For me, the last month has really centered around the exploration of pain in our equine patients. In this incredible companion and athlete we are continually challenged not only to recognize pain – especially when the signs are subtle – but to quantify and record the pain that a horse is experiencing.
The first hurdle is that pain is both sensory and emotional (Merskey & Bogduk, 1994). These two aspects need to be considered both separately and together, as we saw in our previous blog, where I looked at the relationship between pain and stress. Stress influences pain, and vice versa (Wagner, 2010).
The second hurdle is that the pain experience occurs as a result of real or potential tissue damage (Merskey & Bogduk,1994). Wow. How do we assess potential tissue damage? How do we quantify a horse’s experience of pain? Well, we could start by looking at some of the parameters that have been linked to pain through research.
- An increase in heart rate and respiratory rate are easy to measure, record and quantify. However, these values are non-specific and are of very little use on their own.
- Circulating levels of cortisol, catecholamines and B-endorphins can be indicative of pain – but can also be an indication of high levels of stress. Again, these are of little value when taken on their own, and furthermore obtaining these measurements is not practical for the majority of us in the field.
- Pro-inflammatory mediators like prostaglandin E2, substance P and bradykinin can indicate an inflammatory response, but again carry the restriction of being non-specific. These measurements cannot quantify the level of pain experienced and they are not available for us in the field.
- Changes in behavior, including elements of demeanor, posture, gait, and interactive behavior, whether subtle or overt, can be an accurate indicator of the presence, severity and location of pain. They may even give us indications of the chronicity of pain. Sounds like a winner to me, but the drawback is that assessing changes in behavior means you need a pre-pain behavior assessment, as well as a great deal of time to get a handle on the full extent of behavioral changes.
These parameters don’t seem all that useful when we look at them like this, but the investigations into these parameters have led to something that is useful – the development of various pain scales.
For a pain scoring system – or really a scale of any kind – to be of value to practitioners, it needs to be easy to use and relevant, the parameters need to be well defined and allow for repeated quick assessment by different observers with consistent results, it needs to be sensitive to different degrees of pain and specific to the kind of pain being assessed. That is quite a tall order.
These are some of the scales that are often used, and which may be of value to you:
- Visual Analogue Scales are a simple horizontal line, representing pain from none to the worst imaginable pain (we have all seen these in a doctor’s office or hospital). These are easy to use, but reliability and objectivity is questionable, becoming more unreliable towards the middle and lower spectrum of the pain scale (Grauw & Loon, 2016).
- Simple Descriptive Scales consist of pre-defined classes of pain to which numbers are allocated, as we see in our lameness grading systems (Grauw & Loon, 2016).
- Numerical Rating Scales are a horizontal line with pre-set numbers from 0-10 at equal distances. An observer circles the number they feel is representative of the level of pain perceived (Grauw & Loon, 2016).
- Time Budget Scales look at behavior over a period of time, allocating a time allowance for certain, specified activities. Due to the need for cameras and the time spent monitoring the animals, this is usually reserved for research settings (Grauw & Loon, 2016).
- Composite Pain Scales look at several pain-related parameters, including behavioral, emotional and physiological parameters, which are scored individually and then added together to provide an overall pain score (Grauw & Loon, 2016).
- Horse Grimace Scales focus on various facial features that are an accurate indication of pain, allocating a point from 0-2 for each feature, and adding up to a total pain score.
If you are a fan of Dr Kenneth Joubert’s lectures, you will know that he is a big advocate of using pain scales in clinic, during assessments and during follow-up assessments, regularly. The scales allow him to create graphs that monitor the patient’s level of pain and response to treatment over a period of time. The use of scales also allows one to show an owner clearly and visibly the change that has occurred over time with interventions. Even the simplest visual analogue scale filled in by an owner on a weekly basis can provide value when looked at over time.
In canine hospital settings, pain scales are rather common. In equine hospitals, they may be used post-operatively to monitor pain, and are often used in conditions like laminitis and colic, for which specific scales have been developed. I think we could incorporate these into equine rehabilitation, too. These can even be a way for us to communicate with owners when they cannot be present at a consult. Owners could fill in a simple pain scale before a consult, or after a consult, giving us feedback in a quick and repeatable manner, and in a way that is slightly more objective than just asking them how the horse is doing!
I have included the above scales as a download for you to print, if you would like to use them in your practice. Please let me know your thoughts and experiences using pain-scoring scales, and if you have not done so before, let me know why not and if you are going to give them a try now 😉
In this blog, I have referred to the research article: De Grauw, J.C. and Van Loon, J.P.A.M. Systematic pain assessment in horses, The Veterinary Journal 209 (2016) 14–22.
THESE TWO FREE PDFs ON PAIN SCALES
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