ABSTRACT: Preventing pain has become an important goal for the veterinary team, despite the difficulties involved in pain recognition. A multi-dimensional approach to pain assessment, along with the use of a structured method of assessment is considered to be best practice.1 The implementation of a structured system for pain assessment within the veterinary practice will improve pain recognition and treatment, as the physical act of performing the assessment means that the individual's level of pain is considered. Veterinary nurses |VNs| can be involved in the assessment process and often have the most contact with in-patients and clients, so are ideally placed to recognise signs of pain and encourage treatment.
Preventing and managing pain has become an important goal for the veterinary team, despite the difficulties of pain recognition in a number of species. Hellyer et al. (2007) recommended that pain should be considered as the fourth vital sign and be incorporated into every patient assessment.2
VNs need to act as advocates for the animals in their care, and the inability of patients to communicate with veterinary staff increases this duty of care.3 An improved understanding of how pain occurs and an increased range of analgesic drugs has enabled clinical staff in veterinary practice to provide adequate multi-modal analgesia to every patient.
Despite these advances, management of pain can still be sub-optimal owing to inadequate recognition of the behavioural signs of pain and incorrect patient assessment. Often VNs are the main carers for in-patients and are a point of contact for owners, so they are ideally placed to assist owners and colleagues to identify pain.
Physiology of pain
Understanding how the body responds to – and deals with – pain is vital to its successful prevention and management. Following injury or noxious insult, inflammatory mediators are released at the site of tissue damage; these create a nociceptive response. Free nerve endings, called nociceptors, detect noxious stimulation and transmit the message via the spinal cord to the brain (Flaherty, 2009).4
The pathway between the site of injury and the brain is known as the pain pathway and it is a significant element in the body’s normal response to a painful stimulus.
Where there is ongoing or severe damage, a heightened response by the nociceptive receptors at the site of injury is seen. The reactive nociceptors also excite nearby dormant nociceptors to respond to the same stimulus, thereby causing an increase in the number of nociceptors at the site of injury. This is known as peripheral sensitisation.
A heightened response can also occur further along the pain pathway, in the spinal cord; this is known as central sensitisation.
Peripheral and central sensitisation can lead to ‘misinterpretation’ of noxious information travelling along the pain pathway to the brain. A result of this sensitisation can be a permanent state of pain or increased sensitivity, even when the initial injury has completely healed.4
This demonstrates the need for prevention of pain, rather than cure. Early administration of analgesia will slow or reduce the amount of nociceptive stimulation, leading to a decrease in pain felt by the patient and prevention of peripheral and central sensitisation.
Pain recognition
This is a crucial area, as recognition of pain must occur before treatment can begin. During nurse clinics, VNs can assist owners in recognising that their pet is experiencing a degree of pain, helping them to recognise the need for treatment.
‘Quality of life’ questionnaires can be a useful tool to help owners understand that their pet may not be coping as well with daily activities; they can also allow the veterinary team to implement interventions that target the areas in which the patient is struggling. For example, a patient with arthritis would potentially require a weight-loss programme and hydrotherapy alongside medical treatment.
Wiseman-Orr et aI. (2004) discussed the examination of 13 behavioural domains for assessment of dogs with chronic pain (Table 1). Each domain can be discussed with owners to highlight the need for treatment.
In most cases, the VN is the main carer of patients hospitalised at the practice and is ideally placed to identify signs of discomfort. Questionnaires – completed by owners on admission to the practice – containing information, such as usual toileting, eating, sleeping patterns and demeanour can assist in identifying behaviours that may indicate pain or are out of character for the individual.
VNs should actively look for signs of discomfort (Figures 1 & 2). The best way to achieve this is to adopt a standardised approach to the assessment of pain.
Figure 1: Cat showing hunched position following ovariohysterectomy
Figure 2: Dog showing obvious lameness. This patient was guarding the injured leg and was very worried and vocal when handled
Assessment
Pain is not objectively quantifiable and is highly variable across individuals (Hansen, 2003).6 As a result, pain assessment remains subjective and influenced by personal bias.4 This highlights the importance of multi¬dimensional pain assessment that is considerate of the individual’s personal experience.
The multi-dimensional approach considers both behavioural and physiological responses to pain alongside the patient’s usual demeanour (Table 2).1
It is important to remember that, although physiological variables can be useful, they may also be influenced by other factors such as stress and disease and should not be relied upon solely for the assessment of pain.
It is well documented that behaviours thought to be associated with pain are variable and alter with species, breed, age and environmental factors.2
Understanding normal behaviour is essential to identifying pain, selecting appropriate nursing interventions and helping the veterinary surgeon (VS) to provide suitable analgesia.
Challenges to assessment include consideration of personal experiences and preconceived ideas of the intensity of pain caused by surgical procedures.6 It is common for routine procedures to be thought of as less painful than non¬routine procedures, although the surgical approach may be similar.7
Pain assessment scales
Price and Nolan (2007) highlighted the importance of recognising that certain disease processes or sedation would reduce the patients ability to display behavioural indicators of pain.1 Although no 'gold standard’ method of pain assessment exists, a validated pain-scoring system for acute pain in canine patients, known as the Glasgow Composite Measure Pain Scale (GCMPS), is available.8
Although it can only be used postoperatively for assessment of acute pain in canine patients, it can be used as a model on which to base the design of a practice- specific system. It is expected that other validated systems will become available; but until then adapting human pain- assessment models is common practice.
Human pain scales mostly rely on self¬reporting of pain. Our patients, however, cannot speak to us, so the application of these systems to animals relies on interpretation of behaviour by an observer.9 This allows for bias owing to ‘inter-observer’ variability, so the use of a validated veterinary-specific method is preferred.
The importance of a structured, multi¬dimensional approach that is adopted by the whole team is essential to reduce inter-observer variability and ensure accurate assessment. It is recommended that a pain scale is used as an adjunct to a good clinical examination by the VS and that pain assessment is carried out frequently – both before and after analgesia is administered – in order to assess the patient’s response.
Treatment
Pre-emptive analgesia
The provision of analgesia prior to noxious insult will reduce the amount of postoperative pain, as it will reduce the nociceptive response. This is known as pre-emptive analgesia.'1
Multi-modal analgesia
Another way to ensure good pain relief is to provide multi-modal analgesia. Multi-modal analgesia is the use of two or more analgesic drugs, from different pharmacological classes, at the same time. The benefit of this approach is that the drugs will act at different sites along the pain pathway, resulting in improved control of pain.4
There is also a synergistic effect, meaning that individual drugs doses can be reduced, thus decreasing the risk of side effects. The multi-modal approach can also be considered for patients with more chronic pain.
The VN can assist owners with weight- loss plans, hydrotherapy and other alternative interventions that complement medical treatment, under the guidance of the VS. Patients hospitalised with chronic conditions, such as arthritis, can have preventive treatments – physiotherapy, short walks, harnessing or sling support, raised food bowls and thick bedding – included in their care plans.
Routes of administration
The route of administration of analgesic drugs also needs to be considered as it is best to administer the medication in the least stressful, but most effective, way. For example, in the case of severe or persistent pain, the use of a continuous rate infusion would be preferable to repeating intramuscular injections every four hours. This would provide a constant therapeutic effect by avoiding peaks and troughs in the level of analgesia.4
Parenteral administration is advantageous, as the onset of action is likely to be quicker than oral medication; but it can be difficult in animals that are fractious – either by nature or because they are in pain – so in some cases oral administration may be less stressful to the patient and will ensure that some analgesia is provided.
Evaluation
Following the administration of analgesia, it is important to assess the response to treatment. Pain is a personal experience and can change in intensity at any point. An analgesic protocol must meet the needs of the patient. Therefore, if a limited or negative response to analgesia is seen, a different dose or combination may be required and should be implemented as soon as possible.
Conclusion
The implementation of a structured system for pain assessment, within the veterinary practice, will improve pain recognition and treatment, because individual variation during the assessment process is reduced and the physical act of performing the pain assessment means that the individual’s level of pain is considered.
VNs have an important role to play in this, as they can carry out these assessments as part of an holistic approach to patient care, thus ensuring that suitable planning and analgesia administration is undertaken for all patients that have a requirement for pain relief.
VNs can also educate owners, who often put symptoms associated with pain in their pets down to old age and do not seek treatment. The multi-dimensional approach to pain management is paramount to ensure that pain is adequately prevented or reduced as much as possible.
Author
Lindsay Clapham BSc(Hons) CVN DipAVN(Small Animal) RVN
Lindsay is currently head nurse in a general small animal practice. She has a keen interest in in¬patient care, emergency and critical care, and pain management.
To cite this article use either
DOI: 10.1111/J.2045-0648 2012.00245.x or Veterinary Nursing Journal Vol 27 pp 446-448
References
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• VOL 27 • December 2012 • Veterinary Nursing Journal