Pain
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Experimental C-fiber pain caused by radiant heat was applied to the skin area supplied by the left sural nerve of 20 subjects. Percutaneous electrical stimulation (PNS) was performed on the left sural nerve, the left superficial peroneal nerve and the right superficial radial nerve. Stimulation frequencies were: 3, 50, 100, 300, 500 and 1000 Hz. ⋯ Without considering the influence of the different frequencies, the best analgesic effects were reached if noxious heating and PNS were both performed on the left sural nerve; the anatomical conditions prevented us from distinguishing between the effects of possible peripheral blockade or spinal modification of pain. PNS of the superficial peroneal nerve seems to indicate spinal, possibly polysegmental, interactions between C-fiber pain and electrical stimulation of thick myelinated fibers. However, long loop effects may also play a part in local analgesia as demonstrated by PNS of the right radial nerve.
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Transcutaneous electrical nerve stimulation and the reaction to experimental pain in human subjects.
The effect of peripheral transcutaneous electrical nerve stimulation (TENS) on the reaction to experimental pain in human volunteers has been assessed. Placebo stimulation and electrical stimulation at moderate intensities failed to modify the response to the pain produced by conducted thermal stimuli. ⋯ The subjective pain assessment and the maximum pain tolerance produced by ischaemic pain after a submaximal effort tourniquet test were significantly modified by peripheral electrical stimulation at non-noxious intensities. The response to experimental pain can therefore be altered in man by peripheral electrical stimulation in a manner partly dependent on the sensory modality used for producing the experimental pain and on the intensity of the electrical stimulation.
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An evaluation of acupuncture for pain relief was made in 10 patients with sickle cell anaemia during 16 pain crises. A model was developed in which the patient served as his own control and in which both patient and examiner were unaware of whether an acupuncture point or a sham site was treated. The results show (1) that pain relief was obtained in 15 of the 16 painful episodes regardless of whether an acupuncture point or a sham site was treated, demonstrating considerable overlap between the effects of needling acupuncture points and sham sites; (2) that needling at acupuncture points for pain relief is not significantly superior to treatment at sham sites; (3) that needling, per se, whether at acupuncture points of at sham sites can be useful for alleviating pain in sickle cell crises. The model could be useful for evaluation of pain relief by needling in other diseases.
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The submaximum effort tourniquet technique (SETT) is becoming more widely used as part of the clinical assessment of chronic pain patients despite little information about the scaling of this technique. Ratio scaling procedures resulted in a linear function, presumed to underlie clinical application of the SETT, for only 11% of the subjects. ⋯ Differences in these growth curves are discussed with reference to the concept of pain endurance. Continued needs for standardized pain evaluation techniques suggest that this type of psychophysical scaling procedure may improve the precision of some clinical pain assessments.
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The submaximal effort tourniquet test has been widely used to evaluate experimental and chronic pain; however, there has been great variation in the manner in which the test has been applied. The present study systemitically evaluates how different levels of exercise duration and effort affect subjects' report of pain. The data indicate the following: (1) the manner in which the exercise is performed has an important effect on subjects' rating of pain, and (2) under all conditions studied, the pain ratings do not increase as a linear function of time. Both findings warrant precautions when using the submaximal effort tourniquet test to study experimental and chronic pain.