The journal of pain : official journal of the American Pain Society
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Transcutaneous electrical nerve stimulation (TENS) is an electrophysical modality used for pain management. This study investigated the dose response of different TENS intensities on experimentally induced pressure pain. One hundred and thirty TENS naïve healthy individuals (18-64 years old; 65 males, 65 females) were randomly allocated to 5 groups (n = 26 per group): Strong Non Painful TENS; Sensory Threshold TENS; Below Sensory Threshold TENS; No Current Placebo TENS; and Transient Placebo TENS. Active TENS (80 Hz) was applied to the forearm for 30 minutes. Transient Placebo TENS was applied for 42 seconds after which the current amplitude automatically reset to 0 mA. Pressure pain thresholds (PPT) were recorded from 2 points on the hand and forearm before and after TENS to measure hypoalgesia. There were significant differences between groups at both the hand and forearm (ANOVA; P = .005 and .002). At 30 minutes, there was a significant hypoalgesic effect in the Strong Non Painful TENS group compared to: Below Sensory Threshold TENS, No Current Placebo TENS and Transient Placebo TENS groups (P < .0001) at the forearm; Transient Placebo TENS and No Current Placebo TENS groups at the hand (P = .001). There was no significant difference between Strong Non Painful TENS and Sensory Threshold TENS groups. The area under the curve for the changes in PPT significantly correlated with the current amplitude (r(2) = .33, P = .003). These data therefore show that there is a dose-response effect of TENS with the largest effect occurring with the highest current amplitudes. ⋯ This study shows a dose response for the intensity of TENS for pain relief with the strongest intensities showing the greatest effect; thus, we suggest that TENS intensity should be titrated to achieve the strongest possible intensity to achieve maximum pain relief.
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The objective of this project was to determine the relationship between cigarette smoking and the reporting of chronic pain syndromes among participants in the Kentucky Women's Health Registry. Data was analyzed on 6,092 women over 18 years of age who responded to survey questions on pain and smoking. The chronic pain syndromes included in the analysis were fibromyalgia, sciatica, chronic neck pain, chronic back pain, joint pain, chronic head pain, nerve problems, and pain all over the body. Analyses controlled for age, body mass index, and Appalachian versus non-Appalachian county of residence. Results showed that women who were daily smokers reported more chronic pain (defined as the presence of any reported chronic pain syndromes) than women who were never smokers (adjusted odds ratio [aOR] = 2.04 and 95% confidence interval [CI] 1.67, 2.49). An increased risk was also seen for "some-day" smokers (aOR 1.68, 95% CI 1.24, 2.27), and former smokers (aOR 1.20, 95% CI 1.06, 1.37), though with less of an association in the latter group. This study provides evidence of an association between chronic pain and cigarette smoking that is reduced in former smokers. ⋯ This paper presents the association between smoking and musculoskeletal pain syndromes among Kentucky women. This finding may provide additional opportunities for intervention in patients with chronic pain.
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Evidence suggests large diameter afferents, presumably in response to centrally mediated changes, augment the mechanical allodynia or hyperalgesia seen in delayed onset muscle soreness (DOMS) conditions. Healthy males aged 18 to 30 (n = 16) performed eccentric exercise eliciting DOMS in the tibialis anterior muscle of a randomly assigned exercised leg. The contralateral leg served as a control. Mechanosensitivity was assessed on the exercised and control legs prior to and 24 hours postexercise via pressure pain thresholds (PPTs). PPTs were assessed at the muscle site, and at a distant segmentally related site, either without vibration or with vibration concurrently applied to the distant muscle, segmentally related, or control extra-segmentally related site. Participants completed a 6-point Likert scale providing a subjective measure of DOMS 5 days postexercise. Baseline mechanosensitivity was not significantly different at any site between the exercised and control legs prior to the exercise. Soreness ratings were higher 24 to 48 hours postexercise (P < .05), and baseline PPTs at the exercised legs muscle site decreased postexercise (P < .001). On day 1 following exercise, segmentally related site PPTs reduced significantly when vibration was applied concurrently to the DOMS affected tibialis anterior muscle (P < .04) compared to baseline mechanosensitivity or extrasegmental control vibration. ⋯ Further evidence is presented by this article indicating that large diameter afferents, presumably via centrally mediated mechanisms, augment the mechanical hyperalgesia seen in DOMS conditions. Future research examining eccentric activity in individuals with likely centrally sensitized conditions may be warranted.
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Case Reports
The contribution of sympathetic mechanisms to postamputation phantom and residual limb pain: a pilot study.
Postamputation pain (PAP) affects over 60% of major limb amputees. One of the main challenges in treating PAP is the difficulty involved in identifying pain mechanism(s), which pertains to both residual limb pain (RLP) and phantom limb pain (PLP). In this study, sympathetic blocks were performed on 17 major limb amputees refractory to treatment, including 2 placebo-controlled blocks done for bilateral amputations. One hour postinjection, mean RLP scores at rest declined from 5.2 (SD 2.8) to 2.8 (SD 2.6) (P = .0002), and PLP decreased from 5.3 (SD 3.1) to 2.3 (SD 2.1) (P = .0009). By 1 week, mean pain scores for RLP and PLP were 4.3 (SD 2.9) and 4.2 (SD 3.0), respectively. Overall, 8 of 16 (50%) patients experienced ≥50% reduction in RLP 1-hour postinjection, with the beneficial effects being maintained at 1 and 8 weeks in 4 and 1 patient(s), respectively. For PLP, 8 of 15 (53%) patients obtained ≥50% decrease in pain 1-hour postblock, with these numbers decreasing to 2 patients at both 1 and 8 weeks. In the 2 bilateral amputees who received controlled injections, mean PLP and RLP at rest scores went from 4.0 and 3.3 to 4.0 and 2.5 1-hour postblock, respectively, on the placebo side. On the treatment side, mean PLP and RLP scores decreased from 7.5 and 6.5, respectively, to 0. ⋯ The results of this study suggest that sympathetic mechanisms play a role in PLP and to a lesser extent, RLP, but that blocks confer long-term benefits in only a small percentage of patients.
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A burgeoning body of evidence supports the efficacy and elucidates the mechanisms of placebo analgesia. Debate persists, however, concerning their ethical use, with many of the present arguments being philosophically based. The present web-based study empirically investigated the acceptability of an analgesic placebo treatment. Participants (103) responded to vignettes depicting patients receiving a placebo analgesic. We experimentally manipulated: 1) placebo treatment instructions (level of deception); 2) treatment outcome; and 3) patients' pain severity. Participants rated vignettes on outcome measures of deception, physician-patient relationship, and patient mood. Participants then characterized a range of placebo acceptability through ratings of deceptiveness, effectiveness, and negative consequences. Results showed that placebos described as "medication shown to be a powerful analgesic in some people" were equally deceptive as those described as "standard drug treatment." Ratings of patient mood and physician approval were determined as much by treatment instruction as by treatment outcome and an analgesic response mitigated the negative consequences of deceptive administration. Participants tolerated moderate effectiveness and considerable negative consequences in an acceptable placebo, although results suggest lay individuals may not have a sophisticated conceptualization of placebo effectiveness. Studies altering individuals' understanding of placebo effectiveness and mechanisms are needed to identify additional factors determining placebo acceptability. ⋯ This study represents an empirical examination of analgesic placebo acceptability among lay individuals. This article is the first to systematically manipulate deception, treatment outcome, and disease severity to determine how these factors interact to differentially determine placebo acceptability-a highly relevant finding that informs the clinical use of placebo.