Anesthesiology
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Previous imaging studies have demonstrated a number of cortical and subcortical brain structures to be activated during noxious stimulation and infusion of narcotic analgesics. This study used O-water and positron emission tomography to investigate dose-dependent effects of the short-acting mu-selective opioid agonist remifentanil on regional cerebral blood flow during experimentally induced painful heat stimulation in healthy male volunteers. ⋯ Remifentanil induced regional cerebral blood flow increases in the cingulofrontal cortex and periaqueductal gray during pain stimulation, indicating that mu-opioidergic activation modulates activity in pain inhibitory circuitries. This provides direct evidence that opioidergic analgesia is mediated by activation of established descending antinociceptive pathways.
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The authors previously validated in an animal model a new indicator dilution technique for measuring cardiac output and circulating blood volume by recording transcutaneously the fluorescence of circulating indocyanine green with an optical probe placed on the skin surface. The current study compared fluorescence dilution recordings recorded from several locations on the human face in terms of signal intensity and stability and estimated the subjects' cardiac output and circulating blood volume from the recordings. ⋯ The study demonstrates that intense and reproducible fluorescence dilution signals can be measured transcutaneously in healthy humans and could potentially be used to measure cardiac output and circulating blood volume minimally invasively.
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A single dose of the macrolide antibiotic erythromycin can induce tolerance against cerebral ischemia in vivo (pharmacologic preconditioning). This study identified potential mechanisms of tolerance induction by assessing effects of erythromycin preconditioning on the cerebral transcriptional response to transient global cerebral ischemia. ⋯ These findings present a new molecular correlate for the induction of ischemic tolerance achieved by erythromycin preconditioning and will further the understanding of this clinically important new regimen of preemptive neuroprotection.
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Postoperative cognitive dysfunction is being increasingly reported as a complication. The authors investigated the role of cytokine-mediated inflammation within the central nervous system in the development of cognitive dysfunction in a rat model. ⋯ These results suggest that splenectomy performed during neuroleptic anesthesia triggers a cognitive decline that is associated with a hippocampal inflammatory response that seems to be due to proinflammatory cytokine-dependent activation of glial cells.