Sam Gilbert, VMD

Most veterinarians have encountered the 12-year-old canine patient who shuffles into the exam room wagging his tail but growls and snaps as soon as a hand is placed over his hind end. We’re also familiar with the 16-year-old feline patient who is calmly purring one instant only to shriek and hiss at the lightest touch around her shoulder.

While a core objective for veterinarians is to alleviate pain and suffering in their patients, the detection and management of pain can be quite complex. As knowledge of the science underlying pain continues to grow, it has become clear that many of our veterinary patients experience a mixed state of acute and chronic – or more accurately, adaptive and maladaptive – pain and that veterinarians must in turn adapt examination protocols in order to reduce fear, anxiety, stress, and discomfort in painful pets.

Ongoing research has continued to clarify the interplay of adaptive and maladaptive pain in osteoarthritis (OA). Specifically, the effects of the proinflammatory mediator Nerve Growth Factor (NGF) in OA pain create a mixed state of adaptive and maladaptive pain¹.

Adaptive pain is acute and prevents an animal (or a human) from doing something harmful; an example is touching a hot stove, which triggers a reflex response so that the animal quickly withdraws from the source of pain and can start to heal. Maladaptive pain, on the other hand, is chronic and has no clear biological value. When the source of pain is ongoing – such as in OA – NGF and other pain mediators are constantly bombarding neurons in the periphery, which in turn amplifies peripheral and central pain sensitivity and creates a sustained, pronociceptive neural environment¹.

At an early stage, maladaptive pain can result in reduced mobility and an unwillingness to jump or climb. At a late stage, patients can experience pain that is exaggerated, prolonged, and can even be induced by contact far from the site of injury² making patients reactive to being picked up or touched anywhere on their body.

It is critically important for veterinarians to engage with pet owners prior to a physical examination to identify if their pet has shown any signs of maladaptive pain. OA checklists (canine, feline) are easy for pet owners to complete and help them identify physical and behavioral signs of OA in their pets at home. If maladaptive pain is suspected, the veterinarian can then work with the owner and veterinary staff to prepare for the visit and physical exam. Pre-visit analgesia should be recommended, in combination with an anxiolytic if appropriate, keeping in mind daily dosing times of any current OA medications such as non-steroidal anti-inflammatory drugs (NSAIDs) like Rimadyl^® (carprofen) for dogs.

When the patient is in the clinic, staff should use a considerate approach that minimizes restraint and physical manipulation while maximizing comfort and positive reinforcement. Feline examinations can be particularly challenging and expert-guided video demonstrations are available to assist veterinarians.

Once a pet has been diagnosed with OA pain, thorough client education is essential. Veterinarians can utilize the Chronic Pain Teaching Aid to drive discussion with the pet owner about the types of pain and the importance of effective lifelong management. Veterinarians should emphasize adherence to appropriate analgesic protocols and continuous monitoring of pets for plateauing or worsening signs of pain. When untreated, maladaptive pain evolves into its own disease state and affects a pet’s physical and emotional wellbeing; veterinarians and pet owners must work closely together to maintain pets’ long-term comfort. The new scientific understanding of OA pain will help push forward therapies that help veterinarians relieve pets’ pain and improve their quality of life.

IMPORTANT SAFETY INFORMATION FOR RIMADYL: As a class, NSAIDs may be associated with gastrointestinal, kidney and liver side effects. These are usually mild but may be serious. Pet owners should discontinue therapy and contact their veterinarian immediately if side effects occur. Evaluation for pre-existing conditions and regular monitoring are recommended for pets on any medication, including Rimadyl. Use with other NSAIDs or corticosteroids should be avoided.

See full Prescribing Information at https://www.zoetisus.com/products/pages/rimadyldvm/docs/Rimadyl_Injectable_pi.pdf.

References

1. Enomoto, M., Mantyh, PW., Murrell, J., Innes, JF., Lascelles, BDX. (2019) Anti-nerve growth factor monoclonal antibodies for the control of pain in dogs and cats. Veterinary Record 184, 23.
2. Malfait, A-M., Miller, RE., Block, JA. (2020) Targeting neurotrophic factors: Novel approaches to musculoskeletal pain. Pharmacology & Therapeutics 211.

This article was reviewed/edited by board-certified veterinary behaviorist Dr. Kenneth Martin and/or veterinary technician specialist in behavior Debbie Martin, LVT.