Pain
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We developed and validated a prediction rule for the occurrence of early postoperative severe pain in surgical inpatients, using predictors that can be easily documented in a preoperative setting. A cohort of surgical inpatients (n=1416) undergoing various procedures except cardiac surgery and intracranial neurosurgery in a University Hospital were studied. Preoperatively the following predictors were collected: age, gender, type of scheduled surgery, expected incision size, blood pressure, heart rate, Quetelet index, the presence and severity of preoperative pain, health-related quality of life the (SF-36), Spielberger's State-Trait Anxiety Inventory (STAI) and the Amsterdam Preoperative Anxiety and Information Scale (APAIS). ⋯ The reliability of this extended model was good (Hosmer and Lemeshow test p-value 0.78). We have demonstrated that severe postoperative pain early after awakening from general anesthesia can be predicted with a scoring rule, using a small set of variables that can be easily obtained from all patients at the preoperative visit. Before this internally validated preoperative prediction rule can be applied in clinical practice to support anticipatory pain management, external validation in other clinical settings is necessary.
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Comparative Study
Effects of local pressure and vibration on muscle pain from eccentric exercise and hypertonic saline.
In human subjects the triceps surae of one leg was exercised eccentrically by asking subjects to walk backwards on an inclined treadmill. Before the exercise controlled local pressure, applied to the muscle with an electromagnet, produced mild soreness, which was reduced when the pressure was combined with vibration. When delayed-onset muscle soreness (DOMS) had set in, 24-48 h after the exercise, vibration increased pain from local pressure. ⋯ In a subject with DOMS, local pressure again increased pain from saline by 32% but combining it with vibration increased pain further by an additional 20%. The effect of vibration on DOMS could be abolished with a large nerve fibre block applied to the sciatic nerve. It is concluded that the vibration effects are the result of stimulation of large-diameter mechanoreceptive afferents in the muscle which, it is speculated, play a role in generating DOMS.
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Numerous clinical studies have reported successful relief of chronic pain with sensory thalamic stimulation. However, even with the extensive use of sensory thalamic stimulation as a clinical tool in the relief of chronic pain, the results are still inconsistent. This discrepancy could probably be explained by the fact that the majority of these studies are case reports or retrospective analyses, which have often used imprecise pain measurements that do not allow a rigorous statistical evaluation of pain relief. ⋯ On the other hand, neither thalamic nor placebo stimulation affected air puff and visual ratings, suggesting that the effect applies specifically to pain and hence is not caused by a general change in attention. The level of paresthesia elicited during the placebo manipulation was also directly correlated with the degree of placebo pain relief. These results suggest that thalamic stimulation produces a small but significant reduction in pain perception, but that a significant placebo effect also exists.
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The contribution of four cortical areas (S1, S2, insular cortex and gyrus cinguli) to pain processing was assessed by functional magnetic resonance imaging (fMRI). Phasic (mechanical impact) and tonic stimuli (squeezing) were applied to the back of a finger, both at two different strengths. Stimuli were adjusted to inflict weak and strong pain sensations. ⋯ Though the insular cortex was often bilaterally activated, no significant differences between stimulus quality or intensity were found. Our results provide evidence for a contribution of the S2 projection area and of the cingulate cortex to the processing of the intensity dimension of phasic mechanical pain. Such evidence was not found for the S1 area, which probably receives dominant input from non-nociceptive mechanoreceptors.