View clinical trials related to Cerebral Blood Flow.
Filter by:The prevalence of cognitive impairment in maintenance hemodialysis (MHD) patients is 3 to 5 times higher than that in ordinary people, so it is essential to find the associated risk factors in this population. This project intends to evaluate whether changes in cerebral blood flow during dialysis have an impact on cognitive function in middle-aged and elderly MHD patients and clarify their influence on brain imaging characteristics. MHD patients who started hemodialysis at 3 to 6 months were selected to examine the difference in middle cerebral artery flow rate before and after dialysis by transcranial Doppler ultrasound to reflect the changes in cerebral blood flow. Changes in the cognitive function scale assessment (memory, executive function, and other five cognitive domains) and brain magnetic resonance imaging examinations are planned to collect both at baseline and after a one-year follow-up. Then the investigator used the multiple linear regression method to analyze the effects of the difference in middle cerebral artery flow on the changes in cognitive function and the characteristics in brain imaging. The investigators anticipate that the characteristics of the influence of changes in cerebral blood flow on cognitive impairment in Chinese MHD patients will be elucidated in this study, which may provide crucial clinical evidence for finding preventive and intervention measures for cognitive impairment in this group of population.
When astronauts return from space flight, they manifest a set of symptoms, the most striking of which is orthostatic intolerance, that is, the inability to stay upright. This orthostatic intolerance is related to cardiovascular adaptation and disappears in a few days, but the prospect of long-term space travel makes this maladaptation a major concern of space agencies, at a time when there is serious consideration to make " land "a ship on Mars. Previous studies suggest that brain vessel adaptation may contribute to spatial post-flight orthostatic intolerance. The question remains controversial because not all studies are consistent. These studies are all based on the measurement of blood flow in a single artery of the brain (the average cerebral, see cerebral circulation diagram) easily accessible with a Doppler ultrasound machine. Our team has good reason to believe that the adaptation of the cerebral vessels is not carried out in the same way in all the arteries of the brain and that in particular the arteries that irrigate the posterior and inferior parts of the brain are a major determinant. from cerebrovascular adaptation to orthostatism and that orthostatic intolerance is more specifically related to a decrease in blood flow in these arteries. On the other hand our team has shown that the external carotid artery plays, under certain conditions, a buffer role of the sudden variations of perfusion pressure of the brain. During the weightless phase of parabolic flight, part of the blood from the legs and abdomen "rises" to the thorax and this transfer of fluid induces changes in blood pressure and cardiac output that affect the cerebral circulation. From a cardiovascular point of view, it is the same thing for a seated subject to lie down, but the parabolic flight offers the unique possibility of achieving this transfer in a fraction of a second and thus allowing to study the immediate response of the cerebral circulation. . Investigators goal is therefore to quantify the changes in blood flow in the posterior and anterior territories of the brain (transcranial ultrasound) as well as in the internal carotid and vertebral (Doppler ultrasound) during changes in blood pressure and cardiac output induced by transfers. liquid resources associated with the transition to weightlessness. The oxidative stress generated by weightlessness has been identified as a determining factor in cerebrovascular deconditioning associated with orthostatic intolerance. In order to quantify the biochemical markers of this stress, a venous sample will be taken before and just after the parabolic flight.