Pain
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Psychophysical experiments were carried out on 7 human participants to determine the extent to which experimentally produced first or second pain is reduced by concomitant nociceptive stimulation of body regions remote from those at which test stimuli are presented. This form of pain reduction has been termed diffuse noxious inhibitory controls (DNIC). Test stimuli used to evoke first and second pain consisted of intense electrical pulses delivered to the ankle area by subepithelial electrodes. ⋯ All of these results closely parallel electrophysiological observations about DNIC in primates. Since the extent of reduction of first pain is relatively weak and the durations of all inhibitory effects are very brief, it is unlikely that DNIC subserves the functions of relieving pain or providing a mechanism of coding pain. The spatial and temporal pattern of DNIC indicates that it may be a phenomenon associated more with the organization and production of withdrawal reflexes than with the relief of pain or pain coding.
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Pain responses (threshold, tolerance, and visual analog ratings) to the cold pressor task were studied in 46 normally menstruating dysmenorrheic and non-dysmenorrheic women during 2 phases of the menstrual cycle. Twenty-six women provided measurements during the follicular (days 8-14) and 20 during the luteal (days 15-21) phases of the menstrual cycle. A significantly lower pain threshold was obtained during the luteal as compared to the follicular phase. ⋯ Visual analog ratings were significantly lower in dysmenorrheic women during the follicular than the luteal phase. Also, these ratings were lower than those of non-dysmenorrheic women in the follicular phase. This finding may support an adaptation-levels model, in that dysmenorrheic women report less pain than do non-dysmenorrheic women because they compare cold pressor pain with internal menstrual pain.
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Randomized Controlled Trial Clinical Trial
A double-blind comparison between epidural morphine and epidural clonidine in patients with chronic non-cancer pain.
In a randomised double-blind study of 20 patients with chronic pain, epidural morphine 5 mg in 5 ml of saline was compared with epidural clonidine 150 micrograms in 5 ml of saline. Thirteen patients had a clinical and radiological diagnosis of arachnoiditis, 6 had low back pain and 1 had post-operative scar pain. There were 18 females and 2 males with an average age of 52 years, range 22-76 years. ⋯ Clonidine was associated with sedation and a fall in blood pressure of greater than 20 mm Hg in all patients, 1 patient required ephedrine to treat hypotension. Twelve patients had pruritus, 7 nausea and 2 vomiting following the morphine. Statistically there was no difference found between morphine and clonidine for short-term (3 h) analgesia in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)
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Comparative Study Clinical Trial Controlled Clinical Trial
Morphine and ibuprofen compared using the cold pressor test.
The analgesic efficacy of single doses of oral morphine sulphate solution (10 mg) and ibuprofen 600 mg was compared in 12 volunteers using a double-blind, double-dummy, placebo-controlled design on the cold pressor experimental pain model. Measurement of pain intensity was made before medication and then at 30, 60, 90, 120 and 180 min; blood samples were taken at these times for measurement of morphine and glucuronide metabolites by radioimmunoassay. Sessions were at least 5 days apart. ⋯ Ibuprofen was statistically indistinguishable from placebo on all three measures of analgesia. Analgesic effect and plasma concentrations of morphine showed significant correlation (P = 0.053). The study confirmed reports of the opiate sensitivity of the cold pressor model, and the apparent insensitivity of the model to non-steroidal anti-inflammatory drugs.
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According to myogenic models that relate abnormal EMG patterns to the experience of pain, lumbar paravertebral muscle activity has been considered to play an important role in chronic low back pain. In the present study, 40 chronic low back pain patients and 40 matched non-patient controls were compared on lumbar paravertebral EMG during mechanically stabilized static and dynamic postures. ⋯ In addition, most patients did not show the flexion-relaxation response or the expected pattern of EMG responses during trunk rotation, most likely because of restricted range of motion and/or compensatory posturing. These findings provide support for the biomechanical model of chronic pain and indicate the need for further research pertaining to pain behavior and movement-related lumbar muscle activity.