The journal of pain : official journal of the American Pain Society
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To examine the role of nerve growth factor (NGF) in postoperative pain, we administered the tyrosine kinase A (Trk A) immunoglobulin G (IgG) fusion (1 to 10 mg/kg) molecule before and after plantar incision. We also pretreated rats with a tumor necrosis factor receptor (TNFr) protein, p75 IgG fusion protein (5 to 10 mg/kg), to study the role of endogenous TNF in the development of pain behaviors after incision. Rats underwent a plantar incision, and responses to punctate and nonpunctate mechanical stimuli and withdrawal latency to radiant heat were measured. Rats were tested on the day of incision and daily for 4 days. Reduced withdrawal latency to radiant heat occurred after incision in the control group treated with IgG. Both pretreatment and treatment after incision with 5 mg/kg dose of Trk A IgG fusion protein increased the withdrawal latency to heat in incised rats (P <.05) through 4 days. A similar effect was observed after 10 mg/kg was administered after incision. Neither dose influenced the reduced withdrawal threshold and increased response to blunt mechanical stimulation caused by the incision. Pretreatment with 5 or 10 mg/kg of TNFr IgG fusion protein had no effect on any of the incision-induced pain-related behaviors. We conclude that sequestration of NGF affected responses to heat after incision but did not influence responses to mechanical stimuli. Thus, fibers sensitive to heat are influenced by NGF and probably do not contribute to exaggerated responses to mechanical stimuli. TNF does not appear to have a role in the pain behaviors. ⋯ To treat postoperative pain better, we should discover the factors that are causing incisional pain. One endogenous factor that contributes to pain after incision is NGF. Inhibition of NGF may provide a new way to treat pain after surgery with minimal side effects. This could improve outcome after surgery.
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Racial and ethnic minorities, older people, and women are differentially affected by chronic pain. This study aimed to identify the experiences of adult African Americans and whites with chronic pain while identifying patient clusters on the basis of clinical characteristics as well as race, age, and gender influences within and between clusters. Three clusters of patients with chronic pain were identified within race, age, and gender categories: chronic pain syndrome, good pain control, and disability with mild syndrome. African American and younger patients experiencing chronic pain were more likely to present with chronic pain syndrome. African American patients presenting with chronic pain syndrome or disability with mild pain syndrome reported a higher disability than their counterparts. Older patients and women within the good pain control cluster reported a lower level of (1) pain and depression and (2) depression, respectively. Older patients presenting with a disability with mild syndrome also reported lower pain and depression. Despite similar physical, emotional, and pain characteristics, this study confirmed that the chronic pain experience differs across racial and age groups. Further study is necessary to evaluate how these factors influence pain services among an ethnically diverse population across the age continuum. ⋯ This study found important racial and age-related variability in the symptom severity of patients with chronic pain presenting with similar physical, emotional, and pain characteristics to a tertiary care pain center. These findings have important clinical implications on chronic pain assessment and management.
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The Brief Pain Inventory (BPI; Cleeland and associates) has been used primarily to assess patients with cancer-related pain. Although it has been validated in many languages and is widely used, there has not yet been research published to validate its use for patients with chronic nonmalignant pain as the primary presenting problem. This study was designed to fill this gap by examining the psychometric properties of the BPI in 440 patients with chronic intractable pain referred to a chronic pain clinic at a metropolitan tertiary-care teaching hospital. Results indicated acceptable internal consistency (Cronbach alpha coefficients were.85 for the intensity items and.88 for the interference items). A factor analysis resulted in 2 distinct and independent factors, supporting the validity of the 2-factor structure of the BPI. Zero-order correlations indicated that the association with a measure of disability (the Roland-Morris Disability Questionnaire [RMDQ]) was significantly higher for BPI interference (r = 0.57) than for BPI intensity (r = 0.40, t = 5.71, P <.01) and that the correlation with BPI interference was not more than 0.80, supporting the conclusion that these scales assess related, but also distinct, dimensions. Finally, the finding that both BPI scales showed statistically significant improvement with treatment confirms the responsivity of BPI in detecting and reflecting improvement in pain over time. ⋯ This paper validated the psychometric properties of a pain Assessment instrument (The Brief Pain Inventory) originally developed to assess cancer pain and extended its use for the chronic nonmalignant pain population. This provides an important and widely used diagnostic tool for the clinician treating chronic pain.
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Comparative Study
Influences of gender role and anxiety on sex differences in temporal summation of pain.
Previous research has consistently shown moderate to large differences between pain reports of men and women undergoing experimental pain testing. These differences have been shown for a variety of types of stimulation. However, only recently have sex differences been demonstrated for temporal summation of second pain. This study examined sex differences in response to temporal summation of second pain elicited by thermal stimulation of the skin. The relative influences of state anxiety and gender role expectations on temporal summation were investigated. Asymptomatic undergraduates (37 women and 30 men) underwent thermal testing of the thenar surface of the hand in a temporal summation protocol. Our results replicated those of Fillingim et al indicating that women showed increased temporal summation compared to men. We extended those findings to demonstrate that temporal summation is influenced by anxiety and gender role stereotypes about pain responding. When anxiety and gender role stereotypes are taken into account, sex is no longer a significant predictor of temporal summation. These findings highlight the contribution of social learning factors in the differences between sexes' pain perception. ⋯ Results of this study demonstrate that psychosocial variables influence pain mechanisms. Temporal summation was related to gender role expectations of pain and anxiety. These variables explain a significant portion of the differences between men and women's pain processing, and may be related to differences in clinical presentation.
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Clinical Trial
Pain management of cancer patients with transdermal fentanyl: a study of 1828 step I, II, & III transfers.
The aim of this observational study was to examine pain management outcomes and quality of life (QoL) measures in cancer patients with intolerable or chronic severe pain transferring from World Health Organization's step I, II, and III analgesics to the transdermal therapeutic fentanyl system (TTS-F). This study examines the safety and efficacy of TTS-F in long-term pain management, addressing the role of TTS-F in cancer pain. Pain measures were assessed in 1828 patients (step I [naïve], 268; step II [codeine], 1239; and step III [morphine], 321) on the basis of selected questions from the Greek-Brief Pain Inventory. Overall treatment satisfaction (scale, 1 to 4), QoL, and European Collaborative Oncology Group (ECOG) status were also recorded. These were assessed in relation to TTS-F dose, stratified by transfer step, primary cancer, metastases, type of pain, and concomitant use of anti-inflammatory drugs. Of 1828 patients, 100 (5.5%) withdrew, and an addition 14 (0.8%) discontinued because of side effects. A total of 1714 continued on study; 744 patients died, and 970 departed during the study period. In total, 93.8% were satisfied with their pain relief, and complete patient satisfaction was obtained within 2 months. Pain, QoL, and treatment satisfaction measures demonstrated statistically significant improvements over time, independent of the step transfer. Although doses of TTS-F were higher for step III > II > I and for metastatic than nonmetastatic, the median dose for all groups remained 50 microg/h throughout the study period. Pain and QoL improvements were independent of patient characteristic(s). Direct transfer to TTS-F for patients with intolerable or chronic moderate to severe cancer pain offers an efficient and safe long-term analgesic option for palliative care patients. Careful selection and follow-up by experienced palliative care specialists are mandatory. TTS-F as a first-line analgesic approach for severe cancer pain should be considered a viable option because of its durable efficacy and low incidences of side effects. ⋯ At a fairly constant dose of 50 microg/h, the transdermal therapeutic fentanyl system offers a safe, well-tolerated pain relief treatment for carefully monitored patients with cancer pain. The authors stress that this includes patients who experience difficulties in their pain management while progressing through the WHO's ladder for pain management.