[Effect of an increase in intracranial pressure on transvascular fluid movement in the brain]

Transvascular fluid exchange was studied in the haemodynamically isolated brain in the hermetically closed cranium. The brain was perfused with the constant blood flow under the condition of the cross-perfusion from anesthetized donor-cats. The rise of the intracranial pressure was accompanied by the liquor resorption and increasing of venous outflow. The velocity of this process was proportional to the pressure increase. Changes of transmural vascular pressure were limited by the upstream vascular pressure elevation caused by the compression of the veins in the points of entry into the sagittal sinuses (the thin-walled cerebral veins and lacunae). Another mechanism preventing the shifts of the transmural vascular pressure, was augmentation of the fluid resorption. The role of these mechanisms in compensation of the transmural vascular pressure shifts during orthostatic loads, is discussed.