Pain
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Clinical Trial Controlled Clinical Trial
The effect of ketamine on phantom pain: a central neuropathic disorder maintained by peripheral input.
Hyperactivity of N-methyl D-aspartate (NMDA) receptors may be one of the factors in the maintenance of persistent stump and phantom limb pain. Ketamine (bolus at 0.1 mg/kg/5 min followed by an infusion of 7 micrograms/kg/min) was administered intravenously to 11 patients with established stump and phantom limb pain in a double-blind saline-controlled study. All 11 patients responded with a decrease in the rating of stump and phantom limb pain assessed by visual analogue scale (VAS) and McGill Pain Questionnaire (MPQ). ⋯ Side effects were observed in nine patients. The results support the notion that stump and phantom pain are generated by activity in afferent fibres activated by mechanical but not by thermal stimuli and that the NMDA receptor is involved in the maintenance of postamputation pain states. NMDA receptor antagonists may have a potential in the treatment of stump and phantom limb pain.
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Experimental pain can elevate vibrotactile threshold, a phenomenon attributed in the literature to the operation of a 'touch gate.' It is not known, however, whether clinical pain produces similar effects. To explore this possibility, we measured vibrotactile threshold in patients with temporomandibular disorders (TMD) whose pain had a prominent myalgic component. Two-interval forced-choice tracking was used to determine threshold for a 25-Hz vibratory stimulus presented on the cheek. ⋯ These findings are consistent with the idea of a touch gate, and suggest the usefulness of further research in this area with clinical pain populations. The effects of an adapting stimulus (25 Hz, 20 dB SL) were also studied, and found to produce parallel elevations in vibrotactile threshold in the TMD and pain-free groups. This result indicates that at least some adaptation occurs at a higher (subsequent) level of somatosensory information processing than does the touch gating implied by the unadapted thresholds.
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In the present study, Brandtstädter's (1992) distinction between assimilation and accommodation as two fundamental means of coping is applied to the field of chronic pain. Assimilative coping involves active attempts (e.g. instrumental activities, self-corrective actions, compensatory measures) to alter unsatisfactory life circumstances and situational constraints in accordance with personal preferences. Conversely, accommodative coping (e.g. downgrading of aspirations, positive reappraisal, self-enhancing comparisons) is directed towards a revision of self-evaluative and personal goal standards in accordance with perceived deficits and losses. ⋯ Most important, the ability to flexibly adjust personal goals attenuated the negative impact of the pain experience (pain intensity, pain-related disability) on psychological well-being (depression). Furthermore, pain-related coping strategies led to a reduction of disability only when accompanied by a high degree of flexible goal adjustment. The theoretical and clinical implications of these findings for coping research and the treatment of chronic pain patients are discussed.
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Clinical Trial Controlled Clinical Trial
Independent effects of ischaemia and noradrenaline on thermal hyperalgesia in capsaicin-treated skin.
Noradrenaline increases thermal hyperalgesia in skin previously sensitized by capsaicin. The aim of the present study was to determine whether a vasoconstrictor ischaemic effect of noradrenaline increases thermal hyperalgesia. Heat pain thresholds were measured in the capsaicin-treated and untreated skin on the forearms of 13 normal volunteers. ⋯ Thermal hyperalgesia subsided in control sites in the capsaicin-treated skin after cuff pressure was released, but persisted at sites of noradrenaline iontophoresis (in the capsaicin-treated skin, mean heat pain threshold during reactive hyperaemia 45.2 +/- 5.1 degrees C at the noradrenaline site compared with 49.3 +/- 6.0 degrees C at control sites, P < 0.01; in the untreated skin, mean heat pain threshold at the noradrenaline site 46.5 +/- 3.3 degrees C compared with 48.8 +/- 3.0 degrees C at control sites, P < 0.001). Arterial occlusion could increase thermal hyperalgesia in capsaicin-treated skin by preventing the dispersal of nociceptive substances peripherally or through central summation of nociceptive signals. The hyperalgesic effect of noradrenaline is greater than the hyperalgesic effect of ischaemia, suggesting that some mechanism in addition to vasoconstriction contributes to the nociceptive effect of noradrenaline.
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This study examined the relative predictive validities of several measures of pain intensity. Forty chronic pain patients completed 6-14 days worth of hourly pain ratings, which were averaged to obtain a measure of actual average pain intensity. These patients then made ratings, on 101-point numerical rating scales, of worst, least, and usual pain during the previous 2 wks, and of their current pain. ⋯ Of all possible composites of usual, least, worst, and current pain ratings, the arithmetic mean of least and usual pain had the strongest relationship to actual average pain. The inclusion of ratings of most pain or current pain in any composite score actually weakened the relationship between the composite score and actual average pain intensity. These results suggest that, when clinicians or researchers wish to assess average pain among chronic pain patients, but cannot obtain multiple measures of pain over time, the most valid measure would be the arithmetic mean of patient-recalled least and usual pain.