Pain
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Comparative Study Controlled Clinical Trial
Effects of subcutaneous administration of glutamate on pain, sensitization and vasomotor responses in healthy men and women.
The present study aimed to investigate if (1) subcutaneous injection of glutamate induces pain, sensitization and vasomotor responses in humans and (2) if sex differences exist in these responses. Thirty healthy volunteers (men-15 and women-15) were included. Each subject received four subcutaneous injections (0.1ml; glutamate 100, 10, 1mM and isotonic saline 0.9%) into the forehead skin in two sessions separated by one week. ⋯ Concentration-dependent local vasomotor responses were found following the subcutaneous injection of glutamate but there was no sex difference in this effect. Glutamate 100mM significantly reduced the PPT values (P<0.001) without sex-related differences. The present study demonstrates for the first time that subcutaneous injection of glutamate evokes pain, vasomotor responses and pinprick hyperalgesia in human volunteers and that there are sex-related differences in some of these responses.
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Clinical Trial
The evaluation of acute pain in individuals with cognitive impairment: a differential effect of the level of impairment.
The present study investigated whether the level of cognitive impairment (CI) affects acute pain behavior and how it is manifested. Participants were 159 individuals (mean age 42+/-12), 121 with CI (divided into four groups according to the level of CI: mild, moderate, severe, profound) and 38 with normal cognition (controls). The behavior of the participants before and during acute pain (influenza vaccination) was coded by two raters with the Facial Action Coding System (FACS - scores facial reactions to pain) and the Non-Communicating Children's Pain Checklist (NCCPC-R - scores both facial and general body reactions). ⋯ In contrast, individuals with severe-profound CI exhibited high rates of "freezing reaction" (stillness) during vaccination, manifested mainly in the face and therefore resulting in elevation of only NCCPC-R scores but not of FACS's. The results suggest that the level of CI affects baseline as well as pain behavior and it is therefore necessary to choose an appropriate behavioral tool to measure pain in these individuals accordingly. For example, tools based on facial reactions alone might provide the false impression that individuals with severe-profound CI are insensitive to pain (due to freezing).
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Randomized Controlled Trial
Parental history of chronic pain may be associated with impairments in endogenous opioid analgesic systems.
A family history of chronic pain has previously been linked to increased incidence of spontaneous acute pain and risk for chronic pain. Mechanisms underlying these associations are unknown, although similar effects on both acute and chronic pain suggest that central endogenous analgesic system differences may be relevant. This study tested whether a positive parental chronic pain history (PH+) was associated with impaired endogenous opioid analgesic responses to acute pain. ⋯ A significant multivariate PHxSubject Type interaction (p<.05) indicated that opioid analgesic impairments were most prominent in PH+ LBP subjects. Similar analyses for finger pressure pain blockade effects were nonsignificant (p>.10). The possible heritability of endogenous opioid analgesic dysfunction observed in individuals with a positive parental chronic pain history remains to be investigated.
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The fear-avoidance beliefs of patients with subacute low back pain (LBP) considered at risk for chronic disabling LBP are not well known. The objectives of this cross-sectional descriptive survey, conducted in secondary care practice, were to assess fear-avoidance beliefs about back pain in patients with subacute LBP and to seek an association between physician or patient characteristics and level of fear-avoidance beliefs. A total of 286 rheumatologists completed a self-administered questionnaire assessing physicians' demographic, professional data, personal history of back pain, and back pain fear-avoidance beliefs (on the Fear-Avoidance Belief Questionnaire [FABQ]) and 443 patients with sLBP completed one on pain, perceived handicap and disability (Quebec Back Pain Disability Scale), anxiety and depression (Hospital Anxiety Depression questionnaire), and back pain beliefs (FABQ). ⋯ A total of 68% of patients and 10% of physicians had a high rating on the FABQ Phys (>14). Patients' fear-avoidance beliefs about physical activity were associated with low level of education (odds ratio [OR] 4.19; 95% confidence interval [CI] 1.83-9.57), patients' perceived disability (OR 1.05; CI 1.03-1.07), and physicians' high FABQ Phys score (OR 5.92; CI 1.31-26.32). Here we show that fear-avoidance beliefs about back pain were high in patients with subacute LBP and their rheumatologists.
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Suggestion for hypnotic analgesia aimed at a specific body area is termed "focused hypnotic analgesia". It is not clear, however, whether this analgesia is limited to a specific body location or spread all over the body. Focused hypnotic analgesia was studied, in response to ascending electrical stimuli, when analgesia and stimulation were applied to the same area (local), and when analgesia was applied to one location and stimulation was delivered to a different area (remote). ⋯ We conclude that in HH subjects focused hypnotic analgesia is mostly confined to the area aimed at, but some spread of analgesia to remote areas cannot be dismissed all together. Alternatively, this "spread" of analgesia could be due to a placebo effect in the remote area. Focused hypnotic analgesia requires increased attention to the body area aimed at, unlike analgesia achieved by distraction of attention.