Pain
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Randomized Controlled Trial Clinical Trial
The efficacy of hypnosis- and relaxation-induced analgesia on two dimensions of pain for cold pressor and electrical tooth pulp stimulation.
This study evaluated the efficacy of hypnosis- and relaxation-induced suggestions for analgesia for reducing the strength and unpleasantness dimensions of pain evoked by noxious tooth pulp stimulation and by cold pressor stimulation. The Tellegen Absorption Questionnaire was used to assess hypnotic susceptibility for 28 subjects in order to match treatment groups according to sex and susceptibility scores. Tooth pulp stimulation consisted of a 1 sec train of 1 msec pulses at a frequency of 100 Hz, applied at 20 sec intervals to the central incisor. ⋯ Tooth pulp and cold pressor stimulation represent qualitatively different stimuli with respect to both the type of nerves activated and the mode of stimulus application. Discrete, randomly presented levels of noxious electrical stimulation to the teeth activate predominantly small fibers and produce brief pain sensations that vary unpredictably in intensity. In contrast, continuous cold stimulation to the forearm activates a variety of nociceptive and non-nociceptive fibers and produces progressive cold and pain sensations with a predictable increase in intensity from cold sensations to paresthesia and severe pain.
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Randomized Controlled Trial Clinical Trial
Regional sympathetic blockade in primary fibromyalgia.
Twenty-eight patients with primary fibromyalgia participated in the study. Eight patients received a stellate ganglion blockade with bupivacaine, and 14 days later an intravenous regional sympathetic blockade with guanethidine. The remaining patients served as controls and were randomly allocated to receive either a sham (placebo) injection with physiologic saline superficial to the stellate ganglion (n = 10) or bupivacaine intramuscularly (n = 10). ⋯ The guanethidine blockade reduced the number of TePs, but had no effect on rest pain. The reduction in pain and TePs produced by a sympathetic blockade may be due to an improvement in microcirculation. Sympathetic activity may, in some patients, contribute to the pathogenesis of primary fibromyalgia.
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These experiments quantitatively analyzed effects of electrical midbrain stimulation on a nociceptive hind limb flexion reflex in rats anesthetized with sodium pentobarbital. We recorded the force of isometric hind limb flexion withdrawal, and related flexor electromyographic (EMG) activity, elicited by noxious heat (42-54 degrees C, 10 sec) applied to the ventral hind paw. Several hind limb flexors including biceps femoris were active during the reflex. ⋯ Naloxone had little effect, while methysergide and phentolamine reduced PAG- and LRF-evoked reflex suppression in about one-half of the cases. Scopolamine largely reduced PAG- and LRF-evoked reflex suppression (in 8/9 and 4/6 rats, respectively). These results indicate that the flexion reflex is under parametrically but not pharmacologically distinct inhibitory midbrain controls.