By: Amanda Pacheco e Yuri Caetano
The animals' inability to verbalise pain makes the diagnostic a quite major challenge. This factor has been suggested as an important cause of analgesic undertreatment in cats and makes the species more likely to suffer pain, bringing sensory-discriminatory consequences, affective-motivational, cognitive-evaluative and also physiological.
How to recognise pain in cats?
Acute pain is the result of a traumatic, surgical, pathological or infectious experience. Pain recognition had based on physiological and behavioural factors. However, physiological changes such as respiratory and heart rate, dilation of pupil, and neuroendocrine tests, such as measurement of cortisol, glucose and beta-endorphins, are poorly correlated with acute pain for the species, since these are changes easily come from stress response, fear and anxiety caused by the environment and hospital management.
Currently, there is a consensus in veterinary medicine the most effective method for recognising and assessing pain in animals should not be based on physiological signs, but rather on behavioural changes, through facial expressions (squinted eyes, tense muzzle, head down), activity (reduced activity, loss of appetite, prostration, hiding, vocalising, excessive licking, aggression - severe pain usually shows depression) and dysphoria (struggling, restlessness and continuous movement can be signs of severe pain). Therefore, pain assessment should be considered as a “fourth vital sign” after temperature, pulse and breathing.
Can we quantify pain in cats?
Nowadays, several studies about recognising pain in cats have been published, mainly focused on building and validating species-specific scales, and also pointing out the limitations that could affect this recognition. These scales should be objective and easy to apply by professionals of all levels (veterinarians, technicians, nurses, and students). The main pain scales to apply in cats are:
- UNESP-Botucatu Multidimensional Composite Pain Scale : It is the first validated scale for cats, reliable and focused on the sensory-discriminative and affective-motivational dimensions of pain. It is considered a highly time-consuming scale, composed of carefully described topics. The interesting thing about it is possible to watch online training videos.
- Glasgow Feline Composite Measure Pain Scale: CMPS - Feline : This validated scale is easier to apply, requiring less time than the former one. It can be applied for any kind of acute pain.
- Feline Grimace Scale: One of the newest pain scales for cats, it is based only on the grimace expressions. It is quite easy to apply by owners, as it is easy and intuitive. It is based on evaluating the position of the ears, whiskers, eyes, muzzles, and positioning of the head in relation to the shoulder.
- Colorado State University - Feline Acute Pain Scale: This scale is based on a questionnaire, assessing the spontaneous and evoked behaviours, as well as interactions between the observer and the cat. It is a scale of easy and intuitive applicability.
There are other scales developed for clinical use, such as the the Visual Analogue Scale, also known as VAS, composed of 10 cm straight line, with no numbers, in which the observer can score from “no pain” to "worse pain"; the Numerical Scale, which is composed similar to the VAS, but with scores from 0 to 10 regarding different behaviours and the University of Melbourne Pain Scale - UMPS.
Despite addressing different parameters, some scales, like VAS and Numerical Rating Scale, are not specific for cats and/or have no validity, reliability and responsiveness. Thus, they could not be useful on clinical conditions since misconceptions can happen and then, failed to help the correct pain management.
How important is pain recognition?
Although the pain assessment by vets is highly important, it is crucial that the owner also knows how to recognise it because they are the main person to understand the usual pet behaviour. So, cat pain management could be started as soon as possible.
Besides the scales aforementioned, we also have guidelines available by the International Veterinary Academy of Pain Management (IVAPM), which are practical and easily applied, mainly focused on the owners, so that they can recognise nontypical behaviours in their pets.
In summary, although it is a great challenge to identify acute pain in cats, we currently have several tools that make easy this task, both for vets and owners. Furthermore, pain must be recognised and treated as soon as possible, and maybe specific for each individual, looking for a maximum effectiveness result for each situation.
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– Evangelista MC et al. Facial expressions of pain in cats: the development and validation of a Feline Grimace Scale. Scientific Reports, 9:19128, 2019.
– Glasgow Feline Composite Measure Pain Scale, 2015.
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