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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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
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.
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Randomized Controlled Trial Clinical Trial
Lack of analgesic efficacy of oral delta-9-tetrahydrocannabinol in postoperative pain.
We have evaluated the efficacy of delta-9-tetrahydrocannabinol (delta-9-THC), the main psychoactive constituent of cannabis, in postoperative pain. In a randomized double-blind, placebo-controlled, single-dose trial, we investigated 40 women undergoing elective abdominal hysterectomy. Randomization took place when postoperative patient-controlled analgesia was discontinued on the second postoperative day. ⋯ Increased awareness of surroundings was reported more frequently in patients receiving delta-9-THC (40 vs 5%, P=0.04). There were no other significant differences with respect to adverse events. This study demonstrates no evidence of an analgesic effect of orally administered delta-9-THC 5 mg in postoperative pain in humans.
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Emotions have been shown to alter pain perception, but the underlying mechanism is unclear since emotions also affect attention, which itself changes nociceptive transmission. We manipulated independently direction of attention and emotional state, using tasks involving heat pain and pleasant and unpleasant odors. Shifts in attention between the thermal and olfactory modalities did not alter mood or anxiety. ⋯ In contrast, odor valence altered mood, anxiety level, and pain unpleasantness, but did not change the perception of pain intensity. Pain unpleasantness ratings correlated with mood, but not with odor valence, suggesting that emotional changes underlie the selective modulation of pain affect. These results show that emotion and attention differentially alter pain perception and thus invoke at least partially separable neural modulatory circuits.