Anesthesiology
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Results from previous studies on the effect of nitrous oxide (N2O) on the cerebral circulation are conflicting. Early reports claim N2O to have no effect whereas recent findings demonstrate a cerebral cortical vasodilatation during N2O inhalation, but the regional cerebral blood flow (CBF) in the subcortical structures is unknown. ⋯ Inhalation of 50% N2O increased global CBF mainly by augmenting flow in frontal brain structures. In contrast, changes in carbon dioxide without N2O affected CBF uniformly in the brain. The uneven change in distribution of the CBF when N2O was added during hypocapnia, the reduced carbon dioxide response, and the lack of effect of N2O on isolated human pial arteries suggest that N2O may increase metabolism in selected brain areas.
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The alpha 2-adrenergic agonist, dexmedetomidine, alters hemodynamics by diminishing sympathetic and/or augmenting parasympathetic neurogenic tone to the heart and peripheral vasculature. However, the specific actions of dexmedetomidine on baroreceptor function are unknown. The purpose of the current investigation was to determine baroreceptor function during an anesthetic state produced by halothane and a similar anesthetic state produced by halothane after dexmedetomidine pretreatment. ⋯ The results indicate that dexmedetomidine alone does not alter baroreflex sensitivity. In addition, possibly through an anesthetic-sparing action, dexmedetomidine preserves baroreflex responses during halothane anesthesia. Such a preservation of the baroreceptor reflex by dexmedetomidine might provide an important mechanism for maintenance of cardiovascular stability by retaining buffer reflexes during general anesthesia.
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A decrease in myocardial perfusion pressure may reduce myocardial blood flow. However, it may not significantly affect myocardial perfusion when in presence of a concurrent coronary artery vasodilation. However, the effects of propofol in coronary arteries are not well determined. In this study, the effects of propofol on porcine coronary artery responses to vasoactive agents that operate through voltage- and receptor-mediated calcium mechanisms were investigated. ⋯ Propofol possesses vasodilator effect and attenuates the effects of vasoconstrictor agents in porcine coronary artery. Further, an antagonism of calcium channels may be responsible for these effects of propofol.