Pain
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Case Reports Clinical Trial
Effect of intravenous sodium amytal on cutaneous limb temperatures and sympathetic skin responses in normal subjects and pain patients with and without Complex Regional Pain Syndromes (type I and II). I.
This study examined the effects of intravenous administration of sodium amytal (SA), a medium action barbiturate, on cutaneous limb temperatures and sympathetic skin responses (SSR) to electrical stimulation. Eight normal volunteers and 13 patients with musculoskeletal pain, somatoform pain disorders or nerve/root injury (with findings strictly limited to the distribution of the distribution of the involved nerve) were compared to 15 patients with Complex Regional Pain syndromes (one of whom had documented nerve injury). ⋯ SSR were reduced or lost in a few limbs only in all three groups, irrespective of the increase or decrease of limb temperature and the side of symptoms. We argue that the enhanced thermogenic effect of SA in CRPS patients is due to generalized central changes of thermoregulatory control specifically in this group.
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This study evaluated the effects of spinal gamma-aminobutyric acid (GABA) receptor agonists on the tactile allodynia observed in rats with ligation of the L5/L6 nerve roots (Chung model) and chronic lumbar intrathecal catheters. In these rats, the spinal injection of the GABAB agonist baclofen (BAC; 0.03-03 micrograms) and GABAA agonist muscimol (MUS; 0.1-1.0 micrograms) resulted in a dose-dependent antagonism of the allodynia at doses which had no detectable effect upon motor function. ⋯ The antagonistic effects were limited to the agonist of the respective receptor. These observations indicate that spinal GABAA and GABAB receptors modulate spinal systems activated by low threshold mechanoreceptors which mediate the allodynia observed following peripheral nerve injury.
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Chronic pain in elderly people has only recently begun to receive serious empirical consideration. There is compelling evidence that a significant majority of the elderly experience pain which may interfere with normal functioning. ⋯ Three significant factors which may contribute to this are (1) lack of proper pain assessment; (2) potential risks of pharmacotherapy in the elderly; and (3) misconceptions regarding both the efficacy of nonpharmacological pain management strategies and the attitudes of the elderly towards such treatments. In this review the most commonly used assessment instruments and patterns of age differences in the experience of chronic pain are described and evidence for the efficacy of psychological pain management strategies for this group is reviewed.
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Case Reports Clinical Trial Controlled Clinical Trial
Effect of intravenous sodium amytal on cutaneous sensory abnormalities, spontaneous pain and algometric pain pressure thresholds in neuropathic pain patients: a placebo-controlled study. II.
This study investigated the behaviour exhibited by 17 neuropathic pain patients (almost half of whom had documented neurological injury) with diffuse pain and extraterritorial sensory, sudomotor and vasomotor abnormalities, under the influence of intravenous administration of saline-controlled sodium amytal (SA), a medium action barbiturate. After SA (but not after normal saline) infusion, there was a dramatic and selective reduction of allodynia (touch-evoked pain) in all patients displaying this phenomenon, while pin prick and cold hypo- or hyperalgesia, as well as algometric pressure thresholds of the symptomatic limb (as a measurement of deep pain) were minimally changed in most patients. Spontaneous subjective pain was reduced substantially but not totally. ⋯ Sympathetic blocks and A-fibre ischemic blocks in several patients and spinal stimulation in one patient produced effects identical to those observed during SA administration. The deep pain component was maintained despite elimination of allodynia even under stages of sleep induced by SA, at which time the patients would withdraw only the symptomatic limb upon firm but gentle palpation. We argue that neuropathic pain patients have two separate pain components, a cutaneous one (touch-evoked pain or allodynia) mediated by large fibres as a product of central sensitization, and a deep pain component mediated via nociceptors, which can be easily discriminated during systemic administration of SA.
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Case Reports
Intravenous methadone for cancer pain unrelieved by morphine and hydromorphone: clinical observations.
Methadone is a very effective second-line opioid for treatment of cancer pain. However, the starting doses of methadone indicated on opioid conversion charts may over-estimate the dose of intravenous (i.v.) methadone needed. ⋯ All four patients had excellent pain relief without significant side effects at a dose that, according to the available conversion charts, was approximately 3% of the calculated equianalgesic dose of hydromorphone. When converting from continuous i.v. hydromorphone to continuous i.v. methadone, much lower doses than those suggested by the opioid conversion charts should be used as starting doses.