“To close your eyes will not ease another’s pain.”
Using Reliable Pain Indicators for Managing Pain in Companion Animals.
What is Pain?
Pain is a sensory experience that warns an animal of an aversive event that may lead to threat or damage to its body. Animals respond both behaviourally and physiologically to pain, in order to prevent or reduce tissue damage and encourage healing. When pain is experienced, animals learn quickly to avoid dangerous or threatening situations, minimising future risk. The extent of behavioural and physiological changes depends on the level of pain, the tolerance and temperament of the animal, and the situation under which the pain occurs, as well as a variety of other factors. Animals may experience pain in several circumstances such as accidental injury, surgery and disease.
In humans, pain is what the patient says it is, and we know that subjective experience of pain varies from individual to individual and doesn’t necessarily correlate with the size or seriousness of the wound or illness. For animals, pain is what we say it is, and this could lead to the real possibility of there being a wide variation in pain assessment and in pain management, with questions regarding the efficacy of analgesia (pain relief) provision. It has been previously suggested that pain management for cats may have been under-provisioned, with a number of studies suggesting that cats could potentially be under treated for pain as compared with their canine counterparts undergoing similar procedures. When surveyed it is interesting to note that veterinarians do not always agree on the need for analgesia in relation to certain conditions or treatments, the amount of analgesia, nor the length of time needed for analgesia.
Indicators of Pain in Animals
There is an old Chinese proverb that goes ’to close your eyes will not ease another’s pain’. The assessment of pain severity is problematic, even in humans, due to its inherently subjective nature. Human pain has both physiological and emotional components, the latter of which is challenging to measure. We know that one person’s experience of pain may be entirely different from another person’s. In non-verbal animals the situation is even more difficult. They can’t tell us how painful they are, where the pain is and how they feel. It’s for this reason that there are likely to be differences in animal pain recognition and management that impact negatively on an animal’s well-being.
It has been suggested that under-provision of analgesia arises because of difficulties in detecting and recognising pain behaviour in some animal species and a lack of agreement regarding the most reliable indicators of a painful state that should be used for assessing pain. Because appropriate pain management relies on accurate recognition of pain, it is essential for the results of research identifying reliable and accessible indicators of a painful experience, to be properly disseminated and applied in practice. Recent laboratory animal research has focused on identifying and validating a range of behavioural indicators including subtle body twitches, changes in willingness to interact with other animals or humans, and specific changes in facial expression. This systematic approach to characterizing pain behaviours, postures and facial expression has now been applied to a range of companion and production animals.
Over the past few years, we have learned a great deal from studies of painful states in animals, resulting in the development of pain scales, ‘grimace’ scores and other such pain measurement tools. These tools are available for all of us to use – and can be helpful when we are unsure about how our pets are feeling. See for example the Equine Grimace App - https://awin-project-hgs.en.aptoide.com/app or the Feline Grimace Scale https://www.felinegrimacescale.com
Behavioural responses to pain can involve the emergence of abnormal behaviours and/or changes in the frequency, duration or circumstances of ‘normal’ behaviour. Obvious behavioural changes such as limping, changes in activity level, guarding a body part and/or over-attending to a body part (eg: licking), are relatively easy to spot – but some species are less demonstrative and so missing the signs of pain can be a risk. Behavioural pain responses are highly species-specific and depend on the evolutionary history of the animal. For example, domestic dogs evolved as predatory pack animals, and on experiencing a painful event the dog may cry out. This response may serve to warn other animals in the pack of the danger and possibly elicit help or attention from group members. Although the horse also lives as a social group animal, it’s a prey species. If the horse was to show similar obvious behavioural responses to painful stimuli to that of the dog it may quickly be picked off as a weak individual or easy target for predators. Therefore, horses are more likely to mask, or hide their pain as a survival strategy, which can make pain detection difficult. Similarly, cats can also be at risk of being under treated for pain because they will often respond by reducing their activity and hiding when in pain. It’s therefore important that changes in an animal’s posture, activity levels and overall behaviour are noticed early, and veterinary advice sought where such changes persist and/or worsen.
In addition to postural and behavioural changes, pain will also impact on an animal’s mental state, altering mood state, demeanour and even temperament. Often responses to pain are quite subtle and may only be seen as slight changes in demeanour, with animals appearing ‘a bit off’ – but they can become ‘depressed’, ‘anxious’ or unresponsive. A normally placid animal may respond aggressively if normal handling becomes painful, and injured animals may act aggressively to prevent a handler inflicting more pain or causing more damage to a specific area of the body. Painful animals may also become less responsive to owners or other animals and will generally have little interest in their surroundings, interaction and other resources such as food. In situations where an animal cannot cope with the duration or severity of pain, a state of ‘learned helplessness’, or apathy, may occur. In this state, the animal ceases most behaviours and may be totally inactive and un-interested in the surrounding environment.
Pain is a Welfare Issue
Untreated or ‘under’ treated pain is obviously a welfare concern. As yet there is no single indicator that can be used to precisely measure an animal’s individual experience of pain. It’s for this reason that a combination of behavioural and physiological indicators are used to provide a more accurate picture of how the animal is feeling, in order to help address and alleviate any pain. Failure to recognise animal pain, or worse, to respond appropriately and swiftly to alleviate an animal’s pain, causes avoidable suffering. For pets to live a Good Life, animal guardians (owners) need to learn about the different species-specific responses to pain, to enable them to more accurately assess how their animal is feeling. Further information about pain behaviours in dogs, cats, horses and rabbits can be found below:
Dogs: https://www.aaha.org/globalassets/02-guidelines/pain-management/painmanagement_dogs_web.pdf
Cats: https://icatcare.org/app/uploads/2022/02/Cat-Carer-Guide_Acute-pain.pdf
Horses: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7931104
Rabbits: https://www.bristol.ac.uk/vet-school/research/projects/bristol-rabbit-pain-scale