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Are Fido and Fluffy in Pain? Unravelling the mystery of pain assessment

Jennifer F. Johnson VMD, CVPP

Every day, veterinarians are faced with this fact; our patients are in pain. The identification and treatment of pain in our patients is key to their longevity and quality of life.

Consequence of Untreated Pain

Studies of pain in humans and animals repeatedly show the significant consequences of unalleviated pain, most notably the increase of mortality in patients suffering from pain. Pain is responsible for a myriad of chemical and neurologic changes which, if untreated, can lead to dire pathophysiologic consequences involving multiple organ systems. The neurohumoral responses to pain and stress trigger a cascade of events, including changes in cortisol, catecholamines, and other hormones. This stress response to injury and subsequent immune system stimulation, precipitates the release of cytokines augmenting the systemic inflammatory response syndrome (SIRS). Unchecked, SIRS will lead to multiple organ dysfunction syndrome. The cause or extent of the pain and trauma to the body is not the issue, what will be the ultimate cause of morbidity and mortality is the body’s response to the disease. It has been said that stress kills. One could better surmise that unalleviated pain, no matter what the cause, is a prime component of patient death.

The Problem

Small animal veterinary practitioners know that individual patients may have vastly different responses to pain, most of the time the clinical observations can be very subtle. This leads most clinicians to use palpation as the primary tool for pain assessment. In cats, palpation assessment can be confounded by potential aggressive behavioral changes in those cats that may or may not be in pain, but resent palpation. An additional issue is the failure of objective evaluation when using pain scales. Common rhetoric states that pets do not have a placebo effect – however the same cannot be said about pet owners, or even caregivers.  In 2012, while collecting data analyzing dogs with osteoarthritis, Michael Conzemius DVM, PhD concluded that a placebo effect in owner evaluations occurred 56.9% of the time, while even more concerning – the placebo effect in veterinary – or caregiver evaluations - occurred between 40-45% of the time. This caregiver placebo effect can be problematic to clinicians as we try first, to identify pain, and then, subsequently try to analyze the success or failure of a particular treatment. Some common reasons for subconscious bias stem from the fear of impending euthanasia, the excuse for euthanasia, and the social desirability related to a particular response. It is only with a well-rounded combination of assessments can veterinary practitioners expect to find meaningful success in patient comfort and pain relief.

Measuring Success in a Clinical Setting

Veterinarians must consider pain measurement in every patient and strive to quantify pain along with other vital signs such as temperature, pulse, and respiration. With continued pain assessment, one can determine the success of treatment in an unbiased and equivalent fashion. In veterinary medicine, we must continue to collect data, we must continue to collect clinical evidence, and we must exercise care to document responses or non-responses to treatment in the most unprejudiced way possible. This is especially important as we continue to develop multimodal pain management protocols which include non-pharmacologic modalities such as tPEMF. Clinical case outcome data is helpful when evaluating the success or failure of nonpharmacologic treatment. With the scarcity of randomized, double-blinded placebo studies specific to veterinary patients, we must do our best to reduce opinion and bias. To this end, it is important to review reasonable ways to document pain management treatment outcomes to carefully quantify the results of any pain management protocol. Lord Kelvin stated, "If you cannot measure it, you cannot improve it”. Using a practice-specific pain scale for evaluation of patients before, during, and after treatment is critical for measuring treatment success. Each validated pain tool and HRQL assessment needs to be used “as-written”, to reduce response bias that occurs so often with client as well as clinician caregiver reporting. There are many published references available to help you design and implement a protocol in your hospital for pain assessment, including subjective, objective, and semi-objective tools. It is helpful to consider implementing a practice-specific pain assessment scale where all veterinarians and nurses are consistent. It may be valuable to consider two distinct pain measurements metrics, one for in-practice use and a second validated tool for client assessment and measurement.

Additionally, new tools are being developed and adopted which help clinicians identify and focus on pain more clearly. The use of veterinary-specific medial thermal imaging is a highly sensitive tool for evaluating physiologic changes, and functions as an adjunct to more specific diagnostic testing. The Pain Trace® is a wearable monitor that measures signals from the nervous system to create a graph, similar to an electroencephalogram (ECG). This biosignal graph can be used to qualify and quantify pain in a patient, as well as document response to treatment.

Education is the Key

If pet owners do not realize the signs of pain, they will not understand the need for treatment. Each year, September is “Animal Pain Awareness Month” and this provides a great opportunity to discuss the suble ways that animals hide pain. The International Veterinary Academy of Pain Management provides excellent client education handouts (www.ivapm.org). Share tools with pet owners, using available educational websites such as painfreecats.org and caninearthritis.org and continue the conversation to educate colleagues, staff and pet owners about how very important it is to recognize and treat animal pain.

• Conzemius MG, Evans RB (2012) Caregiver placebo effect for dogs with lameness from osteoarthritis. JAVMA 241(10):1314-19.
• Evangelista M, Watanabe R, O'Toole E, Pang D, Steagall P (2018). Facial expressions of pain in cats: development of the Feline Grimace Scale. Association of Veterinary Anaesthetists Spring Meeting at St Georges, Grenada March 2018.
• 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.
• Kerwin S. Orthopedic examination in the cat: clinical tips for ruling in/out common musculoskeletal disease. J Feline Med Surg 2012; 1: 6–12.
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• Zieske L, Dullen D, Mohanty M. Comparing veterinary diagnosis and a novel non-invasive devise (Paintrace®) to differentiate location and quantify pain in dogs. Vet Comp Orthop Traumatol 2018; 31(S 02): A1-A25.