Pain
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Clinical Trial Controlled Clinical Trial
Comparison of ketamine and pethidine in experimental and postoperative pain.
The analgesic efficiency of ketamine and pethidine was compared in experimental ischemic pain and postoperative pain after oral surgery. Naloxone 1.6 mg or placebo was given 5 min before the analgesic drug. ⋯ Naloxone prevented the analgesic effect of pethidine, but had no effect on ketamine analgesia. The results are in accordance with the hypothesis that the analgesic effect of ketamine is mediated by a non-opioid mechanism, possibly involving PCP-receptor-mediated blockade of the NMDA-receptor-operated ion channel.
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Pain and thermal sensitivity thresholds in healthy volunteers were examined for diurnal variations. The subjects were 11 men aged between 22 and 27 years (means = 23.5, S. D. = 1.5). ⋯ However, they could not be demonstrated for the thermal sensitivity measures. The diurnal variations in pain perception thresholds did not have a consistent pattern over all subjects (Friedman test). The small diurnal variations with interindividual differences in the pattern are therefore not sufficient to explain the variations seen in clinical pain, but they may be useful in detecting pain modulators by investigating correlations.
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This study tested the hypothesis that distraction from a painful stimulus is best achieved by concurrent presentation of a similar stimulus. Specifically, it was hypothesized that pain perception would be interfered with, and thus reduced, when a stimulus similar to the sensory features of a painful stimulus was delivered concurrently. Subjects matched aversiveness thresholds for electrocutaneous or auditory stimulation so that both forms of stimulation could be judged to be subjectively of similar affective value. ⋯ Magnitude estimation ratings of the aversiveness of counterstimulation were provided concurrently with cold pressor pain ratings, every 30 sec. The results indicated that, as predicted, subjects exposed to concurrent electrical stimulation produced lower pain ratings than subjects exposed to auditory stimulation and controls. In addition, a mutual interference effect between the cold pressor and the tactile counterstimulation was found: subjects also rated electrical stimulation as a less aversive than auditory stimulation over the duration of the cold pressor test.
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Inoculation of the right hind paw with Mycobacterium butyricum rapidly led to swelling and inflammation. The afflicted limb showed an enhanced sensitivity to noxious pressure (hyperalgesia) and a reduced sensitivity to noxious heat 24 h following treatment. Both naloxone and MR 2266 (which has greater activity at kappa-opioid receptors) further increased the sensitivity to pressure (that is, potentiated the hyperalgesia) but did not affect the response to heat. ⋯ The effect is specific to DYN as compared to ME and LE. The density of mu-, delta-, or kappa-receptors in the lumbar spinal cord is unmodified. (2) The altered response to opioid agonists and antagonists shown by rats with an inflamed limb may be selective to the injured tissue. (3) Alterations in opioid systems associated with unilateral hind limb inflammation may not be exclusively chronic in nature: they appear very rapidly (within 24 h) of the induction of pain. With time, the contralateral limb becomes affected and, eventually, the effects resemble those seen with generalized polyarthritis.
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The Descriptor Differential Scale (DDS) applies psychophysical principles to clinical pain assessment. It contains 12 descriptor items for each pain dimension assessed. For each item, subjects indicate if their pain either is equal in magnitude to that implied by the anchoring descriptor, or how much greater or lesser on a 10-point graphic scale. ⋯ Ninety-one patients completed the sensory intensity and unpleasantness forms of the DDS at both 1 and 2 h after surgical extraction of a lower third molar. Results show that the DDS satisfies standard psychometric criteria for reliability, objectivity and item homogeneity. The coefficients found satisfy standard psychometric criteria and improve after elimination of inconsistent profiles.