Pain
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Randomized Controlled Trial Clinical Trial
Experimental incision-induced pain in human skin: effects of systemic lidocaine on flare formation and hyperalgesia.
In order to try to gain a better understanding of the mechanisms of post-operative pain, this study was designed to psychophysically determine physiological and pharmacological characteristics of experimental pain induced by a 4-mm-long incision through the skin, fascia and muscle in the volar forearm of humans. In experiment 1, the subjects (n=8) were administered lidocaine systemically (a bolus injection of 2mg/kg for a period of 5 min followed by an intravenous infusion of 2mg/kg/h for another 40 min), and then the incision was made. In experiment 2, cumulative doses of lidocaine (0.5-2mg/kg) were systemically injected in the subjects (n=8) 30 min after the incision had been made, when primary and secondary hyperalgesia had fully developed. ⋯ Pre-traumatic treatment with lidocaine would temporarily stabilize the sensitized nerves in the injured area, but the nerves would be sensitized after completion of the administration. Post-traumatic treatment with lidocaine reduced primary and secondary hyperalgesia that had fully developed. However, the finding that the suppressive effect of lidocaine on secondary hyperalgesia was temporary suggests that the development and maintenance of secondary hyperalgesia are caused by different mechanisms.
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Clinical Trial Controlled Clinical Trial
The relationship between resting blood pressure and acute pain sensitivity in healthy normotensives and chronic back pain sufferers: the effects of opioid blockade.
Resting blood pressure is inversely correlated with acute pain sensitivity in healthy normotensives. This study tested: (1) whether endogenous opioid activity is necessary for this adaptive relationship to occur, (2) whether this relationship is altered in chronic low back pain (LBP), and (3) whether endogenous opioid dysfunction underlies any such alterations. Fifty-one pain-free normotensives and 44 normotensive chronic LBP sufferers received opioid blockade (8 mg naloxone i.v.) or placebo blockade (saline) in randomized, counterbalanced order in separate sessions. ⋯ Opioid blockade exerted no significant main or interaction effects in these combined groups analyses (p values >0.10). Higher DBP was associated with greater clinical pain intensity among the LBP subjects (P<0.001). Overall, these results suggest: (1) endogenous opioids do not mediate the inverse relationship between resting blood pressure and acute pain sensitivity in pain-free normotensives; (2) the BP-pain sensitivity relationship is altered in chronic pain, suggesting dysfunction in pain regulatory systems, and (3) these alterations are not related to opioid dysfunction.
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This study assessed spatial and temporal aspects of pressure pain during increasing and constant compressions using a cuff algometer and during adaptive compressions using a closed-loop feedback system for maintaining stable pain. Experimental setup consisted of a pneumatic tourniquet cuff, a computer-controlled air compressor, and a 10-cm electronic visual analogue scale (VAS). The first experiment assessed spatial summation for cuff pain by recording the pressure-pain stimulus-response (SR) function during increasing compressions with single and double cuffs. ⋯ The oscillating pressure generated by closed-loop system led to constant rather than adapting pain at intensities of 2, 4, and 6 cm on the VAS. The cuff algometer is highly configurable tool for assessment of pain sensitivity by pressure-pain and time-pain functions. The presented models are useful additions to a researcher's armamentarium for further pharmacological and clinical studies on deep tissue pain and related mechanisms.
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The purpose of this study was to describe race/ethnic differences in the use of formal health care services for painful oral symptoms by older adults. We also considered the sex of the respondent rather than assuming that males and females within a specific racial group would use health care services similarly. To our knowledge, these specific utilization patterns have never been reported before in the pain literature. ⋯ Pain at its worst was a positive predictor for four of the five analyses (jaw joint pain, painful oral sores, temperature sensitivity, and toothache pain). The duration variable (years with pain) was a negative predictor of health care use. This is consistent with the conclusion that individuals seek care early in the course of the symptom, i.e. an active care seeking phase, make emotional or physical adjustments, and then resign themselves to the symptoms.
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The present study examined the value of a measure of catastrophizing as a predictor of activity intolerance in response to delayed onset muscle soreness (DOMS). A sample of 50 (17 men, 33 women) sedentary undergraduates participated in an exercise protocol designed to induce muscle soreness and were asked to return 2 days later to perform the same physical maneuvers. Participants performed five strength exercises that emphasized the eccentric component of the muscle contraction in order to induce DOMS. ⋯ Regression analyses revealed that catastrophizing predicted reductions in weight lifted even after controlling for pain and negative mood. These findings extend previous research in demonstrating that catastrophizing is associated with objective indices of activity intolerance associated with pain. Implications of these findings for understanding pain-related disability are addressed.