By Ana Carina Costa, PgCertAVN Anaesthesia and Analgesia, NCert(Anaesth), NCert(PhysioTech),

Anaesthesia and Pain Clinic RVN

[email protected]

Learning Objectives:

• Recognise the physiological effects of pain

• Identify pain behaviours and body postures

• Appraise different pain scoring scales available for dogs and cats

• Understand how pain scoring can improve pain management

• How to implement pain scoring in practice

Pain scoring scales have become popular in veterinary medicine in the last decade as a tool to assess pain however, in busy practices and hospitals, it can be a challenging routine to implement often leading to the administration of prescribed analgesia without prior assessment or to suboptimal pain relief. A 2007 study evaluating the attitude of veterinary nurses in the UK using pain scoring systems revealed that only 8.1% of the practices were using formal pain scoring scales, despite 80% of participants agreeing that the scales are a useful tool¹. Furthermore, 96.8% of participants recognised that their knowledge of pain assessment could be improved¹. In a more recent survey to veterinarians and technicians in the USA, 47.6% reported using pain scoring scales routinely, 16.3% sometimes, and 36.1% not². The last group cited lack of training and busy caseload as the main reasons for not using pain scoring scales².

In human medicine, self-reporting pain using unidimensional scales is considered the most reliable and accurate way to assess pain. However, this may not always be possible, such as in the case of neonates, critical patients, and those with dementia, therefore multidimensional pain scoring scales are available to help assessing pain³.

Pain is a personal experience, and its perception depends on the intensity of the noxious stimulus and how an individual processes pain. Reporting pain for someone else, a human or a non-human animal, is challenging and subjective. The multidimensional systems are based on the evaluation of physiological, behavioural, postural, and facial expressions changes, therefore are more objective reliable than unidimensional scales that only assess pain intensity. In veterinary medicine, some of multidimensional pain scoring scales also include guidelines to adjust analgesia ⁴ ׳⁵.

Pain

The International Association of the Study of Pain describes pain as “An unpleasant sensory and emotional experience associated with, or resembling that associated with, actual or potential tissue damage” ⁶ and, highlights that the inability to communicate does not invalidate that a human or non-human animal is experiencing pain, as verbal description of pain is only one of various ways to express it ⁶.

In human medicine, pain is associated with sleep disturbances and depression, affects social relationships, ability to work, and enjoyment of life ⁷, conditions that we can relate to our veterinary patients, therefore pain management is a crucial part of nursing care.

Three types of pain are described in the literature ⁶ ׳⁸:

• Nociceptive/inflammatory - when somatic or visceral tissues are affected. Normally has protective nature and it is reversible, however, if not treated can progress from acute to a chronic state.

• Neuropathic – due to a primary lesion or disease in the central or peripheral nervous system. It can be reversed but also can progress to chronic pain.

• Neuroplastic – pain sensation without evidence of lesion. It is related to neuroplastic changes in the central nervous system (CNS) affecting the pain processing system causing a dysfunctional perception of pain. It is a consequence of long-term pain.

Physiological effects of pain and behavioural changes

Adequate pain relief improves patient care and clinical outcomes, while preserving the animal’s welfare ⁵ ׳⁶. Poor pain management can result in prolonged hospitalisation, suboptimal analgesia, and consequent physiological and behavioural changes. The administration of analgesia when is not necessary can lead to heavy sedation and/or dysphoric behaviours.

Pain has physiological effects on the body such as tachycardia and hypertension due to catecholamines release, lethargy, inappetence, pupil dilation, hypersalivation, hyperglycaemia, leucocytosis, cytokine production, immune suppression, and respiratory impairment ⁴ ׳⁵, increasing the risk of further complications, particularly after a surgical procedure.

It is important to recognise that some abnormal behaviours and body postures can be reflective of pain however, those may vary between species, breeds, and individuals ⁴. Painful patients may show signs of aggression or fear, self-trauma, vocalisation, and reluctancy to move and to be touched. Hunched and prayer position are often seen when the patient is experiencing abdominal pain, while low head carriage is associated with neck pain ⁴. When in doubt whether the animal is in pain or not, a low analgesia testing dose should be given and the patient re assessed. As animals are not aware that pain is temporary, a painful episode can lead to a traumatic experience and poor management of severe pain can result in central sensitisation leading to long-term pain ⁶.

Pain Scoring Scales

Pain scoring must be part of the pain management plan as it helps to ⁴:

˃ Encourages frequent patient monitoring

˃ Standardises pain assessment in the practice

˃ Supports clinical judgment

˃ Records trends and information for other team members

˃ Helps to recognise signs pain and quantity pain

˃ Validates if the analgesic treatment is working

˃ Allows analgesia adjustments by the VN when the veterinarian is not available

Some of the challenges that we may find pain scoring a patient include ⁴:

˃ Time

˃ Patient’s mentation & vocalisation

˃ Systemic disease

˃ Stress, fear, anxiety

˃ “Emergence delirium”

˃ Discomfort (e.g., full bladder)

Animals submitted to painful procedures should be regularly evaluated for pain, according to the time of the last dose of analgesic received and its duration of action ⁴. Care must be taken to not leave the postoperative patient without analgesia until experiencing pain. In addition, based on pain scoring we might be able to decrease the dose of systemic opioids when adopting a multimodal analgesia approach.

In veterinary medicine, the following pain scoring scales are validated ⁴׳⁵׳⁹:

For dogs:

• Glasgow Composite Measure Pain Scale (GCMPS) - is validated to assess acute pain and is based on six categories of behavioural descriptions, including the patient’s response to gentle palpation of the painful area. It is an objective numerical scale, there is a short version available easy to use but can be affected by the patient’s temperament. The maximum score is 24, and the cut-off score to administer rescue analgesia is ≥ 6/24. Available at https://www.newmetrica.com/acute-pain-measurement

• Colorado State University Veterinary Medical Center Acute Pain Scale - evaluates physiological behaviours and has drawings that help to use the pain scale. It includes gentle palpation of the painful area and has instructions not to disturb the patient if they are asleep. The maximum score is 4 and the analgesic plan should be reassessed when ≥ 2/4. Although it is available for cats is still not validated for feline species. Available at https://vetmedbiosci.colostate.edu/vth/services/anesthesia/animal-pain-scales

For cats:

• Feline Grimace Scale – is based on changes in facial expressions and does not require close interaction with the patient. Assesses the ear position, orbital tightening, muzzle tension, whisker, and head position. This pain scoring scale is easy to use and requires pre- and post-analgesia assessment. The maximum score is 10 and rescued analgesia must be administered when ≥ 4/10 ¹⁰. Available at https://www.felinegrimacescale.com.

• UNESP Botucatu Multidimensional Composite Pain Scale – evaluates pain expressions, reaction to palpation of the painful area, and psychomotor changes such as patient's posture, comfort, attitude, activity, and physiological variables. Although it is a comprehensive pain scale, it has the advantage of being available in eight languages and has a short version available. The maximum score is 30 (12), rescued analgesia must be administered when ≥ 8/30 or (≥ 4/12). Available at http://www.animalpain.com.br/en-us/.

• Glasgow Composite Measure Pain Scale (GCMPS) - is validated to assess acute pain and is based on six categories of behavioural descriptions, including the patient’s response to gentle palpation of the painful area. It is an objective numerical scale, there is a short version available easy to use but can be affected by the patient’s temperament. The maximum score is 20 in cats, and the cut-off score to administer rescue analgesia is ≥ 5/20. For cats includes the evaluation of facial expressions. Available at https://www.newmetrica.com/acute-pain-measurement.

For chronic pain assessment, the following pain scoring systems are available ⁴׳⁵:

• Feline Musculoskeletal Pain Index

• Canine Brief Pain Inventory

• Liverpool osteoarthritis in Dogs

• Helsinki Chronic pain Index

Pain is an individual experience and as its treatment. It is important to recognise that inadequate treatment of acute pain can result in behaviour changes and the appearance of chronic pain. Although pain scoring can be perceived as an extra and time-consuming task, veterinary nurses and technicians recognise it to be a valuable tool to improve pain management. Regular training and consistent use of pain scoring enhances the ability to identify pain and contribute to a greater nursing care.

References

1. Coleman DL, Slingsby LS. Attitudes of veterinary nurses to the assessment of pain and the use of Pain Scales. Veterinary Record. 2007;160(16):541–4. doi:10.1136/vr.160.16.541

2. Costa RS, Hassur RL, Jones T, Stein A. The use of pain scales in small animal veterinary practices in the USA. Journal of Small Animal Practice. 2022;64(4):265–9. doi:10.1111/jsap.13581

3. Severgnini P, Pelosi P, Contino E, Serafinelli E, Novario R, Chiaranda M. Accuracy of critical care pain observation tool and behavioural pain scale to assess pain in critically ill conscious and unconscious patients: Prospective, observational study. Journal of Intensive Care. 2016;4(1). doi:10.1186/s40560-016-0192-x

4. Clancy N, Sneddon C, Clancy N. Pain. In: The Veterinary Nurse’s Practical Guide to Small Animal Anaesthesia. 1st ed. UK: Wiley Blackwell; 2023. p. 269–95.

5. Self I, Grubb T. Physiology of Pain. In: BSAVA Guide to Pain Management in Small Animal Prac-tice. 1st ed. Gloucester, England: BSAVA; 2019. p. 3–13.

6. Raja SN, Carr DB, Cohen M, Finnerup NB, Flor H, Gibson S, et al. The Revised International Association for the Study of Pain Definition of pain: Concepts, challenges, and compromises. Pain. 2020;161(9):1976–82. doi: 10.1097/j.pain.0000000000001939

7. Moore A, Derry S, Eccleston C, Kalso E. Expect analgesic failure; pursue analgesic success. BMJ. 2013;346(may03 1). doi:10.1136/bmj.f2690

8. Adrian D, Papich M, Baynes R, Murrell J, Lascelles BD. Chronic maladaptive pain in cats: A review of current and future drug treatment options. The Veterinary Journal. 2017; 230:52–61. doi: 10.1016/j.tvjl.2017.08.006

9. Gruen ME, Lascelles BD, Colleran E, Gottlieb A, Johnson J, Lotsikas P, et al. 2022 AAHA pain management guidelines for dogs and cats. Journal of the American Animal Hospital Associa-tion. 2022;58(2):55–76. doi:10.5326/jaaha-ms-7292

10. Evangelista MC, Watanabe R, Leung VS, Monteiro BP, O’Toole E, Pang DS, et al. Facial expres-sions of pain in cats: The development and validation of a feline grimace scale. Scientific Re-ports. 2019;9(1). doi:10.1038/s41598-019-55693-8