Pain
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Randomized Controlled Trial Clinical Trial
The effect of opioid analgesia on exercise test performance in chronic low back pain.
The effect of opioid analgesia on tests of muscular function in chronic low back pain (CLBP) is unknown. Twenty-eight subjects with CLBP of at least moderate intensity performed the Sorensen isokinetic exercise test once after receiving 1 microg/kg fentanyl intravenously and once after placebo in a randomized-order double-blind crossover design. Naloxone 3 microg/kg was administered after the fentanyl phase. ⋯ We presume that the pain relief resulted in increased test performance. Our result is at odds with those of randomized trials which have failed to demonstrate increased function following the treatment of pain with opioid analgesics. This highlights the complexity of the interaction between pain, analgesia and changes in function.
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Randomized Controlled Trial Comparative Study Clinical Trial
Naloxone provokes similar pain facilitation as observed after short-term infusion of remifentanil in humans.
In contrast to an expected preventive analgesic effect, clinical observations suggest that intraoperatively applied opioids can induce postoperative hyperalgesia. We tested the development of post-infusion hyperalgesia in a newly developed experimental model of electrically induced pain and secondary mechanical hyperalgesia. In a double-blind, placebo controlled, cross-over study, 13 subjects received either saline placebo, remifentanil (0.05 or 0.1 microg/kg/min) or naloxone (0.01 mg/kg). ⋯ Naloxone infusion similarly resulted in increased pain (anti-analgesia) (p<0.001) and mechanical hyperalgesia (p<0.01). Increased pain ratings following withdrawal of remifentanil significantly correlated to anti-analgesia evoked by the mu-opioid antagonist naloxone (p<0.01) and was of similar magnitude, suggesting inhibition of endogenous opioids as an underlying mechanism. In contrast, hyperalgesia after remifentanil was more pronounced than hyperalgesia after naloxone administration and did not correlate to the observed anti-analgesic effects, suggesting the involvement of additional receptors systems other than the endorphin system.
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Catastrophizing, or exaggerating the negative consequences of a situation, is associated with higher pain intensity, emotional distress, and functional disability among persons with chronic pain. According to the 'communal coping' model, catastrophizing in persons with pain may function as a social communication directed toward obtaining social proximity, support, or assistance. We tested the hypothesis, based on this model, that social factors would moderate the association between catastrophizing and sensory and affective pain. ⋯ The association between catastrophizing and sensory pain scores was stronger for those who lived with a spouse or partner than for those who lived with someone else. In addition, there was a stronger association between catastrophizing and affective pain for those who reported greater solicitousness in their relationship. The results provide partial support for the communal coping model of catastrophizing.
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Randomized Controlled Trial Clinical Trial
Effects of TENS frequency, intensity and stimulation site parameter manipulation on pressure pain thresholds in healthy human subjects.
This study evaluated the effects of varying frequency, intensity and stimulation site, of transcutaneous electrical nerve stimulation (TENS) in an experimental model of pain. In a double-blind design 240 volunteers were randomised to one of six experimental TENS groups, a sham TENS or control (n=30 per group; gender balanced). Two TENS frequencies (110 or 4 Hz) and two intensities (strong but comfortable or highest tolerable) at a fixed pulse duration (200 micros) were applied at three sites relative to the measurement site (segmentally, extrasegmentally or a combination of these), for 30 min. Pressure pain thresholds (PPT) were measured using a pressure algometer, in the first dorsal interosseous muscle, every 10 min, during stimulation and for a further 30 min. The high frequency, high intensity segmental, and combined stimulation groups, showed rapid onset and significant hypoalgesic effects. This effect was sustained for 20 min post-stimulation in the high frequency segmental group. All other TENS intervention groups showed hypoalgesic responses similar to the sham TENS group, and none of these groups reached a clinically significant hypoalgesic level. ⋯ The role of TENS frequency, intensity and site are pivotal to achieving optimal hypoalgesic effects, during and after stimulation. Clinical applications of these parameter combinations require further investigations.
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Randomized Controlled Trial Clinical Trial
Short-term infusion of the mu-opioid agonist remifentanil in humans causes hyperalgesia during withdrawal.
Numerous animal studies suggest that acute and chronic exposure to opioids can be associated with the development of hyperalgesia, i.e. an increased sensitivity to noxious stimuli. Hyperalgesia has been documented during withdrawal and on occasion while animals were still exposed to opioids. A pivotal role in the genesis of opioid-associated hyperalgesia has been attributed to a pain facilitating system involving the N-methyl-D-aspartate (NMDA)-receptor. ⋯ Co-administration of the NMDA-receptor antagonist S-ketamine abolished observed enlargement of the hyperalgesic skin area. This study provides direct evidence in humans that short-term administration of an opioid can enhance hyperalgesia as observed during withdrawal and points to a potential role of the NMDA-receptor system in mediating such a hyperalgesic response. This study also points to a differential susceptibility of different pain modalities for the expression of hyperalgesia associated with opioid administration.