Pain
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Randomized Controlled Trial Clinical Trial
Epidural clonidine analgesia for intractable cancer pain. The Epidural Clonidine Study Group.
Although the vast majority of patients with cancer pain receive effective analgesia from standard therapy, a few patients, particularly those with neuropathic pain, continue to experience severe pain despite large doses of systemic or intraspinal opioids. Animal studies suggest intraspinal alpha 2-adrenergic agonists may be effective in such cases. Eighty-five patients with severe cancer pain despite large doses of opioids or with therapy-limiting side effects from opioids were randomized to receive, in a double-blind manner, 30 micrograms/h epidural clonidine or placebo for 14 days, together with rescue epidural morphine. ⋯ Clonidine, but not placebo, decreased blood pressure and heart rate. Hypotension was considered a serious complication in 2 patients receiving clonidine and in 1 patient receiving placebo. This study confirms the findings from previous animal studies which showed the effective, potent analgesic properties of intraspinal alpha 2-adrenergic agonists and suggests that epidural clonidine may provide effective relief for intractable cancer pain, particular of the neuropathic type.
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Clinical Trial Controlled Clinical Trial
Modulation of pressure pain thresholds during and following isometric contraction.
This study aimed at evaluating the influence of submaximal isometric contraction on pressure pain thresholds (PPTs) in 14 healthy volunteers before and after skin hypoesthesia. PPTs were determined with pressure algometry over m. quadriceps femoris before, during, and following an isometric contraction. Maximum voluntary contraction (MVC) was assessed using a computerized dynamometer. ⋯ Isometric contraction of m. quadriceps femoris increase PPTs during and following contraction. The results suggest that input from cutaneous and deeper tissues interacts with nociceptive activity set up by the pressure stimulus. Determining the degree of sensory modulation in muscle and skin in different chronic pain syndromes could become a functional method of patient assessment important for differential diagnosis, treatment evaluation, and follow-up.
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Clinical Trial Controlled Clinical Trial
Differential response to pain by very premature neonates.
The ability of very low birth weight (VLBW) premature infants to respond differentially to real versus a sham heelstick conditions was examined in this crossover study. Using a multidimensional assessment of responses of premature infants (n = 48) between 26 and 31 weeks gestational age (GA) at the time of the study, it was found that they respond differentially to real versus sham heelstick both behaviourally and physiologically. The multivariate effect of condition (real/sham) was significant with maximum heart rate and upper facial action (lower facial action was not scored) contributing significantly to the main effect. ⋯ The variability outcome measures of heart rate standard deviation and range of transfontanelle intracranial pressure contributed significantly to the main effect of GA, but not to the effect of condition. Young VLBW premature infants are capable of a multidimensional differential response to pain. GA is an important factor to consider when assessing pain in premature infants.
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Comparative Study
Gender differences in pain ratings and pupil reactions to painful pressure stimuli.
In order to investigate gender differences in pain perception, the present study employed both a psychophysical and a psychophysiological measure. In experiment 1, 20 subjects rated the painfulness of 4 different levels of tonic pressure applied to their fingers using a verbally anchored categorization procedure. In general agreement with studies of pain threshold and tolerance, female subjects reported greater pain at high levels of stimulation, with no gender difference being evident at low pressure levels. ⋯ The pupil dilations seen during the last 10 sec of the 20-sec pressure application turned out to be a highly significant indicator of pain intensity. When female and male subjects were compared on this measure, a similar divergent pattern as in the psychophysical data emerged, with female subjects showing greater pupil dilations at high pressure levels only. The fact that gender differences in pain perception can be demonstrated using an autonomic indicator of pain that is beyond voluntary control suggests that these differences reflect low-level sensory and/or affective components of pain rather than attitudinal or response-bias factors.
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Primary C-fiber afferents can induce a state of increased excitability in spinal cord neurons amplifying their responsiveness to noxious and innocuous stimuli--the phenomenon of central sensitization. We have examined whether the hypersensitivity to low-intensity stimuli (mechanical allodynia) evoked by C-afferent conditioning inputs is NMDA receptor dependent. The enhancement by C-afferent conditioning stimuli of the normally low or absent cutaneous touch-evoked responses of posterior biceps femoris/semitendinosus flexor motoneurons in the decerebrate-spinal rat has been used as a model of touch-evoked allodynia. ⋯ Treatment with MK 801 some time after the conditioning input when the mechanical hypersensitivity is fully established, also reduced the increased touch-evoked responses. The reduction in threshold and the increase in touch responsiveness induced by cutaneous and muscle noxious C-fiber conditioning stimuli in the rat spinal cord are, therefore, both prevented and reversed by NMDA receptor antagonism. NMDA antagonists may be potentially useful, therefore, in treating postinjury pain hypersensitivity.