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Spontaneous baroreflex function can be altered by acute changes in central blood volume. Both a reduction in spontaneous baroreflex function at central hypovolemia and augmentation at hypervolemia suggest a dose-effect relationship between central blood volume and spontaneous baroreflex function. However, this relationship has not been quantified over(More)
BACKGROUND Humans encounter increased partial pressures of inspired oxygen in some kinds of diving as well as during use of hyperoxic mixtures to shorten decompression times and hyperbaric oxygen therapy for decompression sickness or other clinical conditions. Although it is known that hyperoxia may affect cardiovascular regulation, such effects are(More)
BACKGROUND Frequent changes in the perioperative central blood volume could affect cerebral autoregulation through alterations in sympathetic nerve activity, cardiac output, blood viscosity, and cerebral vasomotor tone. However, the effect of dynamic cerebral autoregulation has not been studied during acute wide-ranging changes in central blood volume,(More)
BACKGROUND Although midazolam and propofol reduce cerebral blood flow (CBF) similarly, they generate different effects on the autonomic nervous system and endothelium-induced relaxation. Midazolam induces sympathetic dominance, whereas propofol induces parasympathetic dominance. Midazolam has no effect on endothelium-dependent relaxation, whereas propofol(More)
Cerebral blood flow (CBF) increases and dynamic cerebral autoregulation is impaired by acute hypoxia. We hypothesized that progressive hypocapnia with restoration of arterial oxygen content after altitude acclimatization would normalize CBF and dynamic cerebral autoregulation. To test this hypothesis, dynamic cerebral autoregulation was examined by spectral(More)
STUDY OBJECTIVE To evaluate the different effects on autonomic circulatory control during volatile induction/maintenance of anesthesia (VIMA) vs total intravenous anesthesia (TIVA). DESIGN Prospective study. SETTING Operating theater of a university hospital. PATIENTS Twenty patients, with American Society of Anesthesiologists physical status of I or(More)
Acute hypoxia directly causes cerebral arteriole vasodilation and also stimulates peripheral chemoreceptors to change autonomic neural activity. These changes may alter cerebral vascular modulation. We therefore hypothesized that dynamic cerebral autoregulation would be altered during acute exposure to hypoxia. Fifteen healthy men were examined under(More)
INTRODUCTION Hyperoxia is reported to decrease steady-state cerebral blood flow (CBF). In addition, dynamic cerebral autoregulation would be altered. Hyperoxia may improve dynamic cerebral autoregulation, contrary to hypoxia. However, no previous studies have examined changes in steady-state CBF velocity (CBFV) and alterations of dynamic cerebral(More)
INTRODUCTION The classical view states that hypoxia beyond an oxygen concentration of about 17% induces tachycardia. However, few studies have investigated the dose-dependent effects of acute normobaric hypoxia on autonomic nervous regulation of the cardiovascular system. Therefore, we evaluated the effects of stepwise hypoxia on cardiovascular neural(More)
PURPOSE The α(2)-adrenergic receptor agonist dexmedetomidine reportedly weakens heart rate (HR) responses to 'rapid' (during a few seconds) reduction in arterial pressure, but does not affect HR responses to 'gradual' (during 60 s) reduction in arterial pressure. As the speed of neurotransmission along the parasympathetic nerve is relatively rapid,(More)