Pain
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Abnormal return of cutaneous sensibility is common after burn injuries and many patients complain of painful and/or paresthetic sensations in their healed wounds. However, little is known about the exact nature and severity of these problems. The present study was designed to provide a quantitative evaluation of the cutaneous sensibility in burned patients. ⋯ When symptomatic and asymptomatic sites were compared, significant deficits were observed in the tactile modality (touch-pressure). Other significant predictors of chronic sensory problems were burn depth and patients' age. Pathophysiological mechanisms of diminished sensibility in burned and unburned skin as long as several years after the injury are discussed along with those implicated in pain and paresthesia problems reported by the patients.
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The mechanisms by which nerve growth factor (NGF) induces thermal hyperalgesia and neutrophil accumulation have been investigated in the rat. Thermal nociceptive thresholds in rat hind paw were measured as the time taken for paw withdrawal from a heat source and neutrophil accumulation was measured in hind paw and dorsal skin samples using a myeloperoxidase assay. NGF (23-80 pmol intraplantar (i.pl.) injection) induced a significant (P < 0.05, n = 6-16) thermal hyperalgesia at 5 h after injection and significant neutrophil accumulation (P < 0.05, n = 6) was observed with NGF (40 pmol). ⋯ The 5-lipoxygenase inhibitor ZM230487 (10 nmol co-injected with NGF) significantly attenuated neutrophil accumulation and hyperalgesia induced by NGF; unlike the histamine and 5-hydroxytryptamine antagonists (mepyramine and methysergide) which were without effect at the times measured. Furthermore, depletion of circulating neutrophils (using a rabbit anti-rat neutrophil antibody) abolished NGF induced hyperalgesia. These results indicate that neutrophils, which accumulate in response to a 5-lipoxygenase product, play a crucial role in NGF-induced hyperalgesia.
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Mexiletine is widely used for the treatment of neuropathic pain although its site(s) of action remain unclear. Here we have studied the effect of spinal administration of mexiletine (10-1000 microg) on the spontaneous and peripherally evoked responses of spinal neurones of nerve injured (selective ligation of spinal nerves L5-L6; SNL) rats. Sham controls for the surgical intervention were performed. ⋯ In addition, the mechanical punctate von Frey 9 and 50 g evoked neuronal responses of the SNL rats, but not sham operated rats, were significantly reduced by spinal mexiletine (F5,57 = 4.3, P < or = 0.002 and F5,52 = 6.1, P < or = 0.001). This pharmacological study suggests that following nerve injury there is a novel mexiletine sensitive spinal substrate which contributes to Adelta-fibre and C-fibre, but not Abeta-fibre, somatosensory transmission. This central action may underlie some of the clinical efficacy of mexiletine in the treatment of neuropathic pain states.
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Randomized Controlled Trial Clinical Trial
Sex differences in response to cutaneous anesthesia: a double blind randomized study.
The existing literature on experimentally induced pain indicates that there are sex differences, with females displaying greater sensitivity. In epidemiological studies, sex differences are also noted in the prevalence of a number of pain syndromes, with females reporting more severe pain, more frequent pain, and pain of longer duration. Complicating the interpretation of pain differences between men and women in clinical samples are reports of sex differences in response to pain-reducing medications. ⋯ This study did not show sex differences in the placebo condition. These results are particularly interesting in light of previous work that has shown similar pain stimuli (pressure pain) to be the stimulation most sensitive to sex differences. Results of this study suggest that the protocol employed (pressure pain stimulus with magnitude matching task) is sensitive to both anesthetic treatment and sex differences and represents an improvement in pain assessment methodology for use in experimental studies and in the clinic.
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The inability to predict outcome in patients with low back/neck pain leads to inappropriate or unnecessary treatment. The aims of the study were to identify prognostic factors for disability at 1-year follow-up in patients with back pain visiting primary care, and to compare the effect of these in two treatment strategies--chiropractic and physiotherapy. Data were taken from a randomised trial on patients with back/neck pain visiting the general practitioner, in which patients were allocated to chiropractic and physiotherapy as primary management. ⋯ Twelve per cent of the patients had poor prognostic factors (duration > or = 1 month, more than one localisation, low expectations of treatment and low well-being) at entry. These patients had a mean Oswestry score above 20% at 1-year follow-up. Clinical decision models for the management of patients with back pain visiting primary care that consider prognostic factors need to be implemented and prospectively evaluated.