European journal of pain : EJP
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Randomized Controlled Trial
Expectations modulate long-term heat pain habituation.
Habituation to pain was shown to be a complex mechanism involving the pain encoding regions and the antinociceptive system in the brain. Pain perception can be modulated by cognitive factors; however it is unclear whether cognitive factors also influence habituation to pain. We used an established experimental design with repetitive moderate painful heat stimulation over eight consecutive days. ⋯ However, it was abolished in the second (sensitize) and third (stable) group, but was very strongly demonstrated in the first (habituation) group. In this group, habituation tended to be increased as compared to the control group. In conclusion, our findings highlight the importance of context information in pain studies and contribute to our knowledge about pain processing and behaviour.
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Recently we demonstrated brush-evoked allodynia to be a partially graded phenomenon since increased brushing length and number of strokes significantly increased the brush-evoked pain intensity. In this study the influence of stroking velocity and brushing force on dynamic mechanical allodynia was examined in 16 patients with peripheral neuropathy. Brush-evoked allodynia was induced by lightly stroking 60mm of the skin twice with a 16 mm wide brush while varying stroking velocity (10, 20, 30 mm/s) and brushing force (10, 20, 40 g). ⋯ Higher maximum pain intensity was reported with higher brushing force. In conclusion, our findings demonstrated a significant relationship between the total brush-evoked pain intensity and stroking velocity as well as brushing force. Together with previously accumulated data these results substantiate the usefulness of this semi-quantitative assessment method in longitudinal studies on dynamic mechanical allodynia.
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Evaluating potentially analgesic effects of drugs and various treatments is critically dependent on valid animal models of pain. Since primary somatosensory (SI) cortex is likely to play an important role in processing sensory aspects of pain, we here assess whether monitoring SI cortex nociceptive C fibre evoked potentials can provide useful information about central changes related to hyperalgesia in rats. Recordings of tactile and CO(2)-laser C fibre evoked potentials (LCEPs) in forelimb and hind limb SI cortex were made 20-24h after UV-B irradiation of the heel at a dose that produced behavioural signs of hyperalgesia. ⋯ Tramadol, a centrally acting analgesic known to reduce hyperalgesia, induced changes that counteracted the changes produced by UV-B irradiation on transmission to SI cortex from the hind paw, but had no significant effect on time course of LCEPs from forelimb skin. Tactile evoked potentials were not affected by UV-B irradiation or tramadol. We conclude that altered sensory processing related to hyperalgesia is reflected in altered LCEPs in SI cortex.
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Randomized Controlled Trial Multicenter Study Comparative Study
A randomised controlled trial on the efficacy and side-effect profile (nausea/vomiting/sedation) of morphine-6-glucuronide versus morphine for post-operative pain relief after major abdominal surgery.
Morphine is the first choice of treatment of severe post-operative pain, despite the occurrence of often discomforting (post-operative nausea or vomiting (PONV)) and sometimes dangerous (sedation, respiratory depression) side effects. Literature data indicate that morphine's active metabolite, morphine-6-glucuronide (M6G), is a powerful analgesic with a possibly more favourable side-effect profile. In this multi-centre randomised controlled clinical trial patients undergoing major abdominal surgery were randomised to M6G or morphine treatment. ⋯ Sub-analysis showed a significant reduction in nausea levels in females on M6G (30% difference, P=0.034). In all patients, similar reductions of 30-35% were observed in anti-emetic use, vomiting, PONV (a combined measure of nausea and vomiting) in favour of M6G, persisting for the first 24h postoperatively. Reductions in sedation were observed in the first 4h post-operative period for M6G patients.
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Randomized Controlled Trial
Reference values of mechanical and thermal pain tests in a pain-free population.
Quantitative sensory tests are widely used in human research to evaluate the effect of analgesics and explore altered pain mechanisms, such as central sensitization. In order to apply these tests in clinical practice, knowledge of reference values is essential. The aim of this study was to determine the reference values of pain thresholds for mechanical and thermal stimuli, as well as withdrawal time for the cold pressor test in 300 pain-free subjects. ⋯ In conclusion, normative values of parameters related to pressure, heat and cold pain stimuli were determined. Reference values have to be stratified by body region, gender and age. The determination of these reference values will now allow the clinical application of the tests for detecting abnormal pain reactions in individual patients.