Palliative care: Managing chronic cancer pain
Patients, and even some health care professionals, believe that severe, uncontrollable pain is the inevitable consequence of a diagnosis of cancer. In reality, one-third of patients with cancer do not experience severe pain, and in those who do, the application of the basic principles of pain management set out in the World Health Organization (WHO) guidelines on cancer pain1 have been shown to relieve that pain in 88 per cent of cases.2 However, there is evidence of poor pain control in about one-third of patients in a general setting, compared with 5–10 per cent in specialist units.3,4 Most patients requiring palliative care are treated outside a specialist setting, such as in their own homes, in nursing homes or in acute hospitals. It is essential that all health care professionals have a good understanding of the basic principles of pain management, as this is applicable to patients in all care settings with various diseases.
Acute pain is short-lived and accompanied by adrenaline-mediated symptoms such as sweating, increased heart rate and respiration, and dilated pupils. The pain draws attention to an injury or illness. Most acute conditions heal and become pain-free within two to three weeks. In contrast, chronic pain is mostly continuous, and is generally accompanied by vegetative symptoms such as lethargy, anorexia, sleep disturbance and preoccupation with the pain. The physiological features characteristic of acute pain may be absent and the patient may not appear to be in pain.
Pain is subjective, and has been shown to be overestimated by relatives of the patient5 and underestimated by health care professionals.6 Wherever possible, the patient’s own description of the pain should be the basis of the overall assessment. Patients are often reluctant or reticent in describing their pain, out of the fear that new or increasing pain represents advancing disease or because they do not want to be a “bother”. A careful assessment of the patient is essential if good analgesia is to be achieved.7 A detailed history should be taken in order to determine the site(s), number, intensity, radiation timing and quality of pain. Any factors that aggravate or relieve the pain should be explored.8 A full analgesic drug history is also useful in determining a pain management plan. Pain in cancer patients can have a number of different causes as shown in Table 1, p216.
A number of validated pain assessment scales have been developed to enable the making of consistent, repeated assessments. Complex tools such as the McGill pain questionnaire9 are useful in research but are generally too time-consuming for daily use. Simpler scales such as visual analogues or numerical rating scales are more routinely used. It is rare for chronic pain to be simply a physical phenomenon: there are usually non-physical, as well as physical components. All pain assessment must include exploration of the social, psychological and spiritual components of the patient’s suffering. This can only be achieved if the patient is managed by a multidisciplinary team.
Physical pain can be broadly categorised into three groups:
- Somatic pain is associated with the activation of nociceptors in deep tissues such as bone. Pain is localised and constant and patients describe it as gnawing or aching
- Visceral pain results from activation of nociceptors in the visceral tissues of the thorax or abdomen. It is caused by infiltration, compression, distension or stretching of the viscera by tumour growth. Patients describe this pain as diffuse and constant
- Neuropathic pain occurs because of tumour infiltration into peripheral nerves or the central nervous system. There may be a background of burning or constricting sensations with paroxysmal or shooting pains
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Citation: Hospital Pharmacist URI: 10975249
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