Chronic pain

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Introduction

In the Western World between about 1920 and 1980 the now universal use of strong opioids in terminal cancer patients with pain was strongly deprecated unless the patient was in the final days of life. This erroneous but well intentioned practice was based on the belief that "addiction" to strong opioids would in itself be harmful and that habituation to the analgesic effects of opioids would mean that when the symptoms were worst, in the final stages of the illness, they would be ineffective. This was manifestly unsatisfactory since about 70% of patients with widespread cancer suffer from significant pain. To meet this problem anaesthetists, mainly in the UK and North America, started clinics to offer peripheral and central nerve blocking procedures for cancer pain and modern pain clinics, mainly run by doctors whose background is anaesthesia, have evolved from this. Chronic pain services now have little to do with cancer pain as palliative care now manages these patients largely with systemic analgesics. Despite this anaesthetics is the parent speciality for chronic pain physicians and has provided an ever evolving literature for effective therapy in a challenging area of treatment[1], which has issues with complementary and alternative medicine that are not always effective[2].

Paradigms

Pain is a very common symptom. A wide variety of conditions present in pain clinics. Some will have already seen specialist physicians, others will be direct referrals from primary care. The origin of chronic pain medicine in terminal cancer tied the early pain clinics firmly to an anti-nociceptive paradigm. Cancer pain seems almost always to be driven by nociceptive input and many other painful conditions are basically nociceptive. It is however clear that many patients present with non-nociceptive pain. Many present with neuropathic pain for which the standard anti-nociceptive treatments or drugs are of limited value. Others seem to present with pain as an expression of suffering, fears or anxieties in their whole lives and prove refractory to most conventional medical interventions. Accurately knowing which of these mechanisms, which often co-exist, are present in any one patient is often difficult and often driven by the physician's personal ideas and elucidated by therapeutic failure.

References