Pain
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Patients with fibromyalgia syndrome (FMS) report chronic pain related to abnormal sensitivity of muscles that is reflected by so-called tender points (TP). TP represent areas of abnormal mechanical pain thresholds that have only shown a minor correlation with clinical pain of FMS patients and seem to be better suited for predicting distress. Pain-related negative affect (PRNA), abnormal temporal summation of second pain (termed wind-up or WU), and abnormal WU decay are frequently present in FMS patients. ⋯ Hierarchical regression analysis demonstrated that the combination of PRNA ratings, TP count, and WU decay ratings predicted 49.7% of the variance of clinical pain in FMS. This model demonstrates independent relationships of biological and psychological factors to clinical pain and underscores the important role of abnormal peripheral and central pain mechanisms for FMS. Therefore, the combination of PRNA, TP count, and WU decay may provide an excellent measure for future clinical studies of FMS patients.
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Comparative Study
Body motion during repetitive isodynamic lifting: a comparative study of normal subjects and low-back pain patients.
To quantify performance differences between patients with low-back pain (LBP) and a control group during their performance of a repetitive isodynamic lifting task. Case-control study was done. LBP patients were recruited and tested at an outpatient ambulatory chronic pain rehabilitation program before treatment was begun. ⋯ Patients and controls also differed significantly on dynamic measures, particularly lifting speed and hip and knee temporal midpoints. Major static and dynamic motion differences were found between LBP patients and controls as they performed repetitive lifting under a constant load. These findings indicate that body motion parameters, in addition to more common strength and endurance measures, are necessary to describe the impact of persistent LBP on a person's lifting abilities.
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Genetic polymorphisms result in absent enzyme activity of CYP2D6 (poor metabolizers, PM) in about 10% of the Caucasian population. This study investigates whether the PM genotype has an impact on the response to tramadol analgesia in postoperative patients. A prospective study design was used and 300 patients recovering from abdominal surgery were enrolled. ⋯ PM for CYP2D6 showed a lower response rate to postoperative tramadol analgesia than EM. Therefore, CYP2D6 genotype has an impact on analgesia with tramadol. Pharmacogenetics may explain some of the varying response to pain medication in postoperative patients.
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Cognitive-behavioural models of chronic pain contend that appraisals of harm affect the individual's response to pain. It has been suggested that fear of pain and/or anxiety sensitivity predispose individuals to chronicity. According to this view, pain is maintained through hypervigilance towards painful sensations and subsequent avoidance. ⋯ However, selective attention appears to depend upon the nature of pain stimuli. For those who are highly fearful of pain they may not only selectively attend to pain-related information but have difficulty disengaging from that stimuli. Theoretical and clinical implications of the data are discussed.
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Secondary mechanical hyperalgesia has been demonstrated in postoperative patients indicating that central sensitization occurs after surgery. However, the underlying mechanisms are unknown. Here, we studied the role of spinal N-methyl-D-aspartate and alpha-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid (AMPA)/kainate receptors for pain behaviors indicating secondary hyperalgesia caused by gastrocnemius incision in the rat. ⋯ These results indicate that spinal sensitization contributing to behaviors for secondary hyperalgesia after incision requires Ca(2+) permeable AMPA/kainate receptors. The data further demonstrate that behaviors for secondary mechanical hyperalgesia after incision can be inhibited without affecting behaviors for primary mechanical hyperalgesia and guarding. Mechanisms for central sensitization causing secondary hyperalgesia in postoperative patients may therefore be separated from spontaneous pain and hyperalgesia that arises adjacent to the area of the incision.