The journal of pain : official journal of the American Pain Society
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The experience of pain is influenced by patients' personality, social and cultural background, and patient-doctor interaction. This study examines the role of self-reported pain, pain diagnosis, age, gender, depression, and the personality trait of self-criticism (defined as individuals' tendency to set unrealistically high self-standards and to adopt a punitive stance toward one's self), in determining physicians' view of expected prognosis in response to chronic pain management. Before the first visit to a tertiary chronic pain clinic, patients provided information regarding their perceived pain, depression, and self-criticism. Immediately subsequent to the visit, physicians' evaluated expected prognosis. Participating physicians were blinded to the patient's psychosocial variables collected. Sixty-four patients with chronic pain (34 women and 30 men) with various diagnoses were included. Patients' age, gender, pain diagnosis, self-reported pain, and depression did not significantly correlate with physician's estimation of expected prognosis. In contrast, patients' self-criticism emerged as an independent predictor of physicians' pessimism regarding outcome. Thus, in the chronic pain clinic setting, patients' personality, rather than self-reported pain experience, determines doctor's clinical judgment of expected prognosis. ⋯ Chronic pain is a multimodal negative experience that is determined by physiological, cognitive, personological, and interpersonal factors. In line with this observation, we found patients' personality, specifically, their self-criticism, determines physicians' clinical judgment of expected prognosis.
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Repeated daily application of transcutaneous electrical nerve stimulation (TENS) results in tolerance, at spinal opioid receptors, to the antihyperalgesia produced by TENS. Since N-methyl-D-aspartate (NMDA) receptor antagonists prevent analgesic tolerance to opioid agonists, we hypothesized that blockade of NMDA receptors will prevent tolerance to TENS. In rats with knee joint inflammation, TENS was applied for 20 minutes daily at high-frequency (100 Hz), low-frequency (4 Hz), or sham TENS. Rats were treated with the NMDA antagonist MK-801 (0.01 mg/kg to 0.1 mg/kg) or vehicle daily before TENS. Paw withdrawal thresholds were tested before and after inflammation and before and after TENS treatment for 4 days. On day 1, TENS reversed the decreased mechanical withdrawal threshold induced by joint inflammation. On day 4, TENS had no effect on the decreased withdrawal threshold in the group treated with vehicle, demonstrating development of tolerance. However, in the group treated with 0.1 mg/kg MK-801, TENS significantly reversed the mechanical withdrawal thresholds on day 4, demonstrating that tolerance did not develop. Vehicle-treated animals developed cross-tolerance at spinal opioid receptors. Treatment with MK-801 reversed this cross-tolerance at spinal opioid receptors. In summary, blockade of NMDA receptors prevents analgesic tolerance to daily TENS by preventing tolerance at spinal opioid receptors. ⋯ Observed tolerance to the clinical treatment of TENS could be prevented by administration of pharmaceutical agents with NMDA receptors activity such as ketamine or dextromethorphan.
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Visceral injury has been shown to alter somatic sensitivity, but little is known about the effect of somatic insult on the viscera. In the present study, we examined (1) the effect of colon inflammation on somatic sensitivity and (2) the affect of hind paw incision on colon sensitivity. After intracolonic administration of trinitrobenzene sulfonic acid (TNBS) or zymosan, visceromotor responses to colorectal distension were increased to post-treatment day 8. Mechanical withdrawal thresholds in the hind paw were decreased in TNBS- and in zymosan-treated rats until post-intracolonic treatment day 2. There was no change in hind paw heat withdrawal latency in either group. Plantar incision of the hind paw resulted in a decrease in both hind paw mechanical withdrawal threshold and heat withdrawal latency and significantly increased the visceromotor response to colorectal distension from postincision days 1 to 8. The colon hypersensitivity was of longer duration than hyperalgesia at the site of hind paw incision. These results support the hypothesis that somatic injury and visceral inflammation can alter central processing of visceral and somatic inputs, respectively. ⋯ Surgical procedures are common and typically associated with hyperalgesia at and around the site of incision. This report establishes in a model of postsurgical pain and hyperalgesia that a long-lasting visceral hypersensitivity may also accompany postsurgical hyperalgesia.
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Transcutaneous electric nerve stimulation (TENS) is a noninvasive treatment used in physiotherapy practice to promote analgesia in acute and chronic inflammatory conditions. The aim of the present study was to investigate the action mechanism of TENS at high (HF: 130 Hz) and low (LF: 10 Hz) frequencies in an inflammation model produced by the injection of carrageenan in rat paws (Cg; 250 microg). After carrageenan administration (0 time), either HF or LF TENS was applied to the inflamed paw of rats for 20 minutes, and hyperalgesia was assessed hourly using the modified Randall-Selitto method (1957). HF and LF TENS inhibited the carrageenan-induced hyperalgesia by 100%. Pretreatment of animals with intraplantar naltrexone (Nx; 50 microg) reversed the analgesic effect of the LF TENS but did not alter the effect of HF TENS. The application of HF and LF TENS to the contralateral paw reversed the hyperalgesia of the inflamed paw similar to that observed when TENS was applied to the inflamed paw. However, LF TENS presented a longer-lasting analgesic effect than HF TENS. Our data demonstrate that HF and LF TENS induced antihyperalgesia. We also report that the antihyperalgesia provoked by LF TENS is partially due to the local release of endogenous opioids. ⋯ This study offers important information about physiotherapy practices aimed at pain relieving. TENS is a noninvasive treatment that promotes analgesia in acute and chronic inflammatory conditions. Scientists, patients, and the general population may benefit from this knowledge.
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A randomized, double-blind, placebo-controlled trial was conducted to determine the benefit of nabilone in pain management and quality of life improvement in 40 patients with fibromyalgia. After a baseline assessment, subjects were titrated up on nabilone, from 0.5 mg PO at bedtime to 1 mg BID over 4 weeks or received a corresponding placebo. At the 2- and 4-week visits, the primary outcome measure, visual analog scale (VAS) for pain, and the secondary outcome measures, number of tender points, the average tender point pain threshold, and the Fibromyalgia Impact Questionnaire (FIQ), were evaluated. After a 4-week washout period, subjects returned for reassessment of the outcome measures. There were no significant differences in population demographics between groups at baseline. There were significant decreases in the VAS (-2.04, P < .02), FIQ (-12.07, P < .02), and anxiety (-1.67, P < .02) in the nabilone treated group at 4 weeks. There were no significant improvements in the placebo group. The treatment group experienced more side effects per person at 2 and 4 weeks (1.58, P < .02 and 1.54, P < .05), respectively. Nabilone appears to be a beneficial, well-tolerated treatment option for fibromyalgia patients, with significant benefits in pain relief and functional improvement. ⋯ To our knowledge, this is the first randomized, controlled trial to assess the benefit of nabilone, a synthetic cannabinoid, on pain reduction and quality of life improvement in patients with fibromyalgia. As nabilone improved symptoms and was well-tolerated, it may be a useful adjunct for pain management in fibromyalgia.