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Practical Acute Pain Assessment

PRACTICAL ACUTE PAIN ASSESSMENT

Why should we assess acute pain?

Assessment of pain is complex and multi-dimensional, and should aim to take into consideration the sensory, emotional and behavioural aspects of pain. Assessing these components can be challenging in our domesticated species, especially in the hospital setting.

Pain scoring is an important and useful tool for monitoring surgical and medical patients during their hospitalisation, as well as to assess efficacy of any administered analgesia. Pain scoring allows for a more objective assessment of a patient’s analgesic requirements, and although not designed to replace the veterinary team’s own assessment, it is an excellent adjunct, allowing for more objective patient evaluation. Pain scoring may also be useful when assessing whether analgesia prescribed to a patient is sufficient and therefore allows for objective reassessment at an appropriate time.

There are a number of validated pain scoring systems available. By validating a pain assessment tool, a developed system will have been evaluated in a test population based on certain physiological and behavioural measures. It is tested to ensure reliability and repeatability when making a patient assessment. It therefore has the ability to detect pain when present and to allow for multiple users to input into repeated patient assessment. Pain scoring systems that have not been validated may fail to pick up on a patient that requires further analgesia and therefore be of limited clinical use. 

Pain assessment tools may be selected for specific requirements within a clinic, and some tools will have been developed to assess acute surgical pain, but may be limited in terms of procedure or body systems. In certain specific settings a validated system may not be available and a modified system may be necessary to assess the patient adequately.

When incorporating pain scoring into practice it is important that the whole team is trained to use the scale selected and instructed in how it will be implemented within the clinical environment. Time should be allowed for patient assessments and clinicians and nurses should be aware of the intervention levels for the scales used. A suitable practice protocol should be in place to treat those patients that score above the intervention level, and importantly when nurses are using pain scoring as part of their daily assessments, protocol should also be in place to allow for a clinician to prescribe analgesia when required. This is particularly important when a patient is assessed to be painful despite an analgesic plan already being in place. Pain scoring is therefore a dynamic process!

Enhanced recovery after surgery
The use of enhanced recovery (ERAS) programmes in human medicine aim to ensure the best possible recovery from surgery and anaesthesia. This is a relatively new area in veterinary medicine, but one that may be explored following the successful introduction of pain assessment. Pain assessment and provision of analgesia form an integral and vital part of this concept. Other components of this concept include; appropriate and goal directed fluid therapy, early feeding and early patient mobilisation. The use of appropriate analgesia plays an important role in ensuring that the other components are also able to be fully addressed. 

Aims of pain assessment

A pain scoring system for use in practice should be selected on a number of key requirements, such as; 
• The species to be assessed, as all scales are species specific
• Ease of use, the easier a scale is to complete the more likely the team is to use it
• The main type of pain to be assessed i.e. post-surgical acute pain or chronic pain
• Time required for patient assessment. Assessments should be performed on a regular basis, which may take into consideration factors such as previous analgesia administered, the type of procedure undertaken and the species

Care should be taken to avoid misinterpretation of factors such as patient temperament and sedation, and if there is ever any doubt about a patient displaying signs consistent with pain, then further analgesia should be administered and the patient reassessed after an appropriate time period. 

Patient benefits
There are many benefits to the patient when introducing pain assessment systems, including reducing unwanted drug effects, such as dysphoria, nausea, gastrointestinal ileus and most importantly improving patient comfort and minimising stress during hospitalisation. Dysphoria is a commonly observed unwanted effect following opioid administration and leads to additional stress during patient hospitalisation. A study assessing dogs following administration of fentanyl during anaesthesia reported an incidence of 23.9% showing signs of dysphoria in the recovery period (Becker et al., 2012) and the incidence of dysphoria following administration of morphine to dogs has been reported to be between 10 and 30% (Lucas et al., 2001; Wolfe et al., 2006).

Improved patient comfort is the goal of good analgesia, including ensuring that stress is kept to a minimum during the hospitalisation period. Inability to show normal behaviours, such as eating, drinking and toileting habits may increase levels of stress and anxiety. Ensuring analgesic dosing is appropriate will reduce the likelihood of nausea and anxiety due to unwanted drug effects.

Unwanted effects may be seen with some analgesic drugs and range from benign effects such as dysphoria to more serious ones such as gastrointestinal disturbances, inappetence and may lead to a prolonged hospital stay. The use of pain scoring can ensure that the patient is given analgesia when appropriate and if opioids alone are insufficient despite changes in dosing then an additional analgesic class is introduced. This ensures that the lowest effective doses are utilised and that unwanted effects are minimised. 

What pain assessment tools are available?

There are a number of pain assessment tools available of which the most commonly utilised are discussed in more detail. The Glasgow short form of the canine acute pain scale and the feline acute pain scale are now widely used for assessment of acute and surgical pain in the clinical setting. The Colorado State University feline acute pain scale and the UNESP-Botucatu multidimensional composite pain scale for the assessment of postoperative pain in cats are also used in the clinical setting and have both advantages and disadvantages over the Glasgow tool. The rabbit grimace scale was designed for use in laboratory rabbits and has some limitations when assessing the animal directly due to changes in rabbit behaviour when faced with a potential predator species. 

The most important aspects of a pain assessment tool to consider are;
• They are a validated system, allowing reassessment
• They are easy to complete and assign a score to
• They are quick to complete in the clinical setting

An overview of the Glasgow short form of the canine composite pain scale, Glasgow feline composite pain scale and rabbit grimace scale are discussed further;

Pain assessment in dogs
The short form Glasgow composite measure pain scale (CMPS-SF) for dogs has been in use for around 10 years and was developed as a clinical tool from the full pain scale. It involves the completion and scoring of six descriptive categories and assignment of a final score out of 24, or out of 20 if the patient is non-ambulatory. The intervention score is set at 5/20 and 6/24 and is the level at which additional analgesia or a change in analgesic protocol is required. Following administration of additional analgesia, the patient should be reassessed following an appropriate time period to ensure the desired effect.

Pain assessment in cats
The Glasgow feline composite measure pain scale (CMPS-Feline) is a more recent development in the management of feline acute pain and utilises both scoring of six descriptive categories as well as assessment of facial geometry. The pain score is the sum of each of these seven categories and the maximum score is 20. The intervention level is set at 5/20, and as for the canine version this is score at which additional analgesia should be administered. Reassessment following an appropriate time period should be used to ensure any additional analgesia or change in protocol has a positive effect.

Pain assessment in rabbits?
The rabbit grimace scale was developed for use in the experimental laboratory setting and involves the assessment of five categories of facial expression, which comprise; orbital tightening, cheek flattening, nostril shape, whisker change and position and ear shape and position. Each of the categories or units is assigned a score from zero to two and a final score calculated. No intervention level is currently set, and therefore repeated scoring at regular intervals should be used to allow an assessment to be made. It is important to try to assess the rabbit from a distance to reduce any risk of behavioural changes due to human interaction. 

Summary

Pain assessment is a natural progression in the clinical environment to ensure the provision of good analgesia, minimise unwanted effects and deliver a positive hospital stay for our patients. The introduction of pain assessment requires a holistic approach by the entire veterinary team to ensure its success.

Article by
Carl Bradbrook
BVSc CertVA DipECVAA MRCVS

Originally published: Wednesday, 9th January 2019

References

Becker WM, Mama KR, Rao S, Palmer RH, & Egger EL. (2013) Prevalence of Dysphoria after Fentanyl in Dogs Undergoing Stifle Surgery. Vet Surg, 42 (3) pp 302-307.

Holton L, Pawson P, Nolan A, Reid, J, & Scott E. (2001) Development of a behaviour-based scale to measure acute pain in dogs. Veterinary Record, 148 (17) pp 525–531.

Keating SCJ, Thomas AA, Flecknell PA, & Leach MC. (2012). Evaluation of EMLA Cream for Preventing Pain during Tattooing of Rabbits: Changes in Physiological, Behavioural and Facial Expression Responses. PLoS ONE, 7 (9) e44437–11.

Lucas AN, Firth AM, Anderson GA, et al. (2001) Comparisonof the effects of morphine administered by constant-rate intravenous infusion or intermittent intramuscular injection in dogs. J Am Vet Med Assoc, 218 pp 884–891.

Reid J, Scott EM, Calvo G, & Nolan, A. M. (2017) Definitive Glasgow acute pain scale for cats: validation and intervention level. The Veterinary Record, 180(18) 449–449. 

Wolfe TM, Bateman SW, Cole LK, et al. (2006) Lidocaine infusion for postoperative analgesia. Vet Analg Anesth, 33 pp 328– 339.

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