Pain
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The aim of the study was to examine reproducibility of primary and secondary hyperalgesia in a psychophysical model of human inflammatory pain. Mild burns were produced on the crura of 12 volunteers with a 50 x 25 mm thermode (47 degrees C, 7 min). Assessments of (i) cold and warm detection thresholds, (ii) mechanical and heat pain thresholds, (iii) pain to heat (43 degrees C and 45 degrees C, 5 s), (iv) secondary hyperalgesia, and (v) skin erythema were made 1.75 and 0.5 h before, and 0, 1, 2, 4, and 6 h after a burn injury. ⋯ Habituation to the painful stimuli was demonstrated by significantly higher pain thresholds and lower pain responses on the second and third day of the study. The burn model is a sensitive psychophysical model of acute inflammatory pain, when cross-over designs and within-day comparisons are used, and the model is suitable for double-blind, placebo-controlled studies of analgesics. In similar models, we recommend that analgesic and placebo are evenly divided between right and left sides and study days.
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Wind-up and secondary hyperalgesia both are related to central sensitization, but whereas the former is explained by homosynaptic facilitation, the latter is due to heterosynaptic facilitation. To investigate possible interactions between both types of facilitation, we tested for alterations of perceptual wind-up in the secondary hyperalgesic skin zone adjacent to a capsaicin injection with light touch (by a cotton wisp) and punctate stimuli (calibrated von Frey hairs and pin pricks). Temporal summation of pain sensation (perceptual wind-up) was only observed with a clearly noxious stimulus (pin prick) presented at a repetition frequency of 0.6 s(-1), but not 0.2 s(-1). ⋯ Thus, the leftward shift of the stimulus response function fully accounts for all alterations of pain sensitivity to punctate stimuli in the zone of secondary hyperalgesia. We conclude that when the gain of spinal transmission was changed in secondary hyperalgesia, the gain of wind-up remained unchanged. These findings indicate that secondary hyperalgesia (heterotopic facilitation) and wind-up of pain sensation (homotopic facilitation) are independent phenomena.
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Gabapentin is an effective option for the treatment of neuropathic pain syndromes because of its efficacy and favorable side-effect profile. A case is presented of a 58 year old man who developed a painful polyneuropathy while being treated with gabapentin.
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Clinical Trial Controlled Clinical Trial
Learning to live with the pain: acceptance of pain predicts adjustment in persons with chronic pain.
When patients find their pain unacceptable they are likely to attempt to avoid it at all costs and seek readily available interventions to reduce or eliminate it. These efforts may not be in their best interest if the consequences include no reductions in pain and many missed opportunities for more satisfying and productive functioning. The purpose of this study was to examine acceptance of pain. ⋯ Regression analyses showed that acceptance of pain predicted better adjustment on all other measures of patient function, independent of perceived pain intensity. These results are preliminary. Further study will be needed to show for whom and under what circumstances, accepting some aspects of the pain experience may be beneficial.
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Myoclonus occasionally occurs in the perioperative setting and in patients on chronic opioid therapy. It appears to be dose-related in a unpredictable manner. Different mechanisms have been proposed to explain the occurrence of a series of neuromuscular disturbances probably sharing final common pathways. ⋯ Adjuvant drugs, such as benzodiazepines or dantrolene may avoid the reduction of the opioid dose while maintaining an acceptable analgesia. Current practice suggests a change in opioid when pain control is not obtained at opioid doses resulting in unacceptable adverse effects, including myoclonus and hyperalgesia. A change in the type of opioid may be useful in patients who develop severe central adverse effects, even if these patients appear to have normal renal function or hydration status.