Annals of medicine
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The concept and value of 'multimodal' or 'balanced' analgesia in the treatment of postoperative pain is reviewed. Based upon the relatively few multimodal studies compared to unimodal studies, it is concluded that a combination of analgesics will improve pain relief including movement-associated pain. Since analgesic combination therapy is rational, further studies are needed to evaluate the optimal combination for each surgical procedure, as well as to assess the risk of side effects and need for surveillance in large-scale studies.
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Recent research has demonstrated the increasing importance of the spinal cord in processing and modulating nociceptive input. Different groups of drugs, each acting by a unique mechanism, have been shown to block nociceptive afferent transmission. None of the currently available spinally administered local anesthetics, opioids or non-opioids produce analgesia without side effects. ⋯ Preliminary results suggest that the neuropeptide octreotide has potent analgesic effects. 'Balanced spinal analgesia' using a combination of low doses of drugs, with separate but synergistic mechanisms of analgesia, may produce the best results. The optimal drug combinations and dosages remain to be determined. It is essential that animal neurotoxicity studies followed by controlled clinical trials are performed before widespread spinal administration of new drugs.
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Many studies in several species, including humans, have identified a subset of primary afferent nerve fibres that are activated by potential or actual tissue-damaging stimuli. Discharge patterns of these nociceptive afferents faithfully reproduce some aspects of the applied stimuli (e.g. shape of the stimulus-response function) but not others (e.g. time-course of a sustained stimulus). ⋯ Therefore, the painfulness of a stimulus cannot be deduced from nociceptor discharges alone; central processing needs to be taken into account, particularly central summation. In addition to the immediate responses of nociceptive afferents to external stimulation, acute pain mechanisms also comprise the short-term plasticity of the nociceptive system as a consequence of prolonged noxious stimulation.