Pain
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Review Meta Analysis
Evidence for working memory deficits in chronic pain: a systematic review and meta-analysis.
People with chronic pain commonly report impaired cognitive function. However, to date, there has been no systematic evaluation of the body of literature concerning cognitive impairment and pain. Nor have modern meta-analytical methods been used to verify and clarify the extent to which cognition may be impaired. ⋯ High heterogeneity within the field was found with the inclusion of 24 papers using 21 different working memory tests encompassing 9 different working memory constructs and 9 different chronic pain populations. Notwithstanding high heterogeneity, pooled results from behavioural outcomes reflected a consistent, significant moderate effect in favour of better performance by healthy controls and, with the exception of one study, pooled results from physiological outcomes reflected no evidence for an effect. Future research would benefit from the use of clearly defined constructs of working memory, as well as standardised methods of testing.
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Research shows that placebo analgesia can be induced through social observational learning. Our aim was to replicate and extend this result by studying the effect of the sex of both the model and the subject on the magnitude of placebo analgesia induced by social observational learning. Four experimental (1 through 4) and 2 control (5 and 6) groups were observed: groups 1, 3, and 5 were female; groups 2, 4, and 6 were male. ⋯ Regardless of the sex of the subject, nocebo hyperalgesia was greater after the male model was observed. The results show that social observational learning is a mechanism that produces placebo effects. They also indicate that the sex of the model plays an important role in this process.
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Dental pain, including toothache, is one of the most prevalent types of orofacial pain, causing severe, persistent pain that has a significant negative effect on quality of life, including eating disturbances, mood changes, and sleep disruption. As the primary cause of toothache pain is injury to the uniquely innervated dental pulp, rodent models of this injury provide the opportunity to study neurobiological mechanisms of tissue injury-induced persistent pain. Here we evaluated behavioral changes in mice with a dental pulp injury (DPI) produced by mechanically exposing the pulp to the oral environment. ⋯ Surprisingly, mice with DPI increased their consumption of sucrose solution, to over 150% of baseline, regardless of temperature. Both the weight loss and increased sucrose intake in the first 2 days of injury were reversed by administration of indomethacin. These findings indicate that enhanced sucrose consumption may be a reliable measure of orofacial pain in rodents, and suggest that alterations in energy expenditure and motivational behaviors are under-recognized outcomes of tooth injury.
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We tested whether the combination of a reduced dose of a local anesthetic (LA) with an opioid compared with a standard dose of the same LA alone guaranteed adequate intraoperative anesthesia and postoperative analgesia and decreased LA-related adverse effects. We systematically searched (to November 2012) for randomized comparisons of combinations of a reduced dose of an LA with a concomitant opioid (experimental) with a standard dose of the LA alone (control) in adults undergoing surgery with single-injection intrathecal anesthesia without general anesthesia. We included 28 trials (1393 patients). ⋯ There was also evidence of a decrease in the risk of shivering (risk ratio [RR]: 0.26; 95% confidence interval [CI]: 0.12-0.56), nausea (RR: 0.45; 95% CI: 0.31-0.66), and arterial hypotension (RR: 0.52; 95% CI: 0.35-0.78). The risk of pruritus was increased (RR: 11.7; 95% CI: 6.2-21.9). Adding an opioid to a reduced dose of an intrathecal LA can decrease LA-related adverse effects and improve recovery from the spinal block without compromising intraoperative anesthesia or duration of postoperative analgesia.
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Recent functional brain connectivity studies have contributed to our understanding of the neurocircuitry supporting pain perception. However, evoked-pain connectivity studies have employed cutaneous and/or brief stimuli, which induce sensations that differ appreciably from the clinical pain experience. Sustained myofascial pain evoked by pressure cuff affords an excellent opportunity to evaluate functional connectivity change to more clinically relevant sustained deep-tissue pain. ⋯ Moreover, greater connectivity during pain between contralateral S1/M1 and posterior insula, thalamus, putamen, and amygdala was associated with lower cuff pressures needed to reach the targeted pain sensation. These results demonstrate that sustained pain disrupts resting S1/M1 connectivity by shifting it to a network known to process stimulus salience. Furthermore, increased connectivity between S1/M1 and both sensory and affective processing areas may be an important contribution to interindividual differences in pain sensitivity.