Pain
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Chemical cauterization of the central cornea with silver nitrate was assessed as a superficial injury model of tissue sensitization accompanying acute inflammation. Adult male Sprague-Dawley rats were anesthetized with halothane gas, and the centers of their right corneas treated with a silver nitrate applicator stick (75% silver nitrate, 25% potassium nitrate) to produce a discrete lesion 1 mm in diameter. Edema of the corneal stroma and elevated immune cell counts became significant 4 h after cauterization, and were still evident after 48 h. ⋯ A significant increase in stimulus-induced blinking was evident 2 h after cauterization. Chemical sensitization peaked at 6 h, and was no longer significant at 12 h. We conclude that silver nitrate cauterization produces acute corneal inflammation and hyperalgesia, and may prove a useful model for the study of primary afferent nociceptors.
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Comparative Study
The parents' postoperative pain measure: replication and extension to 2-6-year-old children.
Pain assessment is a difficult task for parents at home following children's surgery. The purpose of the present study was to confirm the psychometric properties of a behavioural measure of postoperative pain developed to assist parents with pain assessment in children aged 7-12 years following day surgery. The study also examined the reliability and validity of the measure with children aged 2-6 years. ⋯ As global pain ratings decreased from Days 1 to 2, so did scores on the PPPM. Scores on the PPPM were successful in discriminating between children who had undergone low/moderate and high pain surgeries. The results of this study provide evidence of the reliability and validity of the PPPM as a measure of postoperative pain among children aged 2 through to 12 years.
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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.