British medical bulletin
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Pain can either be 'nociceptor-mediated', produced as a consequence of the activation of high threshold nociceptors, or 'A-fibre mediated', resulting from the activation of low threshold A beta afferent fibres. Under normal circumstances nociceptor mediated pain only occurs in response to high intensity noxious stimuli. Following peripheral tissue injury the inflammatory reaction generates a complex set of chemical signals that alter the transduction properties of nociceptors such that they can be activated by low intensity stimuli, the phenomenon of peripheral sensitization. ⋯ This is the phenomenon of central sensitization. Because afferent inputs can provoke prolonged alterations within the central nervous system, optimal treatment of acute pain states should be directed both at abolishing peripheral sensitization and to preventing the establishment of central sensitization. The latter involves the strategy of pre-emptive analgesia.
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Psychological factors are contributory to the genesis and maintenance of many chronic pain syndromes. Treatment can be delivered either as one component of multimodal therapy or as the sole approach in a pain management programme. ⋯ Relaxation training is also of benefit. The documented success of these techniques in various settings suggests that psychological treatment should be considered a necessary component of any multidisciplinary clinic offering therapies to chronic pain sufferers.
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The clinical management of acute pain has been impeded by traditions and misconceptions which have resulted in suboptimal application to the patient of the currently available methods of pain control. The search for new drugs and exotic ways to deliver them has further obscured many of the basic principles which should guide management. Standard regimens fail because of the wide, unpredictable variability in pain intensity, patient characteristics, and pharmacological responses. ⋯ The delivery of opioid analgesics can be improved using patient controlled analgesia or spinal administration in some cases. Regional analgesia, often using simple techniques, can produce excellent pain relief. Overall management and staff education should be delegated to an acute pain service.
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Acute visceral pain is dull, aching, ill-defined, badly localized and often referred to remote areas of the body. These properties indicate that the representation of internal organs within the CNS is very imprecise. ⋯ The number of nociceptive afferent fibres in viscera is very small but these few nociceptive afferents can excite many second order neurones in the spinal cord which in turn generate extensive divergence within the CNS, sometimes involving supraspinal loops. Such a divergent input activates several systems--sensory, motor and autonomic--and thus triggers the general reactions that are characteristic of visceral nociception: a diffuse and referred pain, and prolonged autonomic and motor activity.
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Interest in the management and study of pain in children has increased in recent years. A range of techniques appropriate to children with different developmental levels is now available for the assessment of various aspects of childhood pain. A management plan can be developed depending on the cause of pain and choosing from a range of therapeutic techniques. ⋯ Suitable drugs are now available but inexperience and myths may still result in reluctance to use appropriate strong analgesics in children. Postoperative pain control and the analgesic needs of neonates have been particularly neglected areas. Management can be dramatically improved by increasing staff sensitivity and the use of an integrated programme of drugs, physical techniques and psychological approaches.