Pain
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Review Meta Analysis
Health care practitioners' attitudes and beliefs about low back pain: a systematic search and critical review of available measurement tools.
The attitudes and beliefs that health care practitioners (HCPs) hold about back pain have been shown to affect the advice they provide to patients seeking healthcare. In order to develop a questionnaire for a national survey of attitudes, beliefs and practice behaviour of HCPs about back pain, a systematic review of available measurement tools was undertaken. Measurement tools were identified from a systematic search of databases (Medline, Embase, CINAHL, Psychinfo, AMED and British Nursing Index) in the English language for papers published from January 1990 to October 2006. ⋯ PT have undergone the most thorough testing to date, but gaps in the properties of all the tools remain, particularly test-retest reliability and responsiveness. This review identified only five tools and demonstrated limited reporting of their validity and reliability. Further development and testing of existing tools should be a priority to ensure they are robust and valid measures of attitudes and beliefs of HCPs about back pain.
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Randomized Controlled Trial
The effects of the TRPV1 antagonist SB-705498 on TRPV1 receptor-mediated activity and inflammatory hyperalgesia in humans.
TRPV1 is a cation channel activated by a range of noxious stimuli and highly expressed in nociceptive fibres. TRPV1 receptors are involved in pain and sensitisation associated with tissue injury and inflammation; hence, TRPV1 antagonists are potentially useful for the treatment of such pain states. SB-705498 is a potent, selective and orally bioavailable TRPV1 antagonist with demonstrated efficacy in a number of preclinical pain models. ⋯ The magnitude of the pharmacodynamic effects of SB-705498 appeared to be related to plasma concentration. These results indicate that SB-705498, at a clinically safe and well-tolerated dose, has target-specific pharmacodynamic activity in humans. These data provide the first clinical evidence that a TRPV1 antagonist may alleviate pain and hyperalgesia associated with inflammation and tissue injury.
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To evaluate changes in pain threshold before, during and after labor in a prospective clinical trial. Forty pregnant women at term were included. Pain threshold in 18 specific pressure points was evaluated using a dolorimeter. ⋯ Pain intensity using the VRS score was higher during labor than before labor (4.8+/-2.7 and 2.4+/-2.6 p<0.001). We found a significant rise in pain threshold during labor in term pregnancies. This rise may have an intended protective effect during the intense labor pain experience.
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Sex differences in endogenous pain modulation were tested in healthy volunteers (32 men, 30 women). Painful contact heat stimuli were delivered to the right leg alone, and then in combination with various electrical conditioning stimuli delivered to the left forearm. Four conditioning protocols were applied to each subject in separate sessions: mild, non-painful (control); distracting; stressful-yet-non-painful; strongly painful. ⋯ Regression analysis revealed that the magnitude of pain-evoked hypoalgesia was predicted by the perceived distraction (p=0.003) and stress (p=0.04) produced by the painful conditioning stimulation, providing evidence that distraction and stress contribute to pain-evoked hypoalgesia. However, the contribution of stress to pain-evoked hypoalgesia differed by sex (p=0.02), with greater perceived stress associated with greater hypoalgesia in men and the opposite trend in women, suggesting sex differences in the mechanisms underlying pain-evoked hypoalgesia. This study provides indirect evidence that multiple neural mechanisms are involved in endogenous pain modulation and suggests that sex-specific aspects of these systems may contribute to greater pain sensitivity and higher prevalence of many chronic pain conditions among women.
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There is evidence that elevated tissue concentrations of glutamate may contribute to pain and sensitivity in certain musculoskeletal pain conditions. In the present study, the food additive monosodium glutamate (MSG) was injected intravenously into rats to determine whether it could significantly elevate interstitial concentrations of glutamate in the masseter muscle and whether MSG administration could excite and/or sensitize slowly conducting masseter afferent fibers through N-methyl-D-aspartate (NMDA) receptor activation. The interstitial concentration of glutamate after systemic injection of isotonic phosphate-buffered saline (control) or MSG (10 and 50mg/kg) was measured with a glutamate-selective biosensor. ⋯ Intravenous injection of ketamine (1mg/kg), 5 min prior to MSG, prevented the MSG-induced decreases in the mechanical threshold of masseter afferent fibers. The present results indicate that a 2- to 3-fold elevation in interstitial glutamate levels in the masseter muscle is sufficient to excite and induce afferent mechanical sensitization through NMDA receptor activation. These findings suggest that modest elevations of interstitial glutamate concentration could alter musculoskeletal pain sensitivity in humans.