Small animal - March 2023

Detecting pain in cats is difficult for clinicians as cat behaviour makes pain assessment more challenging. It is in their nature to mask signs as an adaptive survival strategy. In addition, owners are often not able to understand that their pet may be in pain as the disease may be undetected, for example dental disease. Owners may feel their pet is naturally ageing and not suffering from pain, for example in older cats with osteoarthritis. It is important to communicate clearly with an owner in order to successfully make them understand that their pet is painful. Directly comparing the patient’s scenario to a human one can be useful to help owners understand their pet better.

Pain is a physiological response to noxious stimuli and consists of a sensory and motor component as well as cognitive and emotional components. A negative emotional state can influence perception of pain, therefore as clinicians we should be doing all that we can to avoid negative emotions in feline patients both in the hospital and the home, using appropriate handling techniques and managing the environment (see Tables 1 and 2). 

It is generally easier for clinicians to diagnose acute pain compared to chronic pain. Acute pain is due to tissue damage, frequently from trauma or inflammatory conditions. It resolves once the tissue has repaired and healed. Chronic pain is a maladaptive response of the central nervous system and persists after tissue healing. It is characterised by a mixed nociceptive input (chronic inflammatory, neuropathic and/or functional pain) that can occur due to disease or injury or occurs by itself. Chronic pain has no clear end point unlike acute pain.

In a clinic setting, it can be difficult to examine cats completely as their posture is likely to be different on a consulting room floor or table compared to their home environment. Protective (previously described as negative) emotions may be activated that are not present in the home or cats may appear frozen. Chronic pain may not become apparent in a physical examination therefore careful discussion with the owner is needed. Discussing specific behavioural changes and mobility changes can be a good indicator of the presence of chronic pain in cats. Specific behaviours can include changes to the use of litter trays (for example no longer using the tray at all, eliminating adjacent to the tray, taking extra time to get in or out of the tray or taking longer to eliminate while in the tray), changes to resting areas (for example, reluctance to go up or down stairs or on/off furniture), changes to grooming behaviour (unable to comfortably groom certain areas, therefore becoming unkempt), changes to feeding/drinking habits (the positioning of bowls can make it difficult for a cat with osteoarthritis to access resources) or changes to interaction with the owner (cats can become more withdrawn or clingy). Video footage of the animal moving or eating, for example, may be useful to help examine the patient for evidence of chronic pain.

Acute pain assessment

As clinicians we can be confident that the patient will be suffering from pain in obvious scenarios, for example a traumatic incident (see Table 3). Using a scoring system can help the veterinary team monitor a patient for pain or monitor the response to the administration of analgesia. Scoring systems can also assist in the consideration of pain in disorders where the detection of pain is more difficult.

The Feline Grimace Scale (FGS) is a facial expression-based scoring system for acute pain assessment in cats. It considers five facial factors, called action units (AU) and assigns them a score (see Table 4 and Figure 1).

The final score is calculated by adding the scores for each unit and dividing this total by the maximum possible score (10 if all five action units are scored).  Analgesia is recommended when the final score is four out of 10 or more. This provides a user-friendly, quick method to assess the presence of pain in the feline patient.

The 'Glasgow Composite Measure Pain Scale - Feline' is another tool commonly used in first opinion practice. As well as calculating scores based on the patient’s facial expression, the operator completes a simple questionnaire with scored answers and analgesia titrated based on the findings. It includes 28 descriptor options within seven behavioural categories. Users should follow the assessment procedure as described in the the Glasgow Feline Composite Measure

Pain Scale questionnaire.

The maximum score is 20 and analgesic intervention is recommended when the individual’s score is five or more.

These guides can be downloaded and printed to have to hand in the ward environment. They provide a consistently reproducible method to record pain and can be used by different team members to manage the patient. They can also be used to monitor the response to any analgesics administered and allow these to be titrated if needed or additional agents may need to be introduced to the treatment plan.

Chronic pain assessment

Many disorders can cause chronic pain, which can result in changes in the modulation of pain signals, hyperalgesia (an enhanced sensitivity to pain) and allodynia (pain elicited by a stimulus that does not normally cause pain) (see Table 5).

While it may be possible to determine chronic pain from the physical examination in some cases, other causes will remain undetected. Discussing behavioural changes with the owner can be used to determine whether pain is present and also to determine the response to any treatment or environmental changes (see Table 6).

Medications used routinely in pain management in first opinion practice

There are numerous drugs available in feline practice to provide analgesia (see Table 7 which runs from page 140 to 142). The concept of multimodal analgesia, using different drugs with different modes of action, provides optimal pain relief in most scenarios. Butorphanol provides excellent sedation but has poor analgesic properties, so should not be used for painful conditions.

Other medications such as tramadol, amantadine and amitriptyline have been used in the management of pain in cats. However, proof of efficacy of these medications is lacking and it is best to consider drugs listed in Table 7 first. Clinicians should keep up to date with developments in analgesia, as this is an area undergoing frequent research and product development.

Adjuncts to analgesia

There are additional measures we can consider for hospitalised patients with pain to make them feel more comfortable and to reduce the potential for negative emotions:

• Cardiovascular support (for example intravenous fluids and oxygen supplementation).
• Support for fractures or wounds (bandaging and dressings).
• Careful surgical techniques and tissue handling.
• Use of muscle relaxants to reduce muscle spasms, for example, in urethral spasm.
• Reduce anxiety through sympathetic handling and provision of a quiet environment.
• Ensure the environment is at an appropriate temperature, with ambient lighting and provision of dark periods. Try and keep food and water bowls apart from each other and from the litter tray.
• Ensuring patient bedding provides adequate support.
• Ensure the kennel and containers are cleaned regularly, and the patient groomed, if tolerated and sufficient nursing time provided.
• Nutritional support can make a patient feel more comfortable and assist wound healing.
• Monitor the patient’s faecal and urine output. Clean the perineal area if needed and provide support where needed.
• Use gentle physiotherapy, for example, massage or passive range of motion exercises.
• Consider alternative forms of therapy, for example, acupuncture.

For animals with acute and chronic pain managed in the home setting, a number of factors listed above can be considered. Environmental modification to ensure patient comfort should always be discussed. Clinicians should not assume that owners will automatically know what simple measures they could take in order to improve their pet’s quality of life.

Environmental modification is usually required. For example, introducing a number of steps/blocks/boxes can help the cat get comfortably from the floor to a sofa or bed. Consideration of comfortable bedding material providing patient support is important. Raising the food and water bowls may reduce strain on the musculoskeletal system and increase food and water intake.

Obesity can lead to an increase in chronic pain, therefore weight control is important. Environmental enrichment and physical therapy can help with this, as well as monitoring the pet’s diet. Owners may need to avoid providing excess enrichment however, for example, providing lots of toys the cat can not effectively use. This may lead to arousal in an individual who is unable to use the toys appropriately and subsequently leads to frustration in the patient.

There has been an increase in use of alternative therapies, such as acupuncture or electromagnetic field therapy. This may be useful in an individual, but there is no data available currently in cats.

Specific diseases that cause chronic pain

Osteoarthritis

Owners who may consider that their pet is merely getting older commonly disregard signs of osteoarthritis. It is primarily inflammatory pain but can also involve neuropathic pain. The hip, stifle, shoulder, elbow, tarsus and spine are most commonly affected.

Cats with osteoarthritis do not often limp and are more likely to have changes in their gait and reduction or alteration in behaviours or interactions with the owner. The patient may withdraw from the owner, the owner’s touch or may become clingier. Aggression can occur to the owner or other animals. The patient may appear to be resting more or may be more restless. Postural changes are frequently noted with an altered standing or sitting posture common. Changes in mobility are frequently detected on discussion with the owner. Difficulty using the litter tray is common and inappropriate elimination may occur. Grooming habits are frequently altered and the patient may appear matted or may overgroom painful areas.

There are a number of pain scales available to use in the assessment of osteoarthritis in cats, including the Client Specific Outcomes Measures and the Montreal Instrument for Cat Arthritis Testing.

Management of osteoarthritis

Environmental modification is an important component of the management of osteoarthritis. Simple considerations can make a marked improvement in the patient’s quality of life. As previously noted in this article, introducing a number of steps/blocks/boxes can help the cat get comfortably from the floor to a sofa or bed. Also, as previously mentioned, consideration of comfortable bedding material is important. It's also worth repeating that raising the food and water bowls may reduce strain on the musculoskeletal system and increase food and water intake.

Osteoarthritis affects individuals in different ways. There will be varying degrees of peripheral and central sensitisation, resulting in different clinical signs. Non-steroidal anti-inflammatory drugs (NSAID) are a mainstay of treatment of osteoarthritis.

Given that osteoarthritis tends to occur in older cats, concurrent diseases such as chronic kidney disease (CKD) are common. It is generally recommended to titrate the administration of NSAIDs to the minimal effective dosage based on response to therapy. This can be altered if needed, for example, in the case of an acute flare up of disease. Overweight animals should be administered a dose appropriate for their ideal weight. NSAIDs should be used with caution in patients with cardiovascular or liver disease.

Multiple studies have shown that long-term NSAID therapy is safe in cats with stable CKD. Classification of a cat with stable CKD is not fully determined, but may include minimal changes in bodyweight and creatinine over a period of months and successful management of any concurrent conditions, for example hypertension. Patients should be hydrated with consideration of multiple water resources, including water fountains and wet food. Guidelines for the management of CKD should be followed. Client education is important as the client is the primary care-giver. They should be monitoring for clinical signs including anorexia, weight loss, vomiting, diarrhoea, polyuria or polydipsia. Regular clinic-based health assessments should be performed, including weight checks and blood or urine sampling where necessary.

Meloxicam has been licensed for long-term use in cats. As a palatable liquid formulation, it is easy for most owners to administer and can be titrated to the lowest effective dose. Robenacoxib is another NSAID licensed for treatment of cats, but at a maximum of six days’ duration.

NSAIDs are beneficial in the management of peripheral sensitisation but multimodal analgesia is needed to manage animals with central sensitisation (for example, gabapentin).

Opioids may be useful for acute pain settings but are not often used in the long-term management of osteoarthritis. Tolerance and constipation are some of the most common adverse effects. Buprenorphine can be used at home via transmucosal administration and can be a useful adjunct to other pain management strategies. Gabapentin can provide additional analgesia in some cats and can be useful where neuropathic pain is present. It is mostly used as an adjunct treatment but can sometimes be used successfully as the sole agent in particular cases.

If in doubt, it is advisable to perform a therapeutic trial at home and ask the owner to score the patient’s mobility and behaviour to assess patient response.

Recently a novel therapy for the treatment of pain associated with feline osteoarthritis has been licensed in Ireland by Zoetis. Solensia (frunevetmab) is an anti-nerve growth factor (NGF) monoclonal antibody. In osteoarthritis, NGF is elevated and exerts its effects by binding to neuron and immune cells resulting in increased pain, the release of pro-inflammatory mediators (and more NGF) and neurogenic inflammation. In the treatment of osteoarthritis, monoclonal antibodies target and neutralise NGF and are eliminated via normal protein degradation pathways with minimal hepatic or renal involvement. This can allow control of pain in animals with CKD or those who do not tolerate meloxicam. Solensia is administered at a dose of 1ml for cats 2.5-7kg (2ml for cats over 7 kg) as a single subcutaneous injection once monthly.

Feline Oral Pain Syndrome

Feline Oral Pain Syndrome (FOPS) has been likened to trigeminal neuralgia in humans. Burmese and older cats are more likely to suffer from the disorder. Stress may also be involved in the disease. Oral pathology such as resorptive lesions or gingivostomatits can be associated with the disorder.

Clinical signs include pawing or traumatisation of the face, exaggerated mouth movements (such as licking) and vocalisation (such as growling when eating or grooming). Appetite changes are common and food aversion may occur. Self-mutilation of the tongue, lips or buccal mucosa can occur in more severe cases.

Multimodal analgesia is generally recommended, with gabapentin often used as the primary analgesic.

Feline hyperaesthesia syndrome

This idiopathic condition is characterised by skin twitching and muscle spasms in the lumbar area. Licking of the lumbar, flank and tail regions can occur. An exaggerated response to touch may be seen. Episodes are generally intermittent and variable. Gabapentin is frequently used, along with other medications (for example, phenobarbital, amitriptyline, NSAIDs).

Feline chronic gingivostomatitis

Feline chronic gingivostomatitis (FCGS) is a common and sometimes severe disease of undetermined aetiology. Immune-mediated response to dental plaque and various infectious organisms have been attributed to the development of FCGS. It can affect all oral and pharyngeal soft tissues.

Most cats present with reduced appetite or issues with eating or swallowing food. Grooming may be reduced and cats may appear unkempt. Weight loss may be present. Owners may detect an odour from the mouth.

As well as a full clinical examination, blood sampling for routine haematology and biochemistry, along with testing for feline calicivirus, feline herpesvirus and retroviral infection is recommended.

Management of FCGS

Full dental radiographs are recommended with dental cleaning. Removal of plaque and subsequent home cleaning can reduce or eliminate inflammation of the oral tissue. Some cats will respond well to this alone and others will respond poorly. Teeth affected by periodontal disease should be extracted correctly.

Antibiotics can be useful to control inflammation, using agents with both aerobic and anaerobic penetration. Clindamycin (11mg/kg PO q24h) is commonly used. Oral cleansing with a suitable chlorhexidine solution once or twice daily is important to prevent plaque in the short and long term.

It is recommended to reassess patients two weeks after initial dental cleaning. If dental cleaning is not sufficient and clinical signs persist, all molars and premolars should be extracted as soon as possible. Multiple studies have indicated that this either resolves the disorder or reduces inflammation markedly. Total mouth extraction is sometimes required.

Analgesics such as NSAIDs and transmucosal buprenorphine are commonly used in management of these patients at home. Methadone should be used during dental procedures, along with local anaesthesia techniques. Immunomodulatory therapy, for example, interferon, has also been described.

References

Dugdale, A. (2000) Veterinary Anaesthesia Principles to Practice. Oxford: Blackwell Publishing.

Epstein, M.E. (2020) Feline neuropathic pain. Veterinary clinics of North America, 50, pp. 789-809.

Evangelista, M.C. et al (2020) Clinical applicability of the Feline Grimace Scale: real-time versus image scoring and the influence of sedation and surgery. PeerJ 8:e8967 available: https://doi.org/10.7717/peerj.8967 [accessed February 4, 2021].

Monteiro, B.P. et al (2019) Long-term use of non-steroidal anti-inflammatory drugs in cats with chronic kidney disease: from controversy to optimism’. Journal of Small Animal Practice, 60, pp. 459-462.

Monteiro, B.P. and Steagall, P.V. (2019) Chronic pain in cats: Recent advances in clinical assessment. Journal of Feline Medicine and Surgery, 21, pp. 601-614.

Monteiro, B.P. (2020) Feline chronic pain and osteoarthritis’. Veterinary clinics of North America, 50, pp.769-788.

Ramsey, I. (2014) BSAVA Small Animal Formulary. Gloucester: BSAVA.

Reid, J. et al (2013) Pain assessment in companion animals: an update’. In Practice, 39, pp. 446-451.

Sparkes, A.H. et al (2010) ISFM and AAFP consensus guidelines: Long-term use of NSAIDs in cats. Journal of Feline Medicine and Surgery, 12, pp. 521-538.

Zoetis (2022) Solensia: the first and only antibody therapy for feline osteoarthritis pain [available at] https://www2.zoetis.ie/products-and-solutions/cats/oa-pain/solensia?utm_source=Solensia_Homepage_Banner&utm_medium=Banner&utm_campaign=Solensia_Homepage_Banner&utm_id=Zoetis+IE [accessed November 23, 2022].