Pain
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Randomized Controlled Trial Clinical Trial
Determinants of success and failure of EMLA.
Although EMLA is known to be an effective topical anesthetic, its rate of success is unknown. Indeed, researchers have suggested that EMLA may fail with young and apprehensive children. Therefore, the objectives of this study were to assess EMLA's rate of success as well as factors which predict success. ⋯ Those who had a poor outcome were more anxious than those with a good outcome. Age of child was not a factor. Strategies for improving efficient use of EMLA were recommended.
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Clinical Trial Controlled Clinical Trial
Monitoring adequacy of alpha-adrenoceptor blockade following systemic phentolamine administration.
Systemic phentolamine administration has been suggested as a diagnostic tool for identifying patients with sympathetically maintained pain (SMP) (Raja et al. 1991). The dose of phentolamine to produce adequate blockade of peripheral alpha-adrenoceptor function has, however, not been previously determined. In this study, the effects of two different doses of phentolamine on peripheral sympathetic vasoconstrictor function were investigated. ⋯ However, SMR was not completely attenuated, even after administration of the higher phentolamine dose. These results indicate that a phentolamine dose of 1 mg/kg over 10 min more completely blocks alpha-adrenoceptor function than a dose of 0.5 mg/kg over 20 min. We therefore recommend that to ensure adequate alpha-adrenoceptor blockade the higher phentolamine dose be used in the phentolamine diagnostic test for SMP.
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Although pain assessment is a vital preliminary step towards the satisfactory control of cancer pain, data on the prevalence of different pain syndromes are rare. In a prospective study of 2266 cancer patients, we assessed localisations, aetiologies and pathophysiological mechanisms of the pain syndromes. Thirty percent of the patients presented with 1, 39% with 2 and 31% with 3 or more distinct pain syndromes. ⋯ The main pain syndrome was also coded according to the IASP Classification of Chronic Pain. Regions and systems affected by the main pain syndrome showed large variation depending on the site of cancer origin, whereas temporal characteristics, intensity and aetiology were not markedly influenced by the cancer site. The variety of pain syndromes evaluated in our patients confirms the importance of comprehensive pain assessment prior to treatment.
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This study was conducted to determine the contribution of peripheral inputs from injured and intact afferent fibers to behavioral signs of neuropathic pain, using a previously developed neuropathic rat model. Neuropathic injury was produced by tightly ligating the left L5 and L6 spinal nerves; this procedure induced rats to display neuropathic pain behaviors in the ipsilateral hindlimb. The behaviors included signs of mechanical and cold allodynia, as well as ongoing pain. ⋯ Blocking afferent inputs by application of bupivacaine mimicked the results of dorsal rhizotomy, in a reversible manner. These results suggest that afferent signals from injured and intact fibers play distinctively different roles in neuropathic pain: inputs from injured afferents maintain all components of neuropathic pain, while those from intact afferents mediate evoked pain such as mechanical and cold allodynia. An hypothesis is proposed to explain the results of the present as well as other published studies.
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Comparative Study
Fixed-diameter polyethylene cuffs applied to the rat sciatic nerve induce a painful neuropathy: ultrastructural morphometric analysis of axonal alterations.
Polyethylene cuffs of varying inner diameters were applied to the rat sciatic or sural nerve with the aim of inducing a standardized nerve injury, as assessed by morphometric analyses of fiber-size spectrum alterations, associated with behavioral manifestations of neuropathic pain. The temporal sequence of axonal degeneration and regeneration was examined in parallel with behavioral analyses of pain initiation and recovery over a 6-week postoperative (PO) period. Cuffs of 0.028-0.030" inner diameter loosely enclosed sciatic nerves of young rats and elicited relatively uniform axonal degeneration and 'pain'. ⋯ Consistent behavioral manifestations of pain were achieved over a wide range of fiber spectrum alteration; however, with the largest cuffs or 'bracelets' used in this study, a substantial axonal fiber spectrum change was produced without inducing pain-related behavior, suggesting that decrement in the number of myelinated axons was not always sufficient to elicit pain. Similar morphometric and pathological results were achieved with sural neuropathy after 0.010" ID cuffs and 14 days PO survival. Considering the lack of correlation between axonal alterations and pain, modification in the local intraneurial microenvironment at the site of injury may be a key component of peripheral pain mechanisms; these include changes in the biochemical milieu, increased intraneurial pressure, and altered nociceptor sensitivity or impulse propagation in the relatively intact unmyelinated axon population.