therefore, the owner must be involved in the assessment. There are tools available to evaluate chronic pain. The categories that should be assessed include:

 Vitality (e.g., energy, activity)

 Mobility (e.g., tolerance to exercise, stiffness, lameness)

 Mood and demeanor (e.g., alertness, anxiety, playfulness)

 Levels of distress (e.g., vocalization, response to other pets and humans)

Questionnaires have been developed to assess health-related (HR) QoL in dogs with chronic pain.^6,7 At the present time, the most fully widely used instruments are:

 GUVQuest

 Canine Brief Pain Inventory

 Helsinki Chronic Pain Index

 Texas VAS Instrument

 Liverpool Osteoarthritis in Dogs

GUVQuest is an owner-based questionnaire developed using psychometric principles for assessing the impact of chronic pain on the HR QoL of dogs, and validated in dogs with joint disease and cancer. The Canine Brief Pain Inventory (CBPI) has been used to evaluate improvements in pain scores in dogs with OA and in dogs with osteosarcoma. The Helsinki Chronic Pain Index (HCPI) is also owner-based and has been used for assessing chronic pain in dogs with OA. The Liverpool Osteoarthritis in Dogs ('LOAD') clinical metrology instrument has been validated in dogs with chronic elbow OA.⁸

From these studies, some key information has emerged:

 Owner information is very valuable when assessing chronic pain

 Owners may need prompting and questioning before they report changes in their dog's behavior, as they may associate these changes with old age rather than with chronic pain

 Changes in behaviors may be subtle and take place gradually. Veterinarians need to ensure that when questioning the owner, they prompt owners to reflect over a period of time (weeks and months)

 The veterinarian may find it useful to identify behaviors from the owner that can be used as marker behaviors to help determine response to treatment; for example, how far the dog is willing to walk or how willing it is to engage in play.

Because osteoarthritis is the most common cause of long-term pain in dogs and may affect at least 25% of the canine population, it is important to be competent in assessment of this disease. Evaluating the canine OA patient consists of a combination of assessments and examinations by the veterinarian and the owner.

The overall assessment of the negative impact of OA on the patient involves an evaluation of four main categories:

 Mobility (the quality of moving freely)

 Activity (the ability to perform specific activities)

 Pain (adverse sensory and emotional experience)

 Affective states (mood, emotions and feelings)

Careful assessment of these four categories will guide treatment strategies. To fully assess the patient, gather information about:

 Body balance, muscle mass (e.g., measure limb circumference)

 Ease of movement and mobility

 Gait and limb use

 Joint-associated pain

 Joint range of motion

 Other factors that affect mobility (e.g., rule out neurological disease and cruciate ligament injury)

 Ability to perform specific activities

 How content or happy the dog is

Such a complete assessment will involve input from both the veterinarian and the owner, and this data then forms a baseline for future (re)assessment after intervention.

References

1.  Bennett D, Morton C. A study of owner observed behavioural and lifestyle changes in cats with musculoskeletal disease before and after analgesic therapy. J Feline Med Surg. 2009;11(12):997–1004.

2.  Zamprogno H, Hansen BD, Bondell HD, Sumrell AT, Simpson W, Robertson ID, et al. Item generation and design testing of a questionnaire to assess degenerative joint disease-associated pain in cats. Am J Vet Res. 2010;71(12):1417–1424.

3.  Benito J, Depuy V, Hardie E, Zamprogno H, Thomson A, Simpson W, et al. Reliability and discriminatory testing of a client-based metrology instrument, feline musculoskeletal pain index (FMPI) for the evaluation of degenerative joint disease-associated pain in cats. Vet J. 2013;196(3):368–373.

4.  Benito J, Hansen B, Depuy V, Davidson GS, Thomson A, Simpson W, et al. Feline musculoskeletal pain index: responsiveness and testing of criterion validity. J Vet Intern Med. 2013;27(3):474–482.

5.  Benito J, Gruen ME, Thomson A, Simpson W, Lascelles BD. Owner-assessed indices of quality of life in cats and the relationship to the presence of degenerative joint disease. J Feline Med Surg. 2012;14(12):863–870.

6.  Wiseman-Orr ML, Nolan AM, Reid J, Scott EM. Development of a questionnaire to measure the effects of chronic pain on health-related quality of life in dogs. Am J Vet Res. 2004;65(8):1077–1084.

7.  Wiseman-Orr ML, Scott EM, Reid J, Nolan AM. Validation of a structured questionnaire as an instrument to measure chronic pain in dogs on the basis of effects on health-related quality of life. Am J Vet Res. 2006;67(11):1826–1836.

8.  Hercock CA, Pinchbeck G, Giejda A, Clegg PD, Innes JF. Validation of a client-based clinical metrology instrument for the evaluation of canine elbow osteoarthritis. J Small Anim Pract. 2009;50(6):266–271.