What is pain?
The International Association for the Study of Pain (IASP) definition of pain is;
Pain is a complex sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.
Thinking about this statement from another angle it is often said ‘pain is not just about how it feels, it’s how it makes you feel.’
A recent amendment to the IASP definition adds ‘ the inability to communicate in no way negates the possibility that an individual is experiencing pain and is in need of appropriate pain relieving treatment.’
Pain is an individual experience for that person or animal and much of this difference is related to genetics, context, emotion, psychology and physiology. Two dogs undergoing the same surgical procedure cannot be expected to respond the same to the painful stimulus. Pain is always subjective. Make this a golden rule in your pain management.
Robertson (2002) states that the important issues for us as veterinary professionals is to define, assess, prevent and alleviate pain. Further to this Robertson adds that an animal’s inability to anticipate relief from pain also contributes to additional suffering. In people this psychological aspect to the placebo effect can be advantageous but we cannot explain this to the animals under our care.
Latest Guidelines
In 2014 WSAVA convened a Global Pain Council, the product of which was a set of guidelines for recognition, assessment and treatment of pain. These guidelines recognise pain as the 4th vital sign, stating that in the vast majority of cases pain can be recognised and effectively treated. Our experience tells us which conditions are painful and when we can predict pain. We are all very familiar with the concept of pre-emptive analgesia, whereby analgesia is administered prior to the painful stimulus however this has moved on to the term preventive analgesia which you can read about here. Follow this link to the WSAVA guidelines.
Incorporating pain scoring into your practice
Bradbury & Morton (2017) illustrate how we can improve pain management in practice with the use of behavioural science. The article considers all of the stakeholders in the pain piece within the practice, from the pet owner, nurse and receptionist, right through to the vet – who is the one person who has the ability to prescribe the analgesic.
Do colleagues in your practice have the capability, opportunity and motivation to treat pain? If you are training your team on pain recognition, don't forget to add this component in.
Pain Assessment
When considering whether an animal is in pain there is a multitude of information to take into account when deciding the best management strategy for that patient. Unless you look for something, you will never find it, so a simple starting point is that all patients should be evaluated for signs of pain after surgery at appropriate intervals.
There are several pain scales to assess pain in dogs, but often your overall impression and clinical experience also counts. If you consider an animal to be in pain, then that animal should receive analgesia. The patient can then be reassessed at a time frame appropriate to the drug used. It is best to analgese a patient rather than leave them in pain. If the patient improves following analgesia, then the pain hypothesis holds up. On the converse side, if animals are repeatedly medicated with drugs without being in pain, then they may suffer detrimental effects from the drugs.
Composite Pain Scales
These are the acute pain scores that I recommend. The Shortform of the Glasgow Composite Pain Scale (CMPS-SF) was developed using psychometric principles of validity, reliability and responsiveness. Pain scales exist for dogs and cats. Click here to access.
Validity – provides evidence that the instrument is able to measure what is was designed to measure.
Reliability – can the instrument measure accurately and repeatedly what it is intended to measure? Can different observers produce the same or similar results?
Responsiveness – can the pain scale detect small changes in pain state before and after administration of an analgesic?
The CMPS-SF is a behaviour-based, validated pain score for acute pain in dogs. This pain score cannot be used for cats (see cat pain scale below). The total CMPS-SF score has been shown to be a useful indicator of analgesic requirement and the recommended analgesic intervention level is 6/24 or 5/20 for dogs and 4/20 for cats.
Unidimensional pain scales
Although simple to use these are less accurate than the composite scales mentioned above as they do not measure the affective component of the pain.
A visual analogue scale is a measure used widely in humans. The patient is asked to put a mark on the line where they consider their pain to be. The line is a scale from 0-100. Zero indicates no pain at all and 100 represents the worst pain imaginable. The distance from the no pain end to the patient mark is their pain score. This has been validated in cats for intervention and the authors suggest analgesia should be administered at a pain scale of 30/100.
Similar to this is a numerical rating scale which is numbered from 0-10 and the patient marks the number which correlates to their level of pain.
Both scales are very easy to use and can be applied to everyday practice with little extra work. Ideally the same person should score the pain each time to give the best representation of how the patient changes over time. Validation of this scale suggests we should administer analgesia at 4/10.
A simple descriptive scale will have several expressions used to describe pain and the patient has to select the description best fitting their pain. These scales have been used in veterinary studies evaluating analgesia.
The VAS, SDS and NRS are unidimensional scales which have a high tendency for observer influence, hence it is recommended that composite pain scales are used.
Practical Pain Scoring Tips
Pain score using a validated scale
Intervene
Reassess
Record
Rules of pain management
Each patient is individual.
If you think they are painful, provide analgesia.
Treat the pet for as long as they are painful.
With this information you are armed and ready to assess pain. This can be done by any member of the veterinary team and our aim is to work together to alleviate pain in our patients every day.
References
Bradbury, G., & Morton, K. (2017). Using behavioural science to improve pain management. In Practice, 39(7), 255.2–272. http://doi.org/10.1136/inp.j3251
Calvo, G., Holden, E., Reid, J., Scott, E. M., Firth, A., Bell, A., et al. (2014). Development of a behaviour-based measurement tool with defined intervention level for assessing acute pain in cats. Journal of Small Animal Practice, 55(12), 622–629. http://doi.org/10.1111/jsap.12280
Mathews, K., Kronen, P. W., Lascelles, D., Nolan, A., Robertson, S., Steagall, P. V., et al. (2014). Guidelines for recognition, assessment and treatment of pain: WSAVA Global Pain Council members and co-authors of this document:. Journal of Small Animal Practice, 55(6), E10–68. http://doi.org/10.1111/jsap.12200
Morton, C. M., Reid, J., Scott, E. M., & Holton, L. L. (2005). Application of a scaling model to establish and validate an interval level pain scale for assessment of acute pain in dogs. American Journal of ….
Reid, J., Scott, M., Nolan, A., & Wiseman-Orr, L. (2013). Pain assessment in animals. In Practice. http://doi.org/10.1136/inp
Robertson, S. A. (2002). What is pain? Journal of the American Veterinary Medical Association, 221(2), 202–205. http://doi.org/10.1016/j.jacr.2017.01.039