Pain
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We hypothesized that preoperative emotional distress and pain intensity would predict the occurrence of signs and symptoms of complex regional pain syndrome (CRPS) following total knee arthroplasty (TKA). Depression (Beck Depression Inventory, BDI), anxiety (State Trait Anxiety Inventory, STAI), pain (McGill Pain Questionnaire-Short Form, MPQ), and signs/symptoms meeting IASP criteria for CRPS were assessed preoperatively, and at 1-, 3-, and 6-months postoperatively in 77 patients undergoing TKA. The prevalence of subjects fulfilling CRPS criteria was 21.0% at 1 month, 13.0% at 3 months, and 12.7% at 6 months postoperative. ⋯ Post-TKA patients with CRPS were more depressed at 1-month follow-up (P<0.05) and more anxious at 6-month follow-up (P<0.05) than patients with ongoing non-CRPS pain (all other comparisons non-significant, P>0.10). Overall, results indicate that CRPS-like phenomena occur in a significant number of patients early post-TKA; however, it is not associated with significantly greater complaints of postoperative pain. There appears to be a modest utility for preoperative distress and pain in predicting CRPS signs and symptoms following TKA, although false positive rates are relatively high.
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Comparative Study
Blood pressure but not cortisol mediates stress effects on subsequent pain perception in healthy men and women.
Research has demonstrated that exposure to acute stress may attenuate pain perception. Mechanisms of this effect in humans have not been determined. This study was conducted to determine the extent to which psychophysiological and adrenocortical responses to acute stress predict subsequent pain perception. ⋯ Regression analyses demonstrated that the stress effect on pain ratings was mediated by systolic BP level during stress; however, cortisol responses did not affect this relationship. Mood changes were independent predictors of pain. The study demonstrates that BP changes in response to stress mediate the stress-induced attenuation of pain perception.
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Sex-related differences in the experience of clinical and experimental pain have been widely reported. Females are at elevated risk for developing several chronic pain conditions and women demonstrate greater sensitivity to noxious stimulation in the laboratory. However, relationships between responses to experimental noxious stimuli and the experience of clinical pain have not been well characterized. ⋯ Women with higher pain tolerances showed greater improvement in pain, more reduction in pain-related interference, and more increases in activity level than women with lower pain tolerances. In contrast, pain tolerance was not associated with positive treatment outcomes among men. These results indicate that experimental pain responses may be most clinically relevant for women, and that sex differences may exist in the determinants of pain-treatment outcomes.
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Comparative Study
Peripheral group II metabotropic glutamate receptors mediate endogenous anti-allodynia in inflammation.
We previously demonstrated that activation of peripheral group II mGluRs inhibits PGE2-induced thermal hyperalgesia. In the present study we examined the role of peripheral group II mGluRs in inflammation-induced mechanical allodynia in CD1 mice. Subcutaneous injection of group II mGluR agonists or antagonists into the plantar surface of the mouse hind paw did not alter mechanical thresholds, suggesting that peripheral group II mGluRs did not modulate basal mechanical sensation. ⋯ The application of group II mGluR antagonist (LY341495) alone delayed the recovery of PGE2- and carrageenan-induced mechanical allodynia. Three hours after injection of carrageenan, LY341495-injected mice showed little or no recovery with mechanical thresholds 8+/-1% of pre-carrageenan baselines, compared to 57+/-8% of pre-carrageenan baselines in vehicle-injected mice at the same time point. Our results suggest that activation of peripheral group II mGluRs reduces inflammation-induced mechanical allodynia and that peripheral group II mGluRs may mediate endogenous anti-allodynia effects, which speed recovery from inflammation-induced hypersensitivity.
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The objective of this study was to assess changes in levels of clinical temporomandibular (TMD) pain in relation to phases of the menstrual cycle. TMD cases were 35 women not using oral contraceptives (OCs); 35 women using OCs; and 21 men. Controls were 35 normally cycling women without TMD or other chronic pains. ⋯ There was no statistically significant difference over time periods for men (P=0.94). Similar patterns were found for average pain, as well as PMS symptoms and general somatic symptoms. These results suggest that TMD pain in women is highest at times of lowest estrogen, but rapid estrogen change may also be associated with increased pain.