The journal of pain : official journal of the American Pain Society
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Randomized Controlled Trial
Validation of the Short-form McGill Pain Questionnaire-2 (SF-MPQ-2) in acute low back pain.
The Short-form McGill Pain Questionnaire (SF-MPQ-2) assesses the major symptoms of both neuropathic and nonneuropathic pain and can be used in studies of epidemiology, natural history, pathophysiologic mechanisms, and treatment response. Previous research has demonstrated its reliability, validity, and responsiveness in diverse samples of patients with chronic pain. However, the SF-MPQ-2 has not been evaluated for use in patients with acute pain. Data were examined from a double-blind, randomized clinical trial of immediate-release tapentadol versus immediate-release oxycodone in patients with acute low back and associated radicular leg pain (N = 666). Analyses of internal consistency, convergent validity, and confirmatory factor structure were conducted using baseline data, and analyses of responsiveness were conducted using baseline and endpoint data. The SF-MPQ-2 total score and its 4 subscale scores (continuous pain, intermittent pain, predominantly neuropathic pain, and affective descriptors) generally showed good psychometric properties and 1) were internally consistent, 2) displayed good convergent validity, 3) fit the a priori factor structure, and 4) were highly responsive to analgesic treatment. These data extend previous evidence of the reliability, validity, and responsiveness of the SF-MPQ-2 in patients with chronic pain to those with acute low back and associated radicular leg pain. ⋯ Considered together with the results of other recent studies, the data suggest that the SF-MPQ-2 can provide a valid, responsive, and efficient assessment of both neuropathic and nonneuropathic pain qualities for clinical trials and other clinical research examining patients with various acute and chronic pain conditions.
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Instruments to assess chronic pain acceptance have been developed and used. However, whether and to what extent the content of the items reflects acceptance remain uninvestigated. A content analysis of 13 instruments that aim to measure acceptance of chronic pain was performed. A coding scheme was used that consisted of 3 categories representing the key components of acceptance, that is, disengagement from pain control, pain willingness, and engagement in activities other than pain control. The coding scheme consisted of 5 additional categories in order to code items that do not represent acceptance, that is, controlling pain, pain costs, pain benefits, unclear, and no fit. Two coders rated to what extent the items of acceptance instruments belonged to one or more of these categories. Results indicated that acceptance categories were not equally represented in the acceptance instruments. Of note, some instruments had many items in the category controlling pain. Further analyses revealed that the meaning of acceptance differs among different instruments and among different versions of the same instrument. This study illustrates the importance of content validity when developing and evaluating self-report instruments. ⋯ This article investigated the content validity of questionnaires designed to measure acceptance in individuals with chronic pain. Knowledge about the content of the instruments will provide further insight into the features of acceptance and how to measure them.
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Clinical neck pain affects pain sensitivity and coordination of neck muscles, but the impact on the shoulder muscles is unclear. This study investigated the effect of experimental neck pain on the activity of the axioscapular muscles during arm movements and changes in pain sensitivity. Experimental neck pain was induced in 24 healthy volunteers by injecting hypertonic saline into the splenius capitis. Isotonic saline was injected as control. Before, during, and after injections, electromyography was recorded bilaterally from 8 muscles during standardized arm movements (140° scapular plane elevation), and the root mean square amplitude was extracted. Likewise, pressure pain thresholds were assessed bilaterally on 3 sites. The root mean square electromyography was decreased for the ipsilateral upper trapezius (P < .01) and increased for the ipsilateral middle deltoid (P < .03) during upward movements. The root mean square electromyography was reduced for the ipsilateral upper trapezius (P < .01) during downward movement, whereas an increase was recorded in the contralateral external oblique (P < .02). At the injection site, the pressure pain threshold increased during pain compared with the post condition (5 minutes after potential pain had subsided; P < .03). In this study, trunk and axioscapular muscle activities were reorganized in response to localized and referred pain evoked by hypertonic saline injection into an intrinsic neck muscle with no direct attachments to the trunk or shoulder girdle. ⋯ Reorganized activity of the axioscapular muscles has been shown previously in neck pain patients and is believed to happen during the transition from acute to chronic pain. The present study demonstrates for the first time that such reorganization may happen acutely, adding to our understanding of the effects of acute neck pain.
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Current research on the risk of opioid analgesics with drug overdose does not account for the total morphine equivalent dose (MED) of opioids filled by a patient. In this study, time from first opioid prescription until drug overdose was examined for 206,869 privately insured patients aged 18 to 64 with noncancer pain and ≥2 filled prescriptions for Schedule II or III opioids from January 2009 to July 2012. Opioid therapy was examined in 6-month intervals including 6 months before an overdose and categorized as mean daily MED (0, 1-19, 20-49, 50-99, ≥100 mg) and total MED divided at top quartile (0, 1-1,830, >1,830 mg). Survival analysis was used, adjusting for demographics, clinical conditions, and psychoactive drugs. Relative to no opioid therapy, persons at highest risk for overdose (adjusted hazard ratios of 2-3) received a daily MED of ≥100 mg regardless of total dose or a daily MED of 50 to 99 mg with a high total MED (>1,830 mg). The hazard ratio was significantly lower (1.43, 95% confidence interval = 1.15-1.79) for 50 to 99 mg daily MED with a lower total MED (≤1,830 mg), whereas hazard ratios for lower daily MEDs did not differ by total dose. This analysis suggests that clinicians should consider total MED to assess risk of overdose for persons prescribed 50 to 99 mg daily MED. ⋯ When addressing risks for drug overdose, this analysis supports the need for clinicians, administrators, and policy makers to monitor not only daily opioid dose but also total dose for patients receiving 50 to 99 mg daily MED.
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Anecdotally, orofacial pain patients sometimes report that the painful face area feels "swollen." Because there are no clinical signs of swelling, such illusions may represent perceptual distortions. In this study, we examine whether nociceptive stimulation can lead to perceptual distortion of the face in a way similar to that of local anesthesia. Sixteen healthy participants received injections of .4 mL hypertonic saline to induce short-term nociceptive stimulation, .4 mL mepivacaine (local anesthetic) to transiently block nerve transduction, and .4 mL isotonic saline as a control condition. Injections were administered in both the infraorbital and the mental nerve regions. Perceptual distortions were conceptualized as perceived changes in magnitude of the injected areas and the lips, and they were measured using 1) a verbal subjective rating scale and 2) a warping procedure. Prior to the study, participants filled in several psychological questionnaires. This study shows that both nociceptive stimulation (P < .05) and transient blocking of nerve transduction (P < .05) can lead to perceptual distortion of the face. A test-retest experiment including 9 new healthy subjects supported the results. Perceptual distortions were positively correlated with the psychological variable of dissociation in several conditions (P < .05). Perceptual distortions may therefore be influenced by somatosensory changes and psychological mechanisms. ⋯ Knowledge of the factors that influence the perception of the face is important to understand the possible implications of perceptual distortions in orofacial pain disorders (and possibly other chronic pain states). Such information may ultimately open up new avenues of treatment for persistent orofacial pain.