Pain
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Comparative Study Clinical Trial
Postoperative pain assessment and management in adolescents.
A 3-year study investigated the experience and management of postoperative pain following elective surgery in an adolescent sample, using a variety of valid, reliable instruments and semi-structured interviews. In addition to the adolescent subjects, the views of one parent of each adolescent were sought and a sample of health professionals comprising surgeons, anaesthetists and nurses were interviewed about acute pain in adolescent patients. ⋯ Pain, experienced by most adolescents on the 1st and 3rd postoperative days, was influenced by the presence of anxiety and depression, in addition to the maturational stage; differences between in-patients and day cases are highlighted. Recommendations for practice include the need for more effective pain management and raising awareness of the importance of both psychological state and adjustment to adolescence in this age-group.
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The systemic administration of anti-nerve growth factor (NGF) antibodies can prevent local sensory hypersensitivity and block nociceptive fibers from sprouting into denervated adult rat skin. However, in the case of chronic constriction injury (CCI) in a rat, there is evidence that NGF reverses some effects of axotomy and alleviates thermal hyperalgesia. It is with this in mind that we investigated the influence of local anti-NGF and NGF on neuropathic pain and collateral sprouting caused by CCI. ⋯ The results show that the effect of anti-NGF is delayed at the onset, is short in duration, and is dependent on the dosage. However, anti-NGF but not NGF blocked collateral sprouting and decreased the severity of autotomy, suggesting that anti-NGF may be a better potential alternative analgesic for the treatment of neuropathic pain in humans. The different initiation times to abolish thermal hyperalgesia by anti-NGF (delayed onset) and NGF (early onset) suggests that alterations in neurotrophic factors contribute to the development of behavioral hyperalgesia via a complex mechanism in CCI rats.
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Randomized Controlled Trial Clinical Trial
Spatial and temporal summation of sensory and affective dimensions of deep somatic pain.
There is considerable evidence in support of differential information processing of the sensory-discriminative and motivational-affective meanings of pain. The purpose of this work was to examine whether temporal (acute, tonic, persistent) and spatial (local, regional, widespread) aspects of deep somatic pain influence the sensory and affective dimensions of pain. Acute pain consisted of a short bout of pain, lasting about 100 s. ⋯ Affective scores showed the most significant increases from acute to tonic pain, particularly with greater spatial involvement. The significant increases in sensory scores observed when contrasting persistent facial pain alone and in combination with widespread musculoskeletal pain was attributed to the broader body experience. Because the perceptual correlates of tonic and matched persistent (chronic) pain states were similar, we concluded that it does not require months for the development of the sensory and affective meaning of persistent pain as assumed.
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Tactile allodynia and thermal hyperalgesia, two robust signs of neuropathic pain associated with experimental nerve injury, have been hypothesized to be mechanistically distinguished based on (a) fiber types which may be involved in the afferent input, (b) participation of spinal and supraspinal circuitry in these responses, and (c) sensitivity of these endpoints to pharmacological agents. Here, the possibility that nerve-injury induced tactile allodynia and thermal hyperalgesia may be mediated via different afferent fiber input was tested by evaluating these responses in sham-operated or nerve-injured (L5/L6) rats before or after a single systemic injection of resiniferatoxin (RTX), an ultrapotent analogue of the C-fiber specific neurotoxin, capsaicin. Tactile allodynia, and three measures of thermal nociception, tail-flick, paw-flick and hot-plate responses, were determined before and at various intervals for at least 40 days after RTX injection. ⋯ The hypothesis that tactile allodynia may be due to inputs from large (i.e. A beta) afferents offers a mechanistic basis for the observed insensitivity of this endpoint to intrathecal morphine in this nerve-injury model. Further, these data suggest that clinical treatment of neuropathic pains with C-fiber specific agents such as capsaicin are unlikely to offer significant therapeutic benefit against mechanical allodynia.
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The development of alpha-adrenergic sensitivity in cutaneous nociceptors has been postulated as a mechanism for sympathetically maintained pain (SMP). In order to characterize the adrenergic receptors involved, we investigated the effects of intraplantar administration of alpha1-(prazosin) and alpha2-(yohimbine) adrenergic antagonists and systemic injection of phentolamine, a non-specific alpha-adrenergic blocker, on allodynic/hyperalgesic behavior in an animal model thought to mimic SMP in humans. Peripheral neuropathy in rats was induced by tight ligation of the L5/L6 spinal nerves. ⋯ Intradermal administration of yohimbine or prazosin did not significantly alleviate mechanical hyperalgesia in L5/L6 ligated animals. Also systemic administration of phentolamine (1 and 5 mg/kg) did not alleviate the increased incidence of paw withdrawal in L5/L6 spinal nerve ligated animals. These results suggest that an alpha adrenergic interaction between sympathetic efferent and somatic afferent fibers does not play a critical role for the maintenance of mechanical hyperalgesia in this model for neuropathic pain.