The Cerebral Circulation

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.

This Brief provides a comprehensive introduction to the control of blood flow in the brain. Beginning with the basic physiology of autoregulation, the author goes on to discuss measurement techniques, mathematical models, methods of analysis, and relevant clinical conditions, all within this single volume. The author draws together this disparate field, and lays the groundwork for future research directions. The text gives an up-to-date review of the state of the art in cerebral autoregulation, which is particularly relevant as cerebral autoregulation moves from the laboratory to the bedside. Cerebral Autoregulation will be useful to researchers in the physical sciences such as mathematical biology, medical physics, and biomedical engineering whose work is concerned with the brain. Researchers in the medical sciences and clinicians dealing with the brain and blood flow, as well as industry professionals developing techniques such as ultrasound, MRI, and CT will also find this Brief of interest.

Core Topics in Neuroanesthesia and Neurointensive Care is an authoritative and practical clinical text that offers clear diagnostic and management guidance for a wide range of neuroanesthesia and neurocritical care problems. With coverage of every aspect of the discipline by outstanding world experts, this should be the first book to which practitioners turn for easily accessible and definitive advice. Initial sections cover relevant anatomy, physiology and pharmacology, intraoperative and critical care monitoring and neuroimaging. These are followed by detailed sections covering all aspects of neuroanesthesia and neurointensive care in both adult and pediatric patients. The final chapter discusses ethical and legal issues. Each chapter delivers a state-of-the art review of clinical practice, including outcome data when available. Enhanced throughout with numerous clinical photographs and line drawings, this practical and accessible text is key reading for trainee and consultant anesthetists and critical care specialists.

Much of our knowledge of the cerebral circulation has been derived from studies of species other than human. There is increas ing recognition of species differences and concern that studies in animals may be misleading if unquestioningly applied to the human. A dramatic example of this occurred in the early his tory of the study of the circulation of the brain. Galen of Pergamo (131-201 AD) described a rete mirabile or "marvelous network" of blood vessels at the base of the human skull that he must have derived from observations of certain animals. This vascular structure was supplied by the carotid arteries which, after penetrating the cranium,"are divided into a large number of very small and thin branches in the region between the cranium and the dura matter. Then . . . intersecting one another they give the impression of having forgotten their way in the brain. But this is not the case. In fact, these numerous arteries rejoin and unite like the roots of a tree trunk. . . . " The authority of Galen's writings dominated scientific thought for about 1500 years. His description of a rete was unques tioned by Leonardo de Vinci, who included it in his anatomical sketches. William Harvey's remarkable observations led to his definitive account of the circulation of blood.

Biophysical Aspects of Cerebral Circulation provides a comprehensive review of the cerebral circulatory system. This book consists of four chapters. Chapter 1 is devoted to methodology attempts to explain the special features of a biophysical approach. The biophysical principles of the most commonly used modem methods such as the clearance method and rheoencephalography are described in detail. The second and third chapters examine all the biophysical aspects of the cerebral circulatory system as a functional unit and deal with some principles of its regulation. The results of systems analysis using mathematical modeling are presented in broad outline. Chapter 4 deals with processes related to the regional cerebral circulation. Such investigations focus mainly on the relationship between periodically fluctuating factors affecting limited areas of brain tissue. This text is beneficial to medical students and individuals researching on cerebral circulation.