Research roundup
The aim of the research roundup is to provide vet professionals with an easy-to-read digest on items of research in pain management which focus on one common subject area.
This research roundups provide a single point of reference for the reader.
Subject
Models of pain management
Title of the paper
Beyond biopsychosocial: The keystone mechanism theory of pain
Lawn, T et al. (2023) Beyond biopsychosocial: The keystone mechanism theory of pain. Brain, behavior, and immunity 114, 187-192. doi:10.1016/j.bbi.2023.08.018
Summary of the paper
The Keystone Mechanism Theory (Lawn et al 2023) states that pain is a product of multiple interacting systems, with one or more keystone mechanisms playing a pivotal role in each individual's pain experience. This theory borrows its name from the architectural concept of a keystone, the central stone at the summit of an arch that holds the entire structure together. These mechanisms can be biological, such as specific neurotransmitter pathways or inflammatory processes; psychological, such as cognitive biases or emotional states; or environmental, such as social support or exposure to stressors.
One of the core principles of this theory is the notion of "interdependence." The keystone mechanisms are not static but are dynamically influenced by other factors within the pain network. For instance, a person’s psychological state can influence their biological pain mechanisms, and vice versa. This interdependence means that altering one component of the system can have cascading effects on the entire pain experience.
Additionally, this theory suggests that interdisciplinary approaches to pain management—incorporating medical, psychological, and social interventions—are likely to be more successful than treatments that focus on a single aspect of the pain experience. This aligns with the growing emphasis on biopsychosocial models in pain management, which recognize the multifaceted nature of pain and the need for comprehensive treatment strategies.
Another important principle is context-dependence. The effectiveness and influence of a keystone mechanism can vary depending on the context in which pain is experienced. For example, the same biological mechanism might have different impacts on pain perception depending on whether an individual is under stress, well-rested, or experiencing fear. This principle underscores the individualized nature of pain and the necessity for personalized approaches to pain management.
Revisiting current theory
The biopsychosocial model of pain is a comprehensive framework that recognizes the complexity of pain as a multifaceted experience, encompassing biological, psychological, and social dimensions. Unlike traditional models of pain, which primarily focus on physiological aspects, the biopsychosocial model integrates multiple perspectives to understand how pain is experienced, perceived, and managed by individuals. This approach requires us to look at every factor which could contribute to the management of pain, for example the ability of exercise to contribute to overall wellbeing.
In a world where we are all short of time, it’s easy to reach for our quick wins to get us through. In this article we will illustrate these points with reference to osteoarthritis in dogs and cats - and explore how to incorporate a biopsychosocial approach into our OA care plans.
Biological Factors in Pain
The biological aspects of osteoarthritis are probably where we all start with explaining to caregivers what is going on with their pet. The biopsychosocial approach encourages us to consider more than just the biological elements. No doubt it is important to give our clients an understanding of the disease process, and throughout this article we expand on other areas that are equally as important in order to optimally manage OA. Are we better to give a very brief pathophysiological explanation and then check with the client if they would like more information? Do they hear what we say in that consultation or would they prefer us to direct them to further resources. Do we have those resources available on our website or can we recommend another source of information? We know from the literature that clients value our personal recommendations in OA care. The understanding that we are trying to bring to our clients is that there are multiple factors that can contribute to the overall management plan. The analgesics available to us form our prime approach to addressing the biological factors which should be coupled with physical therapy.
Psychological Factors in Pain
Psychological factors play a crucial role in the perception and management of pain and the phrase ‘pain is whatever the patient says it is’ is a good explanation. Emotions, thoughts, and mental health conditions can significantly affect how pain is experienced. Anxiety and depression are commonly associated with chronic pain, often exacerbating the perception of pain and making it more difficult to manage. Similar is true in dogs and this is something that clients will mention to us – one of the behavioural domains in the Vetmetrica Health Related Quality of Life instrument is ‘happy & content’. Also, in the veterinary world we have the caregiver themselves to consider. If that person has taken their dog for a run every day for the last 5 years, and now they can’t do that, this also has a significant influence on that person’s wellbeing. In multi dog households there can be an element of guilt if the exercise ability of one dog affects the walks of the other dog - and the caregiver struggles for time to do two separate walks for both dogs.
The interplay between pain and psychological states results in pain catastrophising and is an area requiring more research. Pain catastrophising is well documented in human pain and leads us to question the influence of the caregiver on how they interpret the pain that their pet is experiencing. We know the placebo effect in cats provided with analgesics is high (Gruen et al 2017) when the outcome measures are reported by the caregiver. Further research is needed on the role of pain catastrophising and how this influences chronic pain scores which are of course all completed by the caregiver.
Social Factors in Pain
Social and environmental factors are also integral to the biopsychosocial model of pain. These include cultural beliefs, social support networks, and socioeconomic status, all of which can influence how pain is perceived, reported, and treated. Social support plays a vital role in coping with pain. Individuals with strong support networks often experience better pain outcomes, as social support can buffer against the negative psychological effects of pain. Resource such as Canine Arthritis Management and International Cat Care help caregivers to feel that they are not alone in caring for a pet with OA and signposting clients to these organisations is recommended.
Variability in pain experiences among different individuals is recognised in pets with chronic pain. An explanation of the biopsychosocial model helps us to understand that and hopefully helps you understand why you may not be seeing the response you expect in managing a particular case.
Key points to aid reflection
It is now clear to the reader that the provision of analgesia to a dog or cat with OA is only one part of managing that pet’s pain. With consideration of all the factors we start to move to a wider approach, although it is clear from the preceding discussion that there are still other factors at play.
It goes without saying that we can’t address all of these factors in one consultation. Taking some time to create an OA management approach as a practice can really help everyone involved. Which aspects of this can be managed in nurse clinics? Are the team all familiar with local rehabilitation practitioners so they are equipped to make recommendations to caregivers?
We now review a case with a blended keystone & biopsychosocial framework and ask you how you would approach this dog.
Gem 7yo MN Golden Retriever hip OA
Current treatment – meloxicam SID for last 2 years.
Caregiver reported outcome measures (CROM) - an increase in lameness and limitation in his usual walk – he turns around to go home at 20 minutes and is less keen for a second walk that day. Less interactive with the family – spends more time in the kitchen when he is comfortable but takes himself to another room when uncomfortable. Pain is worse after longer walks, typically when the teenage kids have taken him out. Sometimes the caregivers forget to give his NSAID and feel guilty about this.
Biologic aspects
It is likely that the OA has progressed and Gem is now in need of additional analgesics. How can we address this analgesic need with the background of variable compliance?
List the analgesic options you would consider now for Gem.
Do you recommend diagnostics?
Psychological
Gem is a key member of the family. The family are sad to see him not interacting with them. The kids want to take him on walks and say that he is always keen at the start of their walks.
The adults in the house experience guilt when they forget to medicate him.
What would you consider to address the psychological aspects of Gem’s management?
Social aspects
The family are in need of support in managing Gem. The teenage kids now see that over-exercise is a factor in Gem’s pain breakthrough. They ask for resources that will help them understand how to manage a dog with OA.
Which resources do you currently share with clients and what other options should you consider?
Going back to The Keystone Mechanism Theory we are reminded that pain is a product of multiple interacting systems, with one or more keystone mechanisms playing a pivotal role in each individual's pain experience - and you can appreciate how these areas illustrated in this case are closely linked.
A wider appreciation of how pain management theory has evolved can help us in several ways. With an improved understanding we can recognise the importance of looking beyond simply prescribing analgesics. This understanding guides the conversation we have with our clients so they also see the value in a holistic approach to OA management. How many times have you heard a client say ‘well the drugs you gave me last time aren’t working’. No-one wants to hear that at the start of a consultation! How will you use your understanding of the biopsychosocial or keystone model to reframe your OA consultations?
In this section you will find our ‘everyone should read this’ recommendation and a review that we have chosen to support your next steps in integrating this with your clinical practice.
Everyone should read this
This short video by Dr Zoe Belshaw entitled ‘The Pet Owner’s Perspective’ is a really useful piece of information, and fits perfectly in the biopsychosocial discussion.
Recommended review article
Pye et al (2022) Advances in the pharmaceutical treatment options for canine osteoarthritis
Reflections
The answers below are suggested – and worked in this case. With limited evidence on analgesics beyond NSAIDs there is often no right or wrong option. What is important is that we have a way to assess the outcome of our chosen option – whether that’s through pain scoring or the use of caregiver reported outcome measures (CROMs).
Biologic aspects
Switch NSAIDs – some NSAIDs are more effective that others although there is little science to this
Replace the daily NSAID with a weekly NSAID (enflicoxib)
Replace NSAID therapy with anti-NGF therapy (bedinvetmab)
Add a second analgesic to address central sensitisation by targeting the NMDA receptor. Options are amantadine, memantine or ketamine subcutaneously. For more details click links.
Outcome
Gem responded really well to weekly enflicoxib combined with memantine 0.5 mg/kg SID. The family programmed their voice assistant to remind them to give his medication. He stopped wanting to turn back on his walks and his exercise management was guided by his physiotherapist.
Psychological options
Start physiotherapy and involve the teenage kids with Gem’s appointments.
Outcome
After optimising Gem’s analgesics, a period of one month was given prior to increasing Gem’s exercise. By working with the physiotherapist the whole family gained a much better understanding of how to ensure Gem was comfortable. The physio exercises ensured the family interacted in Gem’s care and this removed any feelings of guilt that he wasn’t getting the same length of walks he used to.
Social aspects
Outcome
Through working with a local physiotherapist, Gem’s caregivers gained a much better understanding about the pain of OA and key management options. This was supported by resources available on Canine Arthritis Management on exercise control.
A wider appreciation of how pain management theory has evolved can help us in several ways. With an improved understanding we can recognise the importance of looking beyond simply prescribing analgesics. This understanding guides the conversation we have with our clients so they also see the value in a holistic approach to OA management. How many times have you heard a client say ‘well the drugs you gave me last time aren’t working’. No-one wants to hear that at the start of a consultation! How will you use your understanding of the biopsychosocial or keystone model to reframe your OA consultations?
References
Gruen, M E et al. (2017) Caregiver placebo effect in analgesic clinical trials for cats with naturally occurring degenerative joint disease-associated pain. The Veterinary Record 180,19 473 doi:10.1136/vr.104168
Lawn, T et al. (2023) Beyond biopsychosocial: The keystone mechanism theory of pain. Brain, behavior, and immunity 114, 187-192. doi:10.1016/j.bbi.2023.08.018
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