Anesthesiology
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Comparative Study Clinical Trial
Fenoldopam improves renal hemodynamics impaired by positive end-expiratory pressure.
Mechanical ventilation with positive end-expiratory pressure (PEEP) can impair renal hemodynamics. Fenoldopam, a dopamine receptor agonist, has been shown, in animal experiments, to improve renal perfusion. The purpose of the current study was to examine the effects of this agent on altered renal hemodynamics secondary to positive pressure ventilation. ⋯ The results of the current study indicate that intravenous fenoldopam at a dose of 0.2 micrograms.kg-1.min-1 improves renal hemodynamics and increases Na and K excretion in patients requiring mechanical ventilation of their lungs and PEEP. These effects are probably caused by an increased kidney perfusion secondary to renal artery vasodilation.
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Severe exercise and administration of vasopressors may adversely affect pulmonary gas exchange in humans. The role of increases in pulmonary perfusion in worsening ventilation-perfusion (VA/Q) relationships is unclear, however, because concomitant changes in ventilation and alveolar gas composition occur. The purpose of this study was to determine whether increasing of lobar blood flow increased VA/Q heterogeneity in the absence of changes in respiratory parameters. ⋯ Marked increases in lobar blood flow and Ppa worsened pulmonary gas exchange. The degree of impairment was correlated with the degree of increase in lobar perfusion. However, increased lobar perfusion did not affect LLL pulmonary venous blood oxygenation because the decrease in PO2, due to increased VA/Q mismatch, was opposed by an increase in PO2, due to increased PvO2.
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The molecular mechanism of propofol anesthesia has been related to facilitation of the inhibitory neurotransmission mediated by gamma-aminobutyric acid (GABA). In the current study, the authors examined the direct actions of propofol on the acutely dissociated mammalian central neurons. ⋯ Propofol at clinically relevant concentrations directly activates the GABAA receptor-chloride ionophore complex in the mammalian central neurons and, hence, increases the chloride conductance, which may contribute to anesthesia produced by the agent. The desensitization of the GABAA receptor in the presence of high concentrations of propofol may result in a suppression of the GABAA inhibitory system.
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Letter Clinical Trial
Jet venturi ventilation via the Bullard laryngoscope.