Regional brain blood flow regulation during orthostatic stress: New insights from volumetric brain blood flow measurements

摘要

The quotidian challenge of moving to the upright posture (orthostasis) requires rapid integration of numerous reflex mechanisms that preserve adequate brain perfusion and allow maintenance of the upright posture without fainting. These reflex adjustments include cardiovascular control mechanisms that, via adjustments to sympathetic outflow, modulate heart rate, vascular resistance, blood volume and blood pressure and ultimately cerebral blood flow (CBF). Adequate CBF is critical to maintain a constant supply of oxygen and nutrients to the metabolically active brain. It perhaps comes as no surprise that orthostatic intolerance and related symptoms of presyncope and syncope are fundamentally caused by a compromise to maintain adequate CBF.