Assessing pain in pets

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The landscape of pain management is evolving. Our approach has moved from reactive to more appropriately proactive. A better understanding of the implications of undermanaged pain has led us to develop new tools to aid in the recognition of pain. This has led to new modalities and treatment options we can employ to improve the quality of life for our patients. Pain is the fourth vital sign after temperature, pulse, and respiration.

Acute pain often has a known cause and may be easier to detect, adaptive in nature, and short-lived. Acute pain is present after surgery or injury and is accompanied by inflammation and tissue damage.¹ It can be intense, and behavioral signs can be detected using traditional pain scales. Treatment modalities for the control of acute pain have an end point. Acute visceral pain is
not always detectable with palpation and should be evaluated using clinical signs such as nausea and lethargy.²

Chronic pain is often associated with slow and gradual changes in behavior and mobility. It shouldn’t be characterized by its duration but by the changes that occur in the central nervous system in response to continued stimuli. Chronic pain can lead to maladaptive pain which has no protective purpose and can be difficult to effectively manage. Chronic pain can lead to abnormal pain states such as hyperesthesia and allodynia. This is a result of central sensitization where the nervous system is in a persistent state of high reactivity.³ The swift detection of pain and the quick implementation of treatment can prevent the development of maladaptive pain and improve quality of life.

Acute and chronic pain require different methodologies to assess and manage, with different approaches for cats and dogs. Clinicians should consider the underlying cause of pain and whether it is acute or chronic and match the degree of pain to the doses of analgesics and adjunctive medications.^2,3

Assessing acute pain

Greater tissue trauma, more dissection, longer procedures, preexisting inflammation, or infection are all associated with higher degrees of acute pain and should be managed appropriately.⁴ Acute pain can be assessed using species-specific metrology instruments or pain scales. It is ideal to use validated scales as opposed to scales that have not been proven to be accurate.² Many pain scales share similarities in their approach and features, so it becomes the choice of the hospital to determine which ones fit best into their workflow and culture. Assessment tools should possess certain characteristics, distinguish between the presence or absence of pain, and provide an intervention point for when it is necessary to administer additional analgesics.⁵ Tools should also evaluate the sensory, emotional, and physiologic aspects of pain through observation of behaviors and response to palpation. They should require minimal intraobserver and interobserver variability and be easy to implement and understand.⁶

Cats are midlevel predators exhibiting both predatory and prey-like behaviors. They may not openly express discomfort, but subtle changes can be appreciated if one knows what to look for. Cats depend on their ability to jump and climb as a means of escaping danger.¹ When they can no longer perform these behaviors because of pain, their sociability and mood can change. Some cats will hide whereas others will become aggressive or attempt to flee.⁷ Common signs of acute pain in cats include orbital tightening, flattened ear positioning, muzzle flattening, freezing, not resting in a normal position, hiding, attempting to flee, and aggression.^7,8

As in cats, acute pain that occurs in dogs may be a result of surgery, trauma, infection, or inflammatory disease and can be present in medical conditions. Assessment of acute pain in dogs is generally easier than it is for cats and prey species because we are more familiar with their behaviors. A few common signs of acute pain in dogs include panting, abnormal body positioning, flattened ear positioning, anxious eyes, hiding/refusing to interact, lack of interest in surroundings, reluctance to move, and aggression.²

Multidimensional acute pain scales take a complete look at the pain experience vs subjective observation or the use of a unidimensional scale (eg, visual analog scale, simple descriptive scale). They provide a more accurate assessment with enhanced reliability and less observer bias. Multidimensional pain scales incorporate behavioral observation, palpation, and assessment of the emotional and sensory aspects of pain.

• The Colorado State University Feline Acute Pain Scale is an easy-to-use, description-based scale that evaluate the psychologic and sensory aspects of pain. It covers observation of behaviors, assessment of body tension, and response to palpation. The scale also suggests the importance of facial expression and body position with the addition of illustrations. It has moderate to good interobserver reliability and offers suggestions for when to reassess the analgesic plan.⁶
• The Glasgow Composite Measure Pain Scale is easy to use and designed so that observers couple clinical observations with interactions. The current version includes facial expression illustrations that evaluate ear position, orbital tightening, and muzzle shape in cats. This scale is validated with good interobserver reliability and can be used to assess pain from a variety of sources including postoperative, trauma, and medical cases. Minimal training is required for its use, and it can easily be implemented in a busy hospital. However, it can be difficult to use in cats who resent interaction.^4,9
• The Feline Grimace Scale looks at facial expression and body positions that are known characteristics of pain in cats including ear position, orbital tightening, muzzle tension, whisker position, and head position. Training materials can be downloaded from the Feline Grimace Scale website, and a free smartphone app is available.⁸
• PainTrace is a small device that connects to the axillary region via noninvasive sensors such as an electrocardiographic patch. It taps into the nervous system, picking up on direct biosignals in the pain matrix. The signal is transmitted via Bluetooth to an iPad where a graph is displayed. The baseline of the graph represents the presence or absence of chronic pain, and negative deflections (deltas) during manipulation, palpation, or ambulation detect and quantify acute pain. This device can be used in dogs, cats, and large animals. It has been validated against human self-report, and a variety of studies on its validity in veterinary patients are in prepublication.¹⁰

Assessing chronic pain

For chronic pain, it is important to engage the owner in a discussion of at-home behaviors using checklists designed for evaluating changes in mobility and demeanor. This should occur with a thorough history and physical examination.

Many clients are unaware of the presence of chronic pain. They may assume that their pet is slowing down because they are getting older. Client education and involvement is imperative to identify and appreciate the need for chronic pain management. As with acute pain, chronic pain assessment should begin with the physical exam and include evaluation of behavior, posture, gait, and client reports.^3,11 Utilizing the PainTrace device during an exam can help take some of the guesswork out of pain assessments.¹⁰

As an intermediate species (both predator and prey), cats are difficult to assess for chronic pain. Many cats are terrified in the veterinary hospital and will become tense and freeze. Persuading a cat to ambulate normally to assess gait is nearly impossible. Because of these challenges, we are forced to approach pain assessment in cats from a different angle compared with dogs. Cats need access to vertical spaces to escape danger. If they are unable to jump or climb, they will feel threatened and may become aggressive or display a change in sociability. They may come to resent handling and become less engaged.^5,11

Having owners fill out chronic pain screening forms is essential not only for determining whether chronic pain is present but also educating owners about what to look for in an aging cat. A few common signs of chronic pain in cats include inability or reluctance to jump up or down without an intermediate surface, dull or unkempt haircoat, hind end muscle wasting, decreased appetite, change in sociability, areas of hair loss or thinning hair over specific anatomy, limping, and not using the litter box.^5,11,12

Assessing chronic pain in dogs relies on client reports in addition to dog behavior in the exam room. Body condition scores, mobility, and range of motion are helpful tests to perform in the examination. A dog who limps at home may not limp in the animal hospital, and this can be frustrating for veterinarians and clients. A few common signs of chronic pain in dogs include difficulty rising, loss of stamina, limping, soiling the home, laying down more than standing or sitting, decreased appetite, change in sociability, and licking specific areas of the body.^2,3,13

Assessment tools for chronic pain include the following:

• The Feline Musculoskeletal Pain Index is a screening tool for chronic osteoarthritis (OA) pain in cats. It is a 17-question simple checklist for clients that is designed to evaluate a pet’s mobility, ability to perform daily activities such as litter box use and playing, and interactions with family members and other pets.¹¹
• The Feline Osteoarthritis Checklist was created by Zoetis for clients to complete regarding the mobility, sociability, emotional well-being, and litter box habits of cats. It offers an educational component, images, and animations that make it user friendly.¹⁴ There is a version of the checklist for dogs as well.
• The Canine Brief Pain Inventory (CBPI) allows clients to rate the severity of their dog’s pain and how that pain may interfere with daily life. It was designed to monitor OA and is a valid chronic pain scale in its original form. A CBPI user guide exists to help owners and veterinary professionals implement this tool. It includes an overall assessment of pain and description of function including general activity, enjoyment of life, ability to rise, ability to walk and run, and ability to climb stairs.¹³

Managing pain in pets

Anxiety, fear, and stress can exacerbate pain. Handling all pets, especially those in pain, with patience and respect can make a world of difference. Fear Free certification for individuals and hospitals is a brilliant way to build a solid foundation to improve patient care.^4,9,15 However, one does not need to obtain Fear Free certification to implement the ideas put forth in that program.

Low-stress restraint, handling, and environmental design can go a long way to helping pets and clients feel comfortable. Previsit medications to ease fear, anxiety, and stress are also important for managing pain. Use Fear Free techniques and low-stress handling with previsit anxiolytic medications and discuss the importance of these progressive steps with clients.¹⁵

Effective pain management should include properly conducted pain assessments performed regularly throughout the postoperative period and around the administration of analgesic therapy to assess efficacy. It is important to engage the entire veterinary team and implement a culture that supports pain management. Provide employees with pain-related continuing education and training. Develop or download hospital-specific materials and pain management protocols/guidelines and never make pain management an option for clients to opt into or out of.

Schedule pain-related appointments and consider assigning a team member with special interest in pain management to act as an outreach coordinator to follow up with clients and discuss progress and challenges. Clients need to understand the reasons behind early intervention. Therapy should minimize financial, logistical, physical, and emotional burden placed on caretakers.

Find acute and chronic pain scales for commonly seen species. Train staff on their use and be consistent with their implementation. Facilitate pain-related medication refills, diets, and therapies that will benefit pets with both acute and chronic pain.

Every pet should be evaluated for pain from the moment they walk in the clinic. Reevaluate patients with chronic pain at least every 3 to 6 months; this will help to build strong bonds with clients. Undermanaged pain causes prolonged pain and other consequences that can delay healing and recovery.

Key takeaways

Proper pain management is everyone’s responsibility. By creating a culture that centers the importance of pain recognition and alleviation for both the entire veterinary team and clients, we can move the profession steadily forward in improving the lives of the pets we love and treat. It is better to manage pain that isn’t there than not manage pain that is.

References

1. Merola I, Mills DS. Systematic review of the behavioural assessment of pain in cats. J Feline Med Surg. 2016;18(2):60-76.vdoi:10.1177/1098612X15578725
2. Hernandez-Avalos I, Mota-Rojas D, Mora-Medina P, et al. Review of different methods used for clinical recognition and assessment of pain in dogs and cats.Int J Vet Sci Med. 2019;7(1):43-54. doi:10.1080/23144599.2019.1680044
3. Cimino Brown D, Boston RC, Coyne JC, Farrar JT. Development and psychometric testing of an instrument designed to measure chronic pain in dogs with osteoarthritis. Am J Vet Res. 2007;68(6):631-637. doi:10.2460/ajvr.68.6.631
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6. Shipley H, Guedes A, Graham L, Goudie-DeAngelis E, Wendt-Hornickle E. Preliminary appraisal of the reliability and validity of the Colorado State University Feline Acute Pain Scale. J Feline Med Surg. 2019;21(4):335-339. doi:10.1177/1098612X18777506
7. Moffat K. Addressing canine and feline aggression in the veterinary clinic. Vet Clin North Am Small Anim Pract. 2008;38(5):983-vi. doi:10.1016/j.cvsm.2008.04.007
8. Evangelista MC, Watanabe R, Leung VSY, et al. Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale. Sci Rep. 2019;9(1):19128. doi:10.1038/s41598-019-55693-8
9. Steagall PV, Monteiro BP. Acute pain in cats: recent advances in clinical assessment. J Feline Med Surg. 2019;21(1):25-34. doi:10.1177/1098612X18808103
10. Quantifying pain to lead the path to wellness. PainTrace. Accessed February 17, 2023. http://www.paintrace.com
11. Benito J, Hansen B, Depuy V, et al. Feline musculoskeletal pain index (FMPI): responsiveness and testingofcriterion validity. J Vet Intern Med. 2013;27(3):474-482. doi:10.1111/jvim.12077
12. Tatlock S, Gober M, Williamson N, Arbuckle R. Development and preliminary psychometric evaluation of an owner-completed measure of feline quality of life. Vet J. 2017;228:22-32. doi:10.1016/j.tvjl.2017.10.005
13. Brown DC, Boston R, Coyne JC, Farrar JT. A novel approach to the use of animals in studies of pain: validation of the canine brief paininventory in canine bone cancer. Pain Med. 2009;10(1):133-142. doi:10.1111/j.1526-4637.2008.00513.x
14. Could your cat have osteoarthritis? Zoetis. Accessed February 17, 2023.
    https://www.zoetispetcare.com/checklist/osteoarthritis-checklist-cat
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