Anesthesiology
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The authors modeled the influence of remifentanil on the dynamics of sevoflurane using three parameters derived from the electroencephalogram: 95% spectral edge frequency (SEF), canonical univariate parameter (CUP), and Bispectral Index (BIS). ⋯ Remifentanil accelerates sevoflurane blood-brain equilibration without affecting its hypnotic potency as determined from BIS and CUP. In terms of R(2), the authors' pharmacodynamic model describes the anesthetic-BIS relation best.
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Clinical Trial
Morphologic changes in the upper airway of children during awakening from propofol administration.
The purpose of this study was to determine the morphologic changes that occur in the upper airway of children during awakening from propofol sedation. ⋯ The dimensions of the upper airways of children change shape significantly on awakening from propofol sedation. When sedated, the upper airway is oblong shaped, with the A-P diameter larger than the transverse diameter. On awakening, the shape of the upper airway in most children changed such that the transverse diameter was larger. Cross-sectional areas between sedated and awakening states were unchanged. These changes may reflect the differential effects of propofol on upper airway musculature during awakening.
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Excessive extracellular glutamate produced by cerebral ischemia has been proposed to initiate the cascade toward neuronal cell death. Changes in extracellular glutamate concentration are closely linked to changes in intracellular calcium ion concentration. Dantrolene inhibits calcium release from intracellular calcium stores. In this study, the authors investigated the effects of dantrolene on extracellular glutamate accumulation and neuronal degeneration in a rat model of transient global forebrain ischemia. ⋯ Intracerebroventricular dantrolene prevents delayed neuronal loss in the rat hippocampal CA1 region subjected to transient ischemia; however, this neuroprotection cannot be accounted for only by the reduced concentrations of extracellular glutamate during ischemia.
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Volatile anesthetics precondition against myocardial infarction, but it is unknown whether this beneficial action is threshold- or dose-dependent. The authors tested the hypothesis that isoflurane decreases myocardial infarct size in a dose-dependent fashion in vivo. ⋯ Concentrations of isoflurane as low as 0.25 MAC are sufficient to precondition myocardium against infarction. High concentrations of isoflurane may have greater efficacy to protect myocardium during conditions of low coronary collateral blood flow.
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General anesthetics can modulate the 5-hydroxytryptamine type 3 (5-HT3) receptor, which may be involved in processes mediating nausea and vomiting, and peripheral nociception. The effects of the new volatile anesthetic sevoflurane and the gaseous anesthetics nitrous oxide (N2O) and xenon (Xe) on the 5-HT3 receptor have not been well-characterized. ⋯ Inhalational general anesthetics produce diverse effects on the 5-HT3 receptor. Both halothane and isoflurane enhanced 5-HT3 receptor function in a concentration-dependent manner, which is consistent with previous studies. Sevoflurane inhibited the 5-HT3 receptor noncompetitively, whereas N2O and Xe inhibited the 5-HT3 receptor competitively, suggesting the inhibitory mechanism of sevoflurane might be different from those of N2O and Xe.