European journal of pain : EJP
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This study investigates the relationship between depression and continuous pain after lumbar surgery by means of the Beck Depression Inventory (BDI). To assess the possibility that some somatic symptoms are confounded with pain, the items of the inventory were divided into a cognitive-affective and somatic subscale. Data analysis is based on two assumptions: (1) continuous pain after surgery is more closely related to the somatic subscale than to the cognitive-affective subscale of the BDI; and (2) postsurgical pain can be better predicted by the somatic than by the cognitive-affective subscale presurgery. ⋯ Regarding the subscales, the cognitive-affective scale, but not the somatic scale, was related to surgical outcome in this sample. The relationship between presurgical depression and pain at follow-up failed to reach statistical significance in the nucleotomy sample. It is concluded that lack of awareness of the confounding effects of somatic items in questionnaires for the assessment of mood may contribute to erroneous conclusions drawn from studies reported in the literature.
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The study of the mechanisms of thermal and mechanical hyperalgesia produced in human inflammatory conditions is dependent on a reliable, consistent model. The present investigation shows that the intraplantar administration of zymosan in the rat hindpaw produces a reliable and quantifiable thermal and mechanical hyperalgesia accompanied by oedema that closely mimics the symptoms of inflammation in man. Prior to the intraplantar injection of zymosan, there was no significant difference in withdrawal latencies, mechanical withdrawal thresholds or paw thickness between the left and right hindpaws. ⋯ In addition, at the greatest dose tested (6.25 mg), all rats showed evidence of licking, biting and shaking of the injected hindpaw for up to 30-45 min after injection. These data demonstrate that the intraplantar injection of zymosan is a reliable and quantifiable model of tonic pain characterized by a dose- and time-dependent thermal and mechanical hyperalgesia accompanied by a robust oedema. This model is likely to be a useful, reliable model in which to study further the central and peripheral mechanisms of hyperalgesia.
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Patients with complex regional pain syndrome (CRPS) (n=20) were examined in order to evaluate cutaneous reactions to norepinephrine (NE) on both the affected and the unaffected limb in comparison to healthy controls. Sixteen female and four male patients suffering from very acute and therefore untreated CRPS with a mean duration of 5.5 weeks were included in this study. Two groups of healthy volunteers served as control groups: the first group (n=18) according to the same study protocol as CRPS patients, and the second group (n=10) after warming up one limb. ⋯ The second control group had an increased unilateral skin temperature after warming up (35.0 vs 34.3 degrees C, p<0.006) and demonstrated a significantly increased vasoconstriction on the warmer side (52.0 vs 20.2%, p<0.03) corresponding to findings in patients with acute CRPS. The present study proves that there are signs of decreased sympathetic activity in the affected limb in very acute CRPS. However, no indication was found for increased sensitivity of vascular alpha-receptors in the very acute stages of CRPS, and there was also no indication for a significant direct contribution of the sympathetic nervous system to pain in very acute CRPS.