European journal of pain : EJP
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Systemic morphine selectively depresses a thalamic link of widespread nociceptive inputs in the rat.
The lateral part of the ventromedial thalamus (VM l) relays nociceptive inputs from the whole body surface to the dorsolateral frontal cortex. The aim of the present study was to investigate the effects of systemic morphine on nociceptive activity evoked in VM l neurones either by thermal (48 degrees C) or by supramaximal percutaneous electrical stimuli. The noxious thermal evoked responses were depressed by 10.8 +/- 10.1%, 48.3 +/- 23.0% and 67.3 +/- 10.1%, 5 min after i.v. injections of 1.0, 1.73 and 3.0 mg/kg of morphine, respectively. ⋯ The dose of morphine that reduced VM l neuronal nociceptive responses by 50% (1.73 mg/kg) was around 3.5 times lower than that necessary to inhibit the responses of its spinal or medullary relays under similar experimental conditions. These results, added to the data of the literature, suggest that supraspinal effects of morphine are primarily mediated at the thalamic level. It is tempting to speculate that morphine-induced reductions of attentional or psychomotor responses related to pain may be mediated by its action on VM l.
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The overall aim of this study was to explore the natural course of pain-related fear during the early stage of a new low back pain episode, using a prospective case series design. Specific research questions addressed the existence of typical patterns in individual time series of pain-related fear and sequential relationships between the occurrence of pain-related fear, pain and pain catastrophizing. Forty-four general practice patients who consulted their physician with a new episode of non-specific low back pain were recruited. ⋯ In summary, these results fit in with previous findings in chronic patients. A relevant subgroup of patients who might benefit from early intervention could be identified. These findings support the need for further research into fear mechanisms in acute low back pain.
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Although the modified Stroop paradigm is considered to be a prominent paradigm for investigating selective attention in emotional disorders, relatively few studies have applied this paradigm to examine selective attention in chronic pain patients. Moreover, the results from these studies are not robust. The purpose of this article is to review the evidence for attentional bias in chronic pain patients, by means of a meta-analysis. ⋯ Thus, the results from the present meta-analysis on studies applying the modified Stroop paradigm suggest that chronic pain patients selectively attend to both pain sensory and pain affective stimuli. Furthermore, the MD estimation did not depend on the methodological quality, tentatively indicating that even though studies differed in methodology, the results were rather consistent. Implications of the results are discussed.
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The continuous intrathecal infusion of drugs with implantable and programmable pumps is commonly used for the treatment of otherwise intractable pain and spasticity. There is now a consensus that it is possible to use mixtures of two or even three drugs in selected cases. ⋯ These values are determined from the desired quantity of each drug to be infused in 24h, the concentration of each drug solution and the volume of the reservoir. It is essential that the drugs do not react with one another, that they will remain stable in the reservoir at body temperature and that they are safe for a long-term infusion.
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Clinical Trial
Morphine responsiveness in a group of well-defined multiple sclerosis patients: a study with i.v. morphine.
Pain in multiple sclerosis (MS) is more common than has previously been believed. About 28% of all MS patients suffer from central pain (CP), a pain that is difficult to treat. In the present study we have investigated the responsiveness of this pain to morphine. ⋯ Thus, compared with nociceptive pain, only a minority of the patients with CP due to MS responded to morphine and only at high doses. The present results are in accord with experimental studies indicating that neuropathic pain is poorly responsive but not totally unresponsive to opioids. The results do not support the routine use of strong opioids in MS patients with CP.