The journal of pain : official journal of the American Pain Society
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Intramuscular injection of hypertonic saline produces a dull ache that is felt in the muscle belly but also often refers into distal structures. We have previously observed in 2 subjects that the pattern of pain referral alters during painful stimuli separated by a week. In this investigation, we tested the hypothesis that the intensity and area of pain in the local and referred regions exhibits plasticity when an identical noxious stimulus is delivered to the same site over sequential trials. Bolus 1 mL intramuscular injections of 5% hypertonic saline were made into the same site of the tibialis anterior (TA) muscle on the same day each week for 4 consecutive weeks. Twenty-one subjects mapped the areas of local and referred pain and rated the intensities on a visual analog scale every 30 seconds until the cessation of pain. Over 4 weeks there was a progressive reduction in the area and intensity of local pain and a reciprocal increase in the expression of referred pain. We conclude that the decrease in perceived local pain and increase in perceived referred pain reflects plastic processes occurring centrally. ⋯ What happens to the intensity of pain induced by repeated noxious stimuli over time? Does it stay the same, increase or decrease? Here we show that weekly injections of hypertonic saline into the tibialis anterior cause decreases in local but increases in referred pain, suggesting central changes in processing noxious inputs.
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Studies in adults have shown that the effects of pain catastrophizing upon others vary from positive to negative responses. There are no studies, however, on the impact of catastrophizing in children upon responses of others. In addition, little is known about why catastrohpizing varies with both positive and negative responses. Attachment may be one important moderator explaining these variable relationships. The present study in 1,332 school children investigated, by means of child-report questionnaires, the relationships between pain catastrophizing and parental responses to pain, and the moderating role of child attachment. Findings indicated that a child's pain catastrophizing had a small but significant positive contribution in explaining child reports of both positive and negative parental responses to pain. However, this relationship was moderated by child attachment; for less securely attached children, higher levels of catastrophizing were associated with more negative parental responses. On the contrary, for more securely attached children, higher levels of catastrophizing were associated with more positive parental responses. The present findings suggest that child attachment may partially explain the variable results regarding the impact of pain catastrophizing upon others' responses. The findings are discussed in terms of the function of pain catastrophizing in interactional processes between parents and children. ⋯ This study in schoolchildren found preliminary evidence for the moderating impact of child attachment in understanding differential patterns of parental responses related to the child's pain catastrophizing. Further exploration of the mechanisms relating catastrophizing and attachment processes might contribute to a better comprehension of the interpersonal nature of pain catastrophizing.
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The Pain Management Index (PMI) is used to assess pain medication adequacy in black and white chronic pain patients (18-50 years) at referral to tertiary pain care. Using WHO guidelines for pain treatment, PMI was calculated from pain severity and drug analgesic potency. From 183 patients recruited, 128 provided treatment information for analyses (53% white, 60% female). Most (51.6%) had adequate PMI. Blacks were prescribed fewer pain medications (P = .03); fewer women had adequate medication strength (P = .04). In hierarchical regression, PMI was predicted at entry by female gender, lower MPI, higher affective MPQ, and a gender X age interaction. Younger men experienced better pain management, reducing toward the PMI level of women by age 50. In the final block, black race, being married, affective pain, and gender X age were associated with higher PMI, female gender and being employed were associated with lower PMI. Women, particularly younger women, were at higher risk for inadequate pain management in a primary care environment. These results support variability in chronic pain care and the need for research focusing on whether these disparities persist with specialized pain care. ⋯ Most people with pain receive initial care in a primary care setting. This study examining the adequacy of pain management prior to specialty pain care showed blacks and women had less adequate pain care at referral. These results suggest the need for interventions and education in the primary care arena to improve pain care.
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Since returning from the Persian Gulf, nearly 100,000 veterans of the first Gulf War (GVs) have reported numerous symptoms with no apparent medical explanation. A primary complaint of these individuals is chronic musculoskeletal pain (CMP). CMP symptoms in GVs are similar to those reported by patients with fibromyalgia (FM), but have not received equivalent scientific attention. Exercise research in CMP patients suggests that acute exercise may exacerbate pain while chronic exercise can reduce pain and improve other symptoms. However, the influence of exercise on GVs with CMP is largely unexplored. This study examined the impact of an acute bout of exercise on pain sensitivity in GVs with CMP. Thirty-two GVs (CMP, n = 15; Control, n = 17) were recruited to complete a series of psychophysical assessments to determine pain sensitivity to heat and pressure stimuli before and after exercise. In response to heat-pain stimuli, GVs with CMP reported higher pain intensity and affect ratings than healthy GVs and exhibited a significant increase in ratings following exercise. GVs with CMP rated exercise as more painful and effortful and were generally more sensitive to heat-pain stimuli than healthy GVs. These results are similar to what has been reported for acute exercise in patients with FM. ⋯ Gulf War veterans with CMP perceive exercise as more painful and effortful than healthy GVs and experience increased pain sensitivity following exercise. These results suggest that similar abnormalities in central nervous system processing of nociceptive information documented in FM may also be occurring in GVs with CMP.
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We have previously established a thrombus-induced ischemic pain (TIIP) model in the rat, which mimics the pathophysiology of ischemic pain in patients with peripheral arterial disease. Because ischemia commonly induces acidosis and ATP release, one of the goals of this study was to investigate the role of acid-sensing ion channels (ASICs), transient receptor potential vanilloid-1 (TRPV1) receptors, and P2X receptors in the maintenance of ischemia-induced mechanical allodynia (MA). To test this, amiloride (an ASIC blocker), AMG-9810 (a TRPV1 blocker), or PPADS (a P2Xs antagonist) was intraplantarly injected at day 3 after FeCl(2) application onto the femoral artery. Ipsilateral administration of amiloride or PPADS but not AMG-9810 dose-dependently reduced MA. However, contralateral amiloride or PPADS did not suppress contralateral MA. Interestingly, co-administration of submaximal doses of amiloride and PPADS produced a significantly prolonged suppression of MA. Furthermore, ipsilateral EGTA (a calcium chelator) or chelerythrine (a protein kinase C inhibitor) also significantly reduced MA. Collectively, these findings suggest that peripheral ASICs and P2X receptors are involved in the maintenance of TIIP, which is possibly mediated by a Ca(2+)-protein kinase C signaling mechanism. These results provide mechanistic information about peripheral ischemic nociception that may be useful for developing better therapeutic management of ischemic pain in patients with peripheral arterial disease. ⋯ The results of the current study demonstrate that peripheral administration of an ASICs blocker or P2X antagonist significantly suppress TIIP. Co-administration of submaximal doses of ASIC and P2X antagonists produced an even greater effect. These results implicate peripheral ASICs and P2X receptors in the maintenance of thrombus-induced ischemic pain.