Pain
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Randomized Controlled Trial
Acidic buffer induced muscle pain evokes referred pain and mechanical hyperalgesia in humans.
While tissue acidosis causes local deep-tissue pain, its effect on referred pain and mechanical muscle hyperalgesia is unknown. The aim of this study was to investigate a human experimental acidic muscle pain model using a randomized, controlled, single-blinded study design. Seventy-two subjects (36 female) participated in three visits, each involving one 15 min intramuscular infusion into the anterior tibialis muscle: acidic phosphate buffer (pH 5.2) at 40 ml/h (N=69) or 20 ml/h (N=54), normal phosphate buffer (pH 7.3) at 40 ml/h (N=70), or isotonic saline at 40 ml/h (N=19). ⋯ PPTs decreased at the ankle in those with referred pain in response to acidic buffer, i.e. referred mechanical hyperalgesia, but not at the foot. No pain or changes in PPTs occurred in the contralateral leg. These results demonstrate muscle acidosis can lead to local and referred pain and hyperalgesia, with significant sex differences in development of referred pain.
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Randomized Controlled Trial
Efficacy of percutaneous electrical nerve stimulation and therapeutic exercise for older adults with chronic low back pain: a randomized controlled trial.
Chronic low back pain (CLBP) in older adults may be disabling and therapeutically challenging, largely because of the inefficacy and/or morbidity associated with traditional pain treatment. We conducted a randomized controlled trial in 200 men and women > or = age 65 with CLBP to evaluate the efficacy of percutaneous electrical nerve stimulation (PENS) with and without general conditioning and aerobic exercise (GCAE), for reducing pain and improving physical function. Participants were randomized to receive (1) PENS, (2) control-PENS (brief electrical stimulation to control for treatment expectancy), (3) PENS+GCAE, or (4) control-PENS+GCAE, twice a week for 6 weeks. ⋯ There were no significant side effects. Since brief electrical stimulation (i.e., control-PENS) facilitated comparably reduced pain and improved function at 6 months as compared with PENS, the exact dose of electrical stimulation required for analgesia cannot be determined. GCAE was more effective than PENS alone in reducing fear avoidance beliefs, but not in reducing pain or in improving physical function.
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The analgesic effects of morphine are mediated, in part, by periaqueductal gray (PAG) neurons that project to the rostral ventromedial medulla (RVM). Although much of the neural circuitry within the RVM has been described, the relationship between RVM neurons and PAG input and spinal output is not known. The objective of this study was to determine whether GABAergic output neurons from the PAG target RVM reticulospinal neurons. ⋯ Similar to the pattern reported above, both GAD67- and non-GAD67-immunoreactive PAG neurons project to RVM ON, OFF, and Neutral cells in the RVM. These inputs include a GAD67-immunoreactive projection to a GAD67-immunoreactive ON cell and non-GAD67 projections to GAD67-immunoreactive OFF cells. This pattern is consistent with PAG neurons producing antinociception by direct excitation of RVM OFF cells and inhibition of ON cells.
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There is an abundance of studies concerning depression and pain, while the mechanisms and the relationships of anger expression and pain are less well known. The validity of commonly used depression questionnaires as measures of depression in pain patients has been questioned, as they include items which can be related to the pain problem as well as to signs of depression. The aim of this study was to investigate the relationships between pain severity, various signs of depression, and anger management style. ⋯ In patients with more severe pain, the relationships between anger management style, specifically, inhibition of anger and depression were strong, while no such relationships were found in the group of patients with less severe pain. No correlations were found between pain intensity and depression as measured by the sum score of the BDI. However, analysing separately the two subscales of the BDI, negative view and physical function, significant positive relationships between pain intensity and both subscales appeared.
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Over the past decade, the importance of acceptance of chronic pain has been demonstrated. Acceptance has often been assessed using the 20-item, two-factor Chronic Pain Acceptance Questionnaire (CPAQ; McCracken, Vowles, Eccleston, Pain 2004;107:159-66). This two-factor model has been supported but awaits further confirmation. ⋯ Follow-up analyses indicated significant differences among the clusters across multiple measures of functioning. The cluster with low CPAQ scores reported more difficulties in comparison to the group with high scores, while the group with discrepant CPAQ scores generally reported difficulties that fell in between. These results provide further support for the 20-item, two-factor CPAQ and indicate that it is both theoretically and practically useful.