Pain
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Pain evaluation typically relies upon the use of self-report instruments. The validity of these tools is questionable in many older adults, however, particularly those with cognitive impairment. Rating of pain behavior (e.g. grimacing, sighing) by an objective observer represents an alternative pain assessment strategy which has been validated in subjects of heterogeneous ages. ⋯ The association between pain and disability was modestly strong with both self-report instruments and pain behavior observation when the ADL protocol was used, but not when the traditional protocol was used. Our findings suggest that pain behavior observation is a valid assessment tool in the elderly. In addition, it seems that observation of elders during performance of activities of daily living may be a more sensitive and valid way of assessing pain behavior than observing pain behavior during sitting, walking, standing, or reclining.
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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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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.
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Withdrawal responses to heat and mechanical stimuli applied to the plantar surface of the rat hindpaw were measured before and after an intraplantar injection of capsaicin. In separate groups of rats, capsaicin doses of 1, 10 and 30 micrograms, and the vehicle were given into the center of the plantar surface in a volume of 10 microliters. Withdrawal latency evoked by radiant heat and the frequency of withdrawal evoked by mechanical stimuli (von Frey monofilaments) were obtained from both hindpaws before and after injection. ⋯ Injection of the vehicle did not significantly alter withdrawal responses to heat or mechanical stimuli. These studies demonstrate that intraplantar injection of capsaicin in rats produces hyperalgesia to heat and mechanical stimuli. This model should be useful for correlative behavioral, physiological and pharmacological studies of underlying mechanisms of capsaicin-evoked hyperalgesia.
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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.