Managing Canine Pain

In its 2001 Guidelines on Complementary and Alternative Veterinary Medicine (CAVM) in 2001, AVMA states "... all veterinary medicine, including CAVM, should be held to the same standards. Claims for safety and effectiveness ultimately should be proven by the scientific method. Circumstances commonly require that veterinarians extrapolate information when formulating a course of therapy. Veterinarians should exercise caution in such circumstances. Practices and philosophies that are ineffective or unsafe should be discarded." The AVMA reminds veterinarians that "State statutes define and regulate the practice of veterinary medicine including many aspects of CAVM. These guidelines support the requisite interaction described in the definition of the veterinarian-client-patient relationship. Accordingly, a veterinarian should examine an animal and establish a preliminary diagnosis before any treatment is initiated... Diagnosis should be based on sound, accepted principles of veterinary medicine. Proven treatment methods should be discussed with the owner or authorized agent when presenting the treatment options available. Informed consent should be obtained prior to initiating any treatment, including CAVM." (20)

Managing Canine Osteoarthritis Pain There are several diagnostic tools available to veterinarians who suspect a dog has osteoarthritis. An orthopedic exam can confirm the presence of joint pain, swelling, and tenderness. Radiographic results generally enable the veterinarian to diagnose OA. Occasionally CT (computed tomography) scanning or MRI (magnetic resonance imaging) may be used, but these are costly and seldom necessary. In some instances, contrast radiographs or so-called stress view radiographs or bone scans may be required. Force plate technology, typically a research tool, may be used utilized to help assess the degree of lameness. The veterinarian may also aspirate joint fluid (arthrocentesis) to rule out inflammatory (e.g., rheumatoid or infectious) arthritis. (21) Although research is underway to identify treatments that may have the potential to stop or repair the pathologic (disease) process involved in canine OA, the disease cannot be cured (22). Dog owners whose pets show signs of osteoarthritis turn to the veterinarian for a treatment plan that not only helps control pain, but also improves joint function and slows the degenerative process within the joint (23). OA-management strategies can encompass weight and diet control, modified exercise, physical therapy, anti-inflammatory and analgesic drugs, and disease-modifying osteoarthritis agents (24). When used as recommended by the veterinarian, these strategies can provide comfort and an acceptable level of function in osteoarthritic animals (25).

• Appropriate nutrition and weight control. It is estimated that up to 40% of the pets in the US are overweight (26). While the veterinary community has not reached consensus regarding whether or not obesity causes OA, there is agreement that it contributes to OA. Therefore, it is important that dogs maintain their ideal weight (24). Correct nutrition in young dogs may lower the incidence of orthopedic diseases such as osteochondrosis, thereby reducing the potential for development of secondary osteoarthritis. Dog owners should refrain from overfeeding young dogs and should avoid over-supplementation with calcium and protein. Research is ongoing to assess the relationship between Omega fatty acids and inflammation in dogs. Omega-3 polyunsaturated fatty acids may decrease production of certain prostaglandins and help reduce inflammation, while omega-6 fatty acids can increase inflammation (23).

• Exercise and physical therapy. Moderate, monitored physical activity can help control clinical signs in dogs with arthritis by helping to prevent obesity and maintain muscle mass; improve strength and range of motion; and reduce the need for the use of analgesics (23). Hydrotherapy can help improve range of motion without exerting stress or strain on the joints.

• Nonsteroidal anti-inflammatories (NSAIDs) help reduce joint pain, decrease synovitis, and improve lameness. Certain NSAIDs are not recommended or approved for use in dogs. These include ibuprofen, meclofenamic acid, naproxen, piroxicam, and phenylbutazone (23).

• Disease-modifying osteoarthritis agents may have a positive effect on slowing the progression of cartilage degradation and promoting cartilage matrix synthesis. While anecdotal information, clinical trials, and research studies indicate disease-modifying agents may be beneficial in treating osteoarthritis, not all patients show a significant clinical response. Therefore, further research is needed to ascertain the effectiveness of this group of products (23). Many oral products in this group contain glucosamine and chondroitin sulfate. See the sidebar Glucosamine and Chondroitin Sulfate for OA: The "Jury" Is Out. Oral products are sold as nutritional supplements and have not been scrutinized fully by the FDA. Injectable agents include polysulfated glycosaminoglycan (PSGAGs) and non-sulfated glycosaminoglycan, though the latter is not commonly used (23).

• Surgical fusion (arthrodesis) may be indicated in severe cases of osteoarthritis or in OA that does not respond to a medication-based treatment program.

Glucosamine and Condroitin Sulfate for OA: The "Jury" Is Out (27) In a published study, researchers from Michigan State University College of Veterinary Medicine reviewed published information on the mechanism of action, pharmacokinetics, clinical efficacy, and safety of glucosamine and chondroitin sulfate. They concluded that "the beneficial effects of glucosamine and chondroitin sulfate, alone and in combination, have been established in vitro in several species. Although concentrations used in recent studies more closely resemble concentrations achievable in vivo after oral administration, cartilage and synovial fluid concentrations have not been determined. As the use of products containing these compounds continues to gain popularity, studies to further elucidate the mechanisms of action and pharmacokinetics are needed. These compounds have promise in terms of protection of articular cartilage and provision of relief of clinical signs of osteoarthritis. Extrapolation of results of human trials to veterinary patients suggests that the use of these compounds is likely to be of greater benefits in patients with mild to moderate osteoarthritis than those with more severe or chronic lesions. "

Managing Cancer Pain The World Health Organization WHO guidelines for the treatment of cancer pain in humans can be used as a rule of thumb for cancer pain management in companion animals (2). See Figure 4. Figure 4: WHO cancer pain management-ladder The non-profit Veterinary Cancer Society (www.vetcancersociety.org) was formed in 1974 by veterinary oncologists. VCS' membership includes specialists in medical, surgical, and radiation oncology, internists, pathologists, pharmacologists, and general practitioners from all over the world. The goals of VCS are:

• To help maintain the highest standards of diagnosis, treatment and prevention of cancer in animals.

• To promote communication among those engaged and interested in naturally occurring and experimental neoplastic diseases of animals with emphasis on domestic animals.

• To provide a means to collect, elucidate, and disseminate relevant data concerning neoplastic diseases of animals and to make them available to veterinary students, practitioners, other interested scientific groups and the public.

• To advise in designing, implementing and evaluating studies of neoplastic diseases in animals.

These goals are being met by the dissemination of a quarterly newsletter, continuing education programs at national meetings, a yearly scientific meeting for members and cooperative therapeutic trials. (28) There is also a Veterinary Technician Cancer Society. Its mission is to be an advocate of the cancer patient and maintain the highest standards of care and treatment of animals with cancer via promoting technician communication, education, and specialization in the field of veterinary oncology (www.vetcancersociety.org/index.php?c=15). (28) A discussion of specific management strategies for cancer pain in dogs is outside the scope of this course.

Managing Otitis Media Pain Tranquilli et al (2) note oral NSAIDs may provide relief from pain associated with the irritation and inflammation of otitis and advise that animals that have undergone surgical removal of auricular tissue in an attempt to treat otitis often display intense distress following surgery. Therefore, there can be acute and chronic components to pain related to otitis media.

Course Wrap-Up Thank you for enrolling in Overview of Chronic Canine Pain. As we have learned, there are a number of conditions that can be expected to produce chronic pain in dogs. We've also seen that diagnosing, assessing, and managing this type of pain can present a tremendous challenge to the veterinary practice team. Furthermore, although there is agreement about the utility of some types of pain-management tools, there is debate about the value of others, and more research is needed in this area. However, thanks to the acknowledgement that animals do experience pain, the contributions of researchers and other leaders in the animal-pain-management field, and the availability of pain-management resources and training materials, pain management is becoming mainstream in companion animal practice. We hope this course has helped you increase your knowledge of chronic pain in dogs, and that it will encourage you to explore companion animal pain management further. Please see the section entitled Action Steps for ideas about how to implement what you've learned.