Pain
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Controlled Clinical Trial
A longitudinal study of the efficacy of a comprehensive pain rehabilitation program with opioid withdrawal: comparison of treatment outcomes based on opioid use status at admission.
Use of opioids for chronic non-cancer pain is controversial and the efficacy of comprehensive pain rehabilitation programs (CPRPs) that incorporate opioid withdrawal requires further investigation. We test the hypothesis that patients with chronic pain and longstanding opioid use who undergo opioid withdrawal in the course of rehabilitative treatment will experience significant and sustained improvement in pain and functioning similar to patients who were not taking opioids. A longitudinal design study compared 373 consecutive patients admitted to the Mayo Clinic Pain Rehabilitation Center at admission, discharge and six-month posttreatment by opioid status at admission. Measures of pain severity, depression, psychosocial functioning, health status, and pain catastrophizing were used to assess between- and within-group differences. Treatment involved a 3-week interdisciplinary pain rehabilitation program focused on functional restoration. Over one-half of patients (57.1%) were taking opioids daily at admission. The majority of patients (91%) completed rehabilitation and 70% of patients who completed the program returned questionnaires six months posttreatment. On admission, patients taking low- and high-dose opioids reported significantly greater pain severity (P=.001) and depression (P=.001) than the non-opioid group. Significant improvement was found on all outcome variables following treatment (P<.001) and six-month posttreatment (P<.001) regardless of opioid status at admission. There were no differences between the opioid and non-opioid groups upon discharge from the program or at six months following treatment. ⋯ Patients with longstanding CPRP on chronic opioid therapy, who choose to participate in interdisciplinary rehabilitation that incorporates opioid withdrawal, can experience significant and sustained improvement in pain severity and functioning.
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Local sensitization to noxious stimuli has been previously described in acute whiplash injury and has been suggested to be a risk factor for chronic sequelae following acute whiplash injury. In this study, we prospectively examined the development of tender points and mechano-sensitivity in 157 acute whiplash injured patients, who fulfilled criteria for WAD grade 2 (n=153) or grade 3 (n=4) seen about 5 days after injury (4.8+/-2.3) and who subsequently had or had not recovered 1 year after a cervical sprain. Tender point scores and stimulus-response function for mechanical pressure were determined in injured and non-injured body regions at specific time-points after injury. ⋯ Tenderness was found in the neck region and in remote areas in non-recovered patients. The stimulus-response curves for recovered and non-recovered patients were similar after 12 days and 107 days after the injury, but non-recovered patients had steeper stimulus-response curves for the masseter (p<0.02) and trapezius muscles (p<0.04) after 384 days. This study shows early mechano-sensitization after an acute whiplash injury and the development of further sensitization in patients with long-term disability.
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Despite the development of the IASP criteria, diagnosing complex regional pain syndrome (CRPS) remains a challenge because all symptoms vary interindividually, including the vascular abnormalities. Previous studies showed that skin temperature asymmetries between the affected and contralateral extremity around 2 degrees C are useful for diagnosing CRPS. However, they were either assessed only at one single point in time or during specific investigations including controlled thermoregulatory modulation of sympathetic activity which limits their practicability. ⋯ However, both patient groups differed significantly in parameters characterizing the skin temperature dynamics. A sum score (2 *Q Oscill +r2 id +DeltaT2) allowed diagnosing CRPS with a specificity of 67% vs. patients with other painful diseases and 79% vs. healthy controls (sensitivity: 73%, respectively, 94%) and reflected the severity of the dysfunction in CRPS better than the mean skin temperature side differences alone. The applied skin temperature analysis can be easily applied in the clinical settings and serves as a further facet in the difficult diagnosis of CRPS.
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Operant conditioning mechanisms have been demonstrated to be important in the development of chronic pain. Most experimental studies have investigated the operant modulation of verbal pain reports with extrinsic reinforcement, such as verbal reinforcement. Whether this reflects actual changes in the subjective experience of the nociceptive stimulus remained unclear. ⋯ Results demonstrated that sensitization to prolonged heat-pain stimulation was enhanced by operant learning within 1h. The extent of sensitization was directly dependent on the received magnitude of reinforcement. Thus, operant learning mechanisms based on intrinsic reinforcement may provide an explanation for the gradual development of sustained hypersensitivity during pain that is becoming chronic.
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P2X receptors on dorsal root ganglion (DRG) neurons have been strongly implicated in pathological nociception after peripheral nerve injuries or inflammation. However, nothing is known of a role for purinergic receptors in neuropathic pain produced by a chronic compression of DRG (CCD) - an injury that may accompany an intraforaminal stenosis, a laterally herniated disc or other disorders of the spine leading to radicular pain. In a rat model of DRG compression, hyperexcitable neurons retain functioning axonal connections with their peripheral targets. ⋯ These currents were accompanied by the generation of action potentials - but only in the CCD neurons. U0126, a specific inhibitor of the MEK1/2, greatly down-regulated the enhanced current. Taken together, these observations suggest that enhanced purinergic responses after CCD are mediated by P2X 3 receptors.