The journal of pain : official journal of the American Pain Society
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Repetitive transcranial magnetic stimulation (rTMS) is an emerging technology that has been demonstrated to be useful in the treatment of depression and potentially useful in the management of several neurologic conditions. More recently, increasing attention has been directed at evaluating its efficacy in the treatment of patients with chronic neuropathic pain. We first discuss the literature examining the efficacy of rTMS in trials of experimentally induced acute pain as well as among patients with chronic pain. Examining frequency data obtained from the available literature, we attempted to identify some of the parameters of rTMS that appear to be related to its analgesic effects. An overview of the mechanisms underlying its potential analgesic role is discussed; generally, the influences of rTMS on cortical, and, indirectly, subcortical, neurons may reduce pain transmission ascending from spinothalamic tracts, thereby mitigating pain. Finally, we discuss some of the methodological issues and limitations of available studies and offer recommendations for further research. ⋯ The authors provide a comprehensive review of rTMS use in the treatment of neuropathic pain in the literature available to date. Although the clinical usefulness of rTMS in pain has, as yet, to be determined, it offers insights into the pathophysiologic processes involved in the maintenance and exacerbation of chronic pain.
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In children with advanced stages of cancer, pain control remains inadequate in many patients and a solution to this problem is sorely lacking. Factors related to progression of the primary disease and side-effects of high doses of opioids, the mainstay of pain therapy, contribute to the inadequacy of pain control. In addition, few studies suggest that opioids, by inducing tolerance, having pronociceptive effects and producing hyperalgesia in some patients, can also contribute to inadequacy of pain control. Researchers have shown that N-methyl-D-aspartate (NMDA) receptor antagonists may have a role in mitigating opioid-induced tolerance and hyperalgesia in adults. However, literature on NMDA antagonists to treat cancer pain in children and adolescents is scarce. We used subanesthetic doses of ketamine to treat 11 children and adolescents who were on high doses of opioids and yet had uncontrolled cancer pain. A low-dose ketamine infusion was administered to all patients to modulate the need for rapidly escalating opioid therapy. We found that in 8 of 11 patients, ketamine infusions used as an adjuvant to opioid analgesia was associated with opioid-sparing effects and apparent improvement in pain control and in the children's ability to interact with their family. This study suggests that infusions of ketamine may offer a promising therapeutic option in the treatment of appropriately selected children and adolescents with intractable cancer pain. ⋯ In many children with advanced stages of cancer, pain control remains inadequate. We used subanesthetic doses of ketamine to treat 11 children and adolescents who were on high doses of opioids and had uncontrolled cancer pain. In the majority of patients, ketamine appeared to improve pain control and to have an opioid-sparing effect.
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The aim of this study was to investigate local opioid effects in the inflamed skin of healthy human volunteers. To induce inflammation, the circular tip of a 10-mm-diameter probe was heated to 48 degrees C and applied for 120 seconds to a site on each forearm of 24 healthy participants. Thirty minutes later, 0.2 mL of normal saline was injected subcutaneously into 1 inflamed site, and the opioid antagonist naloxone hydrochloride (80 microg in 0.2 mL) was injected subcutaneously into the other inflamed site. Participants completed tests of pain sensitivity (heat pain thresholds, heat pain ratings, and mechanical pain ratings) before and after the injections. Fentanyl citrate (10 microg in 0.2 mL) was then injected into the pretreated sites, and pain sensitivity was measured again. The thermal injuries produced thermal and mechanical hyperalgesia that did not differ between the saline and naloxone sites. After the fentanyl injections, decreases in thermal and mechanical hyperalgesia were greater at the saline site than the naloxone site. These findings demonstrate that pretreatment with naloxone blocks local opioid effects produced by the subcutaneous injection of a low dose of fentanyl in the inflamed skin of healthy humans. Thus, peripheral opioid receptors could be a therapeutic target for painful cutaneous disorders. ⋯ This article demonstrates that activation of opioid receptors in the skin inhibits sensitivity to painful mechanical and thermal stimuli. Thus, local application of low-dose opioid medications could relieve painful skin disorders.
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Intradermal capsaicin injection (CAP) and electrical current stimulation (ES) are analyzed in respect to patterns and test-retest reliability of pain as well as sensory and neurosecretory changes. In 10 healthy subjects, 2x CAP (50 microg) and 2x ES (5 to 30 mA) were applied to the volar forearm. The time period between 2 identical stimulations was about 4 months. Pain ratings, areas of mechanical hyperalgesia, and allodynia were assessed. The intensity of sensory changes was quantified by using quantitative sensory testing. Neurogenic flare was assessed by using laser Doppler imaging. Calcitonin gene-related peptide (CGRP) release was quantified by dermal microdialysis in combination with an enzyme immunoassay. Time course and peak pain ratings were different between CAP and ES. Test-retest correlation was high (r > or = 0.73). Both models induced primary heat hyperalgesia and primary plus secondary pin-prick hyperalgesia. Allodynia occurred in about half of the subjects. Maximum flare sizes did not differ between CAP and ES, but flare intensities were higher for ES. Test-retest correlation was higher for flare sizes than for flare intensity. A significant CGRP release could only be measured after CAP. The different time courses of pain stimulation (CAP: rapidly decaying pain versus ES: pain plateau) led to different peripheral neurosecretory effects but induced similar central plasticity and hyperalgesia. ⋯ The present study gives a detailed overview of psychophysical and neurosecretory characteristics induced by noxious stimulation with capsaicin and electrical current. We describe differences, similarities, and reproducibility of these human pain models. These data might help to interpret past and future results of human pain studies using experimental pain.
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Multicenter Study
Pain in the emergency department: results of the pain and emergency medicine initiative (PEMI) multicenter study.
Pain is the most common reason for emergency department (ED) use, and oligoanalgesia in this setting is known to be common. The Joint Commission on Accreditation of Healthcare Organizations has revised standards for pain management; however, the impact of these regulatory changes on ED pain management practice is unknown. This prospective, multicenter study assessed the current state of ED pain management practice. After informed consent, patients aged 8 years and older with presenting pain intensity scores of 4 or greater on an 11-point numerical rating scale completed structured interviews, and their medical records were abstracted. Eight hundred forty-two patients at 20 US and Canadian hospitals participated. On arrival, pain intensity was severe (median, 8/10). Pain assessments were noted in 83% of cases; however, reassessments were uncommon. Only 60% of patients received analgesics that were administered after lengthy delays (median, 90 minutes; range, 0 to 962 minutes), and 74% of patients were discharged in moderate to severe pain. Of patients not receiving analgesics, 42% desired them; however, only 31% of these patients voiced such requests. We conclude that ED pain intensity is high, analgesics are underutilized, and delays to treatment are common. Despite efforts to improve pain management practice, oligoanalgesia remains a problem for emergency medicine. ⋯ Despite the frequency of pain in the emergency department, few studies have examined this phenomenon. This study documents high pain intensity and suboptimal pain management practices in a large multicenter ED network in the United States and Canada. These findings suggest that there is much room for improvement in this area.