The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
High levels of vicarious exposure bias pain judgments.
The present study evaluated the effects of exposure to facial expression of pain, on observers' perceptions of pain expression. Participants were undergraduates shown brief video clips of the facial expressions of shoulder-pain patients displaying no pain or moderate pain. Participants were randomly allocated to either a high preexposure condition in which each clip was preceded by 10 other clips showing strong pain or a no-exposure control. On each test trial, participants indicated whether they thought the person they saw was in pain or not. Data were analyzed using signal detection theory methods. High prior exposure to pain was unrelated to sensitivity to pain expression, but did significantly diminish the likelihood of judging the other to be in pain. Results are discussed in terms of their implications for pain judgments of health-care professionals, adaptation-level theory, and the psychophysical method of selective adaptation. ⋯ This paper provides an experimental demonstration that, when people have large amounts of exposure to others' expressions of pain, their estimation of others' pain is reduced. The findings offer 1 explanation for the widely observed underestimation bias in pain judgments and may suggest ways of changing it.
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This document reports the consensus of an interdisciplinary panel of research and clinical experts charged with reviewing the use of opioids for chronic noncancer pain (CNCP) and formulating guidelines for future research. Prescribing opioids for chronic noncancer pain has recently escalated in the United States. Contrasting with increasing opioid use are: 1) The lack of evidence supporting long-term effectiveness; 2) Escalating misuse of prescription opioids including abuse and diversion; and 3) Uncertainty about the incidence and clinical salience of multiple, poorly characterized adverse drug events (ADEs) including endocrine dysfunction, immunosuppression and infectious disease, opioid-induced hyperalgesia and xerostomia, overdose, falls and fractures, and psychosocial complications. Chief among the limitations of current evidence are: 1) Sparse evidence on long-term opioid effectiveness in chronic pain patients due to the short-term time frame of clinical trials; 2) Insufficiently comprehensive outcome assessment; and 3) Incomplete identification and quantification of ADEs. The panel called for a strategic interdisciplinary approach to the problem domain in which basic scientists and clinicians cooperate to resolve urgent issues and generate a comprehensive evidence base. It offered 4 recommendations in 3 areas: 1) A research strategy for studying the effectiveness of long-term opioid pharmacotherapy; 2) Improvements in evidence-generation methodology; and 3) Potential research topics for generating new evidence. ⋯ Prescribing opioids for CNCP has outpaced the growth of scientific evidence bearing on the benefits and harms of these interventions. The need for a strong evidence base is urgent. This guideline offers a strategic approach to creating a comprehensive evidence base to guide safe and effective management of CNCP.
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Randomized Controlled Trial
Ginger (Zingiber officinale) reduces muscle pain caused by eccentric exercise.
Ginger has been shown to exert anti-inflammatory effects in rodents, but its effect on human muscle pain is uncertain. Heat treatment of ginger has been suggested to enhance its hypoalgesic effects. The purpose of this study was to examine the effects of 11 days of raw (study 1) and heat-treated (study 2) ginger supplementation on muscle pain. Study 1 and 2 were identical double-blind, placebo controlled, randomized experiments with 34 and 40 volunteers, respectively. Participants consumed 2 grams of either raw (study 1) or heated (study 2) ginger or placebo for 11 consecutive days. Participants performed 18 eccentric actions of the elbow flexors to induce pain and inflammation. Pain intensity, perceived effort, plasma prostaglandin E(2), arm volume, range-of-motion and isometric strength were assessed prior to and for 3 days after exercise. Results Raw (25%, -.78 SD, P = .041) and heat-treated (23%, -.57 SD, P = .049) ginger resulted in similar pain reductions 24 hours after eccentric exercise compared to placebo. Smaller effects were noted between both types of ginger and placebo on other measures. Daily supplementation with ginger reduced muscle pain caused by eccentric exercise, and this effect was not enhanced by heat treating the ginger. ⋯ This study demonstrates that daily consumption of raw and heat-treated ginger resulted in moderate-to-large reductions in muscle pain following exercise-induced muscle injury. Our findings agree with those showing hypoalgesic effects of ginger in osteoarthritis patients and further demonstrate ginger's effectiveness as a pain reliever.
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Approximately 70% of male rats receiving severe T8 spinal contusions develop allodynia in T5-7 dermatomes (at-level) beginning 2 weeks after injury. In contrast, rats having either complete transections or dorsal hemisections do not develop allodynia at-level after chronic spinal cord injury (SCI). In the present study, incomplete laceration and contusion injuries were made to test for neuroanatomical correlates between areas of white matter damage/sparing at the lesion epicenter and the presence/absence of allodynia. After incomplete laceration lesions and 6 weeks of behavioral testing, histological reconstruction and analysis of the lesion epicenters revealed a significant difference (P < .001) in the amount of ventrolateral funiculus (VLF) asymmetry between rats showing pain-like responses evoked by touch (74.5% +/- 8.4% side-to-side difference in VLF damage) versus those not responding to touch (11.3% +/- 4.4% side-to-side difference in VLF damage). A 5-week mean allodynia score for each rat that incorporates a full range of forces that are all innocuous in intact controls revealed that the degree of hypersensitivity at level is related to the extent of VLF asymmetry after SCI. No other damaged spinal white matter or gray matter area was correlated with sensitivity to touch. Similar findings were obtained for rats receiving T8 contusions, a more clinically relevant injury. These data suggest that different extents of damage/sparing between the 2 sides of VLF probably are a requisite for the development of allodynia after SCI. ⋯ A side-to-side lesion asymmetry after chronic SCI in a rodent model was found to be highly correlated with the presence and degree of allodynia. Greater insight of key factors contributing to the development and maintenance of chronic neuropathic pain is important for improving quality of life.