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Das vorliegende Buch enth{lt die Beitr{ge eines internatio- nalen Symposiumszum Thema "Stimulierte Hirndurchblutung". Vorgestellt werden zun{chst neue Erkenntnisse zur Regulation der Hinrdurchblutung. Im 2. Abschnitt kommen verschiedene Methoden zur Messung der Hirndurchblutung zur Sprache, die sowohl unter experimentellen als auch unter klinischen Be- dingungengetestet wurden. Es folgt ein Abschnitt, der ver- schiedene M|glichkeiten zur Stimulation der Hirndurchblutung aufzeigt. Im letzten Abschnitt wird aufdie Bedeutung der stimulierten Hirndurchblutungsmessung zur Bestimmung der ce- rebrovascul{ren Reservekapazit{ten hingewiesen. Dieser Para- meter hat nach den vorliegenden Untersuchungen klinisch- praktische Bedeutung, beispielsweise f}r die Indikations- stellung bei cerebrovascul{ren Eingriffen zur Isch{mie-Pro- phylaxe.
This e-book will review special features of the cerebral circulation and how they contribute to the physiology of the brain. It describes structural and functional properties of the cerebral circulation that are unique to the brain, an organ with high metabolic demands and the need for tight water and ion homeostasis. Autoregulation is pronounced in the brain, with myogenic, metabolic and neurogenic mechanisms contributing to maintain relatively constant blood flow during both increases and decreases in pressure. In addition, unlike peripheral organs where the majority of vascular resistance resides in small arteries and arterioles, large extracranial and intracranial arteries contribute significantly to vascular resistance in the brain. The prominent role of large arteries in cerebrovascular resistance helps maintain blood flow and protect downstream vessels during changes in perfusion pressure. The cerebral endothelium is also unique in that its barrier properties are in some way more like epithelium than endothelium in the periphery. The cerebral endothelium, known as the blood-brain barrier, has specialized tight junctions that do not allow ions to pass freely and has very low hydraulic conductivity and transcellular transport. This special configuration modifies Starling's forces in the brain microcirculation such that ions retained in the vascular lumen oppose water movement due to hydrostatic pressure. Tight water regulation is necessary in the brain because it has limited capacity for expansion within the skull. Increased intracranial pressure due to vasogenic edema can cause severe neurologic complications and death.
Proceedings from a meeting on stimulated cerebral blood flow.
There are lots of dynamic process exist co-currently and spontaneously when the neurons in the brain are activated by the external stimulation, like cerebral blood flow (CBF) change, oxygen extraction change. The study of the dynamic relationship among these physiological variables, which describe the brain activity through different aspects, can help people understand the brain function when it gets excited and researchers can interpret the physiological meaning of these parameters better. The most common functional magnetic resonance imaging techniques are BOLD and ASL fMRI, in this research, the correlation between these two methods has been studied through a simultaneous data acquisition strategy. Assessing such correlation between BOLD fMRI measures and CBF offers a link of these two to the underlying of the spontaneous brain activities. In the study, an ASL pulse sequence PICORE has been used to perform the fMRI experiment on 7 health subjects. A rapid median nerve electrical stimulation paradigm has been used to detect the activation of the brain from seven normal health right-handed human subjects. Three ROIs (SMA, S1, M1) have been selected and the data were analyzed to investigate the correlation between CBF value and BOLD signal change during brain activities. We found the CBF value rises for 5 - 6 ml/min/100g for fixed ROI and 11 - 12 ml/min/100g for non-fixed ROI and the BOLD signal change was around 0.8% for both situations. Our results shows for a fixed size ROI of each individual subject, no significant difference has been found for CBF value difference and the BOLD signal change between different runs and neither did the ratio of these two parameters (p > 0.05). When studied the activation area size for each run, we found significant difference for both CBF value difference and BOLD signal change (p
Until recently, monitoring of cerebral blood flow and metabolism was an unattained goal. Determination of cerebral blood flow was limited to intermittent measurements and particularly difficult to perform in critically ill patients. Meanwhile there are techniques available, however, to monitor cerebral blood flow and cerebral oxygenation, both globally and regionally. Therefore we thought it worthwhile to discuss these new continuous techniques and to compare them with well-known techniques which discontinuously measure CBF. For that purpose, an international workshop with some leading experts in the field was held in October 1992 in Berlin. The workshop consisted of about 20 lectures, either reviews on a special topic, or latest results. These contributions were given by invitation and were extensively discussed. Unfortunately it is impossible to reproduce the discussions. On the other hand, all speakers delivered a manuscript promptly after the meeting so that we were able to edit them within a short time. Since monitoring of cerebral blood flow in intensive care is a rapidly growing and changing topic, the written contributions should be quickly available. Authors, editors and publishers have tried to come close to this ideal. As editors we would like to thank the authors and the publishers who enabled us to come out with this volume of the proceedings as early as possible.