Pain
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The purpose of this review is to identify important issues and to review the data that underlie the controversial effectiveness of opioids in relieving neuropathic pain. This controversy seems related to the use of multiple definitions of neuropathic pain together with its distinct mechanisms in both experimental animal models and human neuropathic pain syndromes, methodological shortcomings in available randomized controlled clinical trials, different methods of pain assessment, the inappropriate use of terms like efficacy and responsiveness, differential responses in spontaneous versus evoked pains, interindividual differences to specific opioids and opioid doses, and duration of follow-up. ⋯ Active placebo's mimicking side-effects should be included in the double-blind design, and control of unmasking should be performed. Individual titration of the opioid dose and active management of side-effects in long-term follow-up studies need to measure both pain relief and quality of life.
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To clarify the relationships between physical, and psychosocial components of chronic pain, a path analytic model was tested conceptualizing self efficacy as a mediator of disability. In turn, disability was hypothesized to mediate depression. This model could help explain the circumstances under which disability develops and why so many chronic pain patients become depressed. ⋯ Therefore, the lack of belief in ones own ability to manage pain, cope and function despite persistent pain, is a significant predictor of the extent to which individuals with chronic pain become disabled and/or depressed. Nevertheless, these mediators did not eliminate the strong impact that high pain intensity has on disability and depression. Therefore, therapy should target multiple goals, including: pain reduction, functional improvement and the enhancement of self efficacy beliefs.
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We studied the associations between psychosocial variables and sick-leave among patients with musculoskeletal pain. Patients (n = 586) seeking care to relieve their pain at health care and physiotherapy centres, completed a questionnaire about such variables as clinical characteristics (e.g. pain intensity), psychological well-being (e.g. burnout, depression) and coping strategies. The results show that the patients who had been on sick-leave for >30 days (n = 217), were significantly more often divorced, immigrants, blue-collar workers and less educated than the rest of the sample. ⋯ After controlling for possible confounders, multivariate regression analyses showed that the strongest predictors of the disability index were symptoms of burnout and posttraumatic stress reactions. The results confirm that emotional distress, coping style and perceived disability are associated with sick-leave, after controlling for pain parameters and sociodemographic variables. The high levels of emotional distress and the poor coping capacity reported by the patients with a long history of absence due to illness suggest that cognitive behavioural interventions ought to be integrated in the treatment of musculoskeletal pain.
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We investigated behavioral symptoms of neuropathic pain, and associated changes in dorsal horn neurons, in a rat model involving loose ligation of lumbar dorsal roots. The L4-L6 dorsal roots were exposed unilaterally and loosely constricted central to the respective ganglia with one (1-ligation) or two (2-ligation) silk 7-O ligatures. In control groups the dorsal roots were exposed but not ligated (sham-operated), or sutures were placed lengthwise between the dorsal roots (suture control). ⋯ Enlarged cutaneous receptive fields of dorsal horn neurons may contribute to mechanical allodynia associated with dorsal root constriction. However, the slow (>5 week) development of receptive field enlargement does not match the rapid development of allodynia. The lack of effect of dorsal root constriction on thermal sensitivity of dorsal horn units ipsilaterally corresponds to the lack of marked thermal hyperalgesia observed behaviorally.
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Clinical Trial Controlled Clinical Trial
Topical EMLA pre-treatment fails to decrease the pain induced by 1% topical capsaicin.
Topical capsaicin has been reported to be beneficial for the treatment of neurogenic pain. However, due to the burning pain associated with topical capsaicin, many patients discontinue treatment before therapeutic benefits are obtained. This study assessed the efficacy of EMLA (eutectic mixture of 2.5% prilocaine and 2.5% lidocaine) to block pain induced by the topical application of 1% capsaicin. ⋯ The 6 h treatment with high dose topical capsaicin (1%) produced significant desensitization to heat stimuli that was not affected by EMLA treatment. EMLA fails to produce a long lasting attenuation of the pain induced by topical application of 1% capsaicin. These results argue against the use of EMLA to block pain to topical capsaicin during the treatment of neurogenic pain.