Pain
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Randomized Controlled Trial Clinical Trial
Effect of pre- or post-traumatically applied i.v. lidocaine on primary and secondary hyperalgesia after experimental heat trauma in humans.
Hyperalgesia on intradermal capsaicin application can be attenuated by systemic application of local anesthetics. We tested whether low doses of local anesthetics applied pre- or post-traumatically can reduce heat trauma-induced primary and secondary hyperalgesia in humans. Six healthy volunteers consented to the randomized, double-blind, and cross-over designed study. ⋯ Thus, local anesthetics at concentrations that do not block nerve conduction substantially affect ongoing central changes in pain processing that are induced by a real tissue trauma. A significant preemptive effect could not be demonstrated. The anti-hyperalgesic effect of lidocaine is likely based on action of central (spinal) sites, but peripheral sites may also be addressed.
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Our understanding of the natural history of chronic pain in the community is limited. This is partly due to the lack of a validated measure of chronic pain severity known to be responsive to change over time. The Chronic Pain Grade questionnaire has been shown to be valid and reliable for use in a general population as a self-completion questionnaire. ⋯ The majority of SF-36 scores changed in the hypothesized directions. Changes in CPG scores were significantly correlated with changes in most of the SF-36 domains. We concluded that the CPG is a useful and valid objective instrument for measuring change in severity of chronic pain over time and could be used in longitudinal studies of chronic pain severity.
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Possible role of inflammatory mediators in tactile hypersensitivity in rat models of mononeuropathy.
Peripheral hypersensitivity (hyperalgesia and allodynia) are common phenomena both in inflammatory and in neuropathic pain conditions. Several rat models of mononeuropathy (Bennett, Seltzer and Gazelius models) display such symptoms following partial injury to the sciatic nerve. Using immunohistochemistry and behavioral tests, we investigated inflammatory cell and cytokine responses in the sciatic nerve 14 days after injury created in these different models as well as after axotomy. ⋯ Our findings indicate that the considerable increase in monocytes/macrophages induced by a nerve injury results in a very high release of IL-6 and TNF-alpha. This may relate to the generation of tactile allodynia/hyperalgesia, since there was a clear correlation between the number of ED-1 and IL-6-positive cells and the degree of allodynia. It is possible that measures to reduce monocyte/macrophage recruitment and the release of pro-inflammatory interleukins after nerve damage could influence the development of neuropathic pain.