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BACKGROUND Anesthetic agents, especially volatile anesthetics and nitrous oxide (N2O), are suspected to perturb cerebral homeostasis and vascular reactivity. The authors quantified the effects of sevoflurane and propofol as sole anesthetics and in combination with N2O on regional cerebral blood flow (rCBF), metabolic rate of oxygen (rCMRO2), and blood(More)
BACKGROUND Animal experiments have demonstrated neuroprotection by ketamine. However, because of its propensity to increase cerebral blood flow, metabolism, and intracranial pressure, its use in neurosurgery or trauma patients has been questioned. METHODS 15O-labeled water, oxygen, and carbon monoxide were used as positron emission tomography tracers to(More)
BACKGROUND The authors report a positron emission tomography (PET) study on humans with parallel exploration of the dose-dependent effects of an intravenous (propofol) and a volatile (sevoflurane) anesthetic agent on regional cerebral blood flow (rCBF) using quantitative and relative (Statistical Parametric Mapping [SPM]) analysis. METHODS Using(More)
The purpose of this study was to compare the applicability of four different measures of heart rate variability (HRV) in the assessment of cardiac vagal outflow, with special reference to the effect of breathing pattern. The anticholinergic effects of an intravenous glycopyrrolate infusion (5 microg x kg(-1) x h(-1) for 2 h) during spontaneous and(More)
BACKGROUND Animal studies have demonstrated neuroprotective properties of S-ketamine, but its effects on cerebral blood flow (CBF), metabolic rate of oxygen (CMRO2), and glucose metabolic rate (GMR) have not been comprehensively studied in humans. METHODS Positron emission tomography was used to quantify CBF and CMRO2 in eight healthy male volunteers(More)
One of the greatest challenges of modern neuroscience is to discover the neural mechanisms of consciousness and to explain how they produce the conscious state. We sought the underlying neural substrate of human consciousness by manipulating the level of consciousness in volunteers with anesthetic agents and visualizing the resultant changes in brain(More)
Anesthetic-induced changes in the neural activity of the brain have been recently utilized as a research model to investigate the neural mechanisms of phenomenal consciousness. However, the anesthesiologic definition of consciousness as "responsiveness to the environment" seems to sidestep the possibility that an unresponsive individual may have subjective(More)
OBJECTIVE To investigate EEG effects of three escalating concentrations of sevoflurane and propofol in single-agent anesthesia on healthy subjects. METHODS Four-channel EEG was continuously recorded at 1, 1.5, and 2 minimum alveolar concentration (MAC)/effective plasma concentration 50 (EC50) levels of either sevoflurane or propofol anesthesia in 16 men,(More)
BACKGROUND Dexmedetomidine is a new potent and highly selective alpha 2-adrenoceptor agonist with sedative-hypnotic and anesthetic sparing properties. Because of its sympathoinhibitory activity, it may prove useful in balancing the cardiostimulatory effects and attenuating the adverse central nervous system effects of ketamine. METHODS A double-blind,(More)
RATIONALE The noncompetitive glutamate N-methyl-D: -aspartate receptor antagonist ketamine induces transient psychotic symptoms in man. Involvement of dopaminergic mechanisms in these effects has been suggested. OBJECTIVES The purpose of this article is to study the effects of ketamine on extrastriatal dopamine receptor availability in healthy subjects(More)