Pain
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Randomized Controlled Trial Clinical Trial
Intraarticular morphine versus dexamethasone in chronic arthritis.
Intraarticular morphine inhibits pain after knee surgery without overt toxicity. This study examined intraarticular morphine in chronic arthritis. We undertook a randomized double-blind comparison between intraarticular morphine (3 mg), dexamethasone (4 mg) and saline (3 ml) in 44 patients with chronic inflammatory arthritis or osteoarthritis of the knee. ⋯ No patient displayed untoward side effects. Synovial leukocyte counts were lower after morphine than after saline. In conclusion, intraarticular morphine produces analgesia of similar magnitude to dexamethasone and it may have antiinflammatory actions in chronic arthritis.
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The objective of this study was to investigate the central processing of dynamic mechanical allodynia in patients with mononeuropathy. Regional cerebral blood flow, as an indicator of neuronal activity, was measured with positron emission tomography. Paired comparisons were made between three different states; rest, allodynia during brushing the painful skin area, and brushing of the homologous contralateral area. ⋯ This finding is consistent with previous studies suggesting attentional modulation and a central coping strategy for known and expected painful stimuli. Involvement of the medial pain system has previously been reported in patients with mononeuropathy during ongoing spontaneous pain. This study reveals a bilateral activation of the lateral pain system as well as involvement of the medial pain system during dynamic mechanical allodynia in patients with mononeuropathy.
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Expression of bradykinin receptors was analyzed in freshly isolated dorsal root ganglion neurons of the ipsi- and contralateral segments L4/L5, L2/L3, and T12/T13 two to twenty days after unilateral injury of the adult rat sciatic nerve using gold labeled bradykinin. The number of infiltrating leucocytes was investigated by flow cytometry. Sciatic nerve injury transiently increased the proportion of neurons expressing bradykinin receptors not only in the ipsilateral ganglia L4/L5, but also in the homonymous contralateral ganglia and also bilaterally in the adjacent ganglia L2/L3. ⋯ No increase was observed prior to day ten and only in ipsilateral ganglia L4/L5, not contralaterally and not in adjacent ganglia L2/L3 and T12/T13. The experiments show that the induction of bradykinin receptors following a unilateral nerve lesion is not restricted to neurons projecting into the damaged nerve but is (i) bilateral, (ii) different in time course between injured and uninjured neurons, and (iii) locally confined to neurons of the adjacent ganglia. Macrophages and lymphocytes are increased after ten day ligation only in the affected ganglia and are probably not involved in the induction of bradykinin receptors.
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A number of studies have examined the effects of naloxone on nitrous oxide-induced analgesia with conflicting results. In the present study the effects of a relatively high dose of naloxone was examined to determine its effects on nitrous oxide-induced analgesia, as well as on the subjective and psychomotor effects of nitrous oxide. Fourteen subjects participated in a four-session crossover trial in which they received intravenous injections of either saline or 30mg/70kg naloxone 10min into a 35min period in which they were inhaling either 100% oxygen or 30% nitrous oxide in oxygen. ⋯ Subjects reported higher pain ratings after the naloxone injection than the saline injection, but there was no evidence of naloxone reversing the analgesic effects of nitrous oxide. Similarly while naloxone also affected mood and impaired psychomotor performance, there was no evidence of naloxone reversing the effect of nitrous oxide on these measures. The results of this study call into question the role of the opioidergic system in mediating various effects of nitrous oxide in humans.
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Considerable research indicates increased experience of clinical pain among females relative to males, and females also demonstrate enhanced responses to experimentally-induced pain. However, previous research has not investigated the relationship between clinical and experimental pain responses in healthy females and males. This experiment examined recent clinical pain as well as thermal pain thresholds and tolerances in 209 (117 female, 92 male) healthy young adults. ⋯ The differences remained significant after correcting for psychological variables including hypervigilance and sex role expectancies. These results indicate that experimental pain responses may be more clinically relevant for females than males. Potential explanations and implications for this pattern of results are discussed.