Pain
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The aims of this study were to explore: (a) the interrelation between spatial summation (SS) and spatial discrimination (SD) of pain, (b) whether the two phenomena are subserved by different sensory channels. SS and SD of pain were measured with contact heat stimuli delivered at slow (0.50 degrees C/s) and fast (40 degrees C/s) rise times. Pressure nerve block of the radial nerve was employed to assess whether differential activation of C and A delta fibers is obtained by these different rates of rise. ⋯ Stimulation rate did not affect SS or SD. Following nerve block, thresholds obtained with the fast rise stimulation increased significantly (HPT rose from 46.2 to 50.5 degrees C) but those obtained with slow rise stimuli were not affected by the block, indicating that C and A delta fibers were activated selectively. The results suggest that: (a) SS and SD are mutually exclusive functions of the nociceptive systems, (b) C and A delta nociceptors are probably similarly involved in these functions.
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Randomized Controlled Trial
Differential sensitivity of three experimental pain models in detecting the analgesic effects of transdermal fentanyl and buprenorphine.
This is the first randomized controlled trial that tests the analgesic efficacy of transdermally delivered opioids in healthy volunteers and that assesses the sensitivity of different experimental pain tests to detect analgesia in this setting. Transdermal application of the full agonist fentanyl (TDF: 12.5 or 25 microg/h) and the partial agonist buprenorphine (TDB: 35 microg/h) was compared in three experimental models of acute pain (heat pain, painful electrical stimulation, cold pressor) in a double-blind, randomized, placebo-controlled, 4-arm crossover study with 20 healthy subjects (15 men, 5 women). Patches were administered for 72 h and pain levels measured at baseline and 24 and 72 h, with an 11-day wash-out. ⋯ We conclude that the cold pressor test was most sensitive to analgesic effects in healthy subjects and that a transdermal dose of 12.5 microg/h fentanyl achieved significant pain reduction compared with placebo. Subjects experienced opioid-typical AEs including dizziness, nausea and vomiting. No serious AEs occurred.
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Randomized Controlled Trial
Efficacy and safety of acupuncture for chronic uncomplicated neck pain: a randomised controlled study.
Chronic neck pain is highly prevalent. To determine the efficacy and safety of acupuncture, in comparison with transcutaneous nerve stimulation-placebo (TENS-placebo) in the treatment of chronic uncomplicated neck pain, a single blind prospective study was designed, to be carried out at a Primary Healthcare Centre, with random assignment to two parallel groups and with evaluation and analysis by independent evaluators. A random assignment was made from 123 patients of the 149 initially recruited. ⋯ By ITT analysis, the change in the pain-VAS variable was greater among the experimental group (28.1 (95% CI 21.4-34.7)). The improvements in quality of life (physical aspect), active neck mobility and reduced rescue medication were clinically and statistically significant. In the treatment of the intensity of chronic neck pain, acupuncture is more effective than the placebo treatment and presents a safety profile making it suitable for routine use in clinical practice.
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Randomized Controlled Trial
Categories of placebo response in the absence of site-specific expectation of analgesia.
Experimental placebo analgesia is induced by building an expectation of reduced pain in a specific body part, usually using an inert cream in the guise of a local anaesthetic in conjunction with conditioning. We investigated non-site-specific placebo analgesia by conditioning subjects to expect the anaesthetic cream on one arm, without specifying if they will definitely receive the cream, or to which arm it might be applied. Painful heat pulses (150 ms) from a CO2 laser were delivered randomly to both arms. ⋯ In the treatment group, we observed a range of placebo responses: unilateral responders (33.3%), subjects with a placebo response in the conditioned arm only; bilateral responders (33.3%), subjects reporting reduction in the intensity ratings in both arms, and non-responders, whose intensity ratings were not influenced by conditioning. We discuss these responses in terms of different levels of expected analgesia, facilitated by the absence of a site-specific focus for the treatment. We suggest this allowed the individuals suggestibility to influence their assessment of the pain experience by combining different levels of expectation with the information from the actual pain stimulus.
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Histamine, substance P, serotonin and bradykinin were applied by iontophoresis to lesional and visually non-lesional skin of 14 patients with atopic dermatitis, and normal skin of 15 healthy volunteers. Itch could be evoked by light stroking of skin with a cotton swab (alloknesis) in all lesional skin sites, but not in non-lesional or normal skin. Substances were applied in the same skin area before and 3 h after administration of placebo or antihistamine (olopatadine hydrochloride: H1-receptor-blocker). ⋯ Histamine- and substance P-induced itch was almost completely suppressed by antihistamines, whereas bradykinin- and serotonin-induced itch was not. This suggests that substance P is a histamine-dependent pruritogen also in lesional skin under sensitized conditions but that bradykinin and serotonin are histamine-independent pruritogens in lesional skin. It is concluded that serotonin and bradykinin, classic endogenous algogens, can turn into potent histamine-independent pruritogens in lesional skin of atopic dermatitis.