ABSTRACT: Advances in veterinary medicine mean that pets are living longer, with many diseases of old age, such as cancer, being managed long term. Management of pain in these patients is essential to maintain optimum quality of life. To achieve this, pain must be recognised and treated appropriately, through constant re-evaluation, tailoring analgesia to address patients' changing needs. As in many areas of cancer treatment, veterinary nurses have an essential role to play in comfort management.

This article* aims to overview the options available – from pharmacological strategies, to nursing care, both in the hospital environment and at home, in conjunction with owners.

One of the main goals of treatment in the majority of veterinary oncology is maintenance of optimum quality of life, as opposed to quantity, in cancer-bearing pets. Cancer can be a painful disease, and to provide acceptable quality of life, pain must be recognised and treated appropriately, through constant re¬evaluation, tailoring of analgesic protocols to address patients changing needs and being prepared to re-think/ change the plan whenever appropriate.

Sources of pain in cancer patients

Whilst there have been few clinical studies into cancer pain in animals, it must be assumed – based on clinical experience and information extrapolated from human medicine and knowledge of other chronic pain states, such as osteoarthritis – that veterinary cancer patients experience pain.

Whilst not all tumours are painful, and individual patients may react to/perceive pain differently, any tumour may cause pain. In general, it is thought that the initial and most common cause of pain is tumour invasion into body tissues – this may cause tissue-stretching, compression or ischaemia, resulting in visceral or neuropathic pain. Masses which are space-occupying, pressing on/trapping nerves or other structures, or those which have ruptured or ulcerated, are all sources of pain (Figure 1).

Figure 1: Tissue-stretching and compression in this tumour over the temporomandibular joint were extremely painful, and prohibiting normal movement and resulting in anorexia and dehydration

Diagnostic procedures may be mildly to severely painful, depending on their nature. So cancer-related pathologic fractures are a source of severe acute pain, as are therapeutic surgical procedures; and potentially, if complications occur, chemotherapy (extravasation, for instance) and radiotherapy (desquamation, for example) may cause pain, whilst chronic neuropathic pain may occur as a secondary consequence of nerve damage.

It should be remembered that many cancer patients are older and may suffer from pre-existing chronic pain -such as occurs in osteoarthritis – which should be treated concurrently.

Reasons to treat pain

Pain is the awareness of suffering, distress, an unpleasant physical or emotional experience associated with potential or actual tissue damage. It is sensed and transmitted by nociceptive free nerve endings, which are abundant in superficial and deep body tissues. Compassionate care requires that patients are kept as free as possible from the adverse effects associated with cancer and its treatment.

There are multiple deleterious sequelae associated with uncontrolled pain, which could negatively impact on oncology patients’ health state. These include anorexia (often in hypermetabolic patients); biological and psychological effects, which may result in a ‘stress response’ (release of cortisol and catecholamines, resulting in catabolism, adverse effects on cardiorespiratory function, as well as delayed healing); and/or behavioural changes such as depression, aggression, restlessness/ insomnia and self trauma. Alterations in nociception may also occur, resulting in hyperalgesia, allodynia, with or without ‘phantom’ pain, all of which are serious problems and may be difficult to treat.

Pain management strategies

Strategies for managing pain are based on the concept of interfering with nociception – the conscious perception of pain. Providing analgesia before painful stimuli initiate nociception is termed pre-emptive analgesia, and should be employed whenever possible in oncology patients. Untreated pain causes central-sensitisation (‘wind up’), which often occurs in ongoing chronic pain syndromes, such as cancer.

Many cancer patients undergo multiple procedures during the course of their therapy, anxiety and fear can become a significant part of the pain experience – use of sedation in combination with pre-emptive analgesic drugs, may relieve some of this stress.

For moderate to severe cancer pain, full agonist opioids are the drugs of choice. These should be titrated to patient needs, with careful monitoring for efficacy and/or unwanted side effects, such as dysphoria, sedation, respiratory depression, bradycardia and reduced gut motility. 

Regional nerve blocks may be incorporated into anaesthetic protocols for surgical oncology patients. Extradural blocks may be administered to provide analgesia for up to 24 hours; or analgesic catheters, placed at surgery, may be infused with local anaesthetic (Figure 2).

Figure 2: Extradural injection of bupivicaine and morphine in a feline patient about to undergo hind limb surgery

Painful surgeries require intraoperative analgesic supplementation – constant rate infusions (CRI) and nitrous oxide help control emergent pain, with CRIs continued postoperatively as required (Figure 3). Patients with mild to moderate postoperative pain may be managed with intermittent boluses, but it is imperative to anticipate the need for further analgesic before the effect of the previous dose has worn off, with regular patient assessment to avoid overdose.

Figure 3: Fentanyl, lidocaine and ketamme continuous rate infusion being delivered by syringe-driver to a patient recovering comfortably from a median strenotomy

For longer term pain management, the use of NSAIDs, often in combination with a partial or full opioid, is a good option. This targets multiple points along the pain pathways, allowing reduction of the doses of each drug and creating balanced analgesia. 

Some specific examples of pharmacological options are listed in Table 1.

Various doses and/or drugs may have to be tried to meet an individuals needs. However, if pain is sufficiently severe as to cause drugs doses to be repeatedly elevated, or pain is uncontrolled, quality of life and the ethics of pursuing treatment in terminally ill patients must be questioned.

Nursing man
agement

Nursing staff have an essential role to play in the pain management of oncology patients. In conjunction with drug therapy, patient comfort may be optimised by provision of excellent nursing – frequent monitoring, ensuring patient comfort, minimising stress and provision of appropriate nutrition, for example.

Simple things, such as regular interaction with the patient and quiet companionship; gentle grooming, massage and physiotherapy, and/or the application of heat packs, can have a real impact on their comfort (Figure 4). Judicious use of Elizabethan collars will prevent self trauma, which would exacerbate pain, and the importance of this should be impressed on owners to ensure compliance (Figure 5).

Figure 4: Good monitoring, regular interaction and quiet companionship can have a real impact on patient comfort

Figure 5: Appropriate application of Elizabethan collars will prevent self-trauma, which would otherwise exacerbate pain

In order to ensure effective analgesia, recognition and monitoring pain is paramount. Various pain scoring systems exist and can be employed to help maintain objectivity and continuity. Nursing staff should be aware of physical and behavioural signs which could be considered to be pain related. These may include vocalization, tachypnoea +/- tachycardia, pyrexia, inappetence, lameness/ loss of function, aggression/ resentment of handling/ unresponsiveness to handling, restlessness/ inability to settle/sitting hunched or in unnatural positions, altered facial expression. Any of these signs should be recorded and brought promptly to the attention of the veterinary surgeon. It should be remembered that some animals will not show obvious/classic’ signs of pain. If there is any doubt, analgesia should be provided.

Pain clinics may be established to regularly re-assess pain and quality of life in out-patients, check compliance, and discuss owner concerns. In general, owners of cancer-bearing pets are very committed and it is important that there is a close communication between them and the nursing team. The patient’s appetite, willingness to exercise/play, its interaction with family/other pets and general demeanour, as well as the owners perception of the pet’s pain/overall quality of life may be used to measure the success of treatment.

Conclusion

By understanding and recognising cancer pain, veterinary nurses can be proactive in identifying the level of analgesia required for individual patients, providing compassionate care and managing the long-term comfort of cancer patients and have a real impact on outcome. 

Author

Linda Roberts

Dip AVN (Medical) VTS (Oncotogy) RVN

Linda Roberts qualified as a VN in 2002 whilst in general practice.

She then worked at the RVC, London, before moving to the University of Edinburgh's Hospital for Small Animals in 2004. There she obtained the Diploma in Advanced Veterinary Nursing (Medical) in 2005, before taking up the position of oncology nurse with the Cancer Service in 2006.

In 2009, Linda became a veterinary technician specialist in oncology and a member of the Academy of Internal Medicine for Veterinary Technicians. She also has strong interests in analgesia, clinical nutrition, medical nursing and the maintenance of optimum quality of life in chronically ill patients.

To cite this article use either

DOI: 10.111l/j.2045-0648.2011.00047.x or Veterinary Nursing Journal Vol 26 pp 268-271

Further reading

GAYNOR. S. I2008I Control of Cancer Pain in Veterinary Patients Vet Clinics of North America 38: 1429-1448. Elsevier. USA LASCELLES. B. DUNCAN X. 120071 Supportive Care for the Cancer Patient Management of Chronic Cancer Pam Withrow & MacEwen's Small Animal Clinical Oncology 4th Edition Eds Withrow & Vail. Saunders Elsevier. USA LASCELLES. B DUNCAN X. 12003). Relief of Chrome Cancer Pain'. BSAVA Manual of Canine and Feline Oncology 2nd Edition. Eds Dobson & Lascelles BSAVA Gloucester BSAVA Manual of Small Animal Anaesthesia and Analgesia 119991. Eds Seymour & Gleed. BSAVA Gloucester.

Pam Management in Animals 12000], Eds Flecknell & Waterman-Pearson Saunders. London

 

 

Veterinary Nursing Journal • VOL 26 • August 2011 •