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Brain vascular and hydrodynamic physiology.

Protecting the brain in vulnerable infants undergoing surgery is a central aspect of perioperative care. Understanding the link between blood flow, oxygen delivery, and oxygen consumption leads to a more informed approach to bedside care. In some cases, we need to consider how high we can let the partial pressure of carbon dioxide go before we have concerns about risk of increased cerebral blood volume and change in intracranial hydrodynamics. Alternatively, in almost all such cases, we have to address the question of how low can we let the blood pressure drop before we should be concerned about brain perfusion. This review provides a basic understanding of brain bioenergetics, hemodynamics, hydrodynamics, autoregulation, and vascular homeostasis to changes in blood gases, which is fundamental to our thinking about bedside care and monitoring.