Effects of acute occlusion of superior cava on cerebral circulation were studied in dogs, Following results were obtained. 1) Pressure of intracranial vein rose up to 2.5 times of control level in average on occlusion of superior vena cava at the point distal to azygos vein and then showed gradual decline within 70 to 90 minutes.
On the contrary, it rose np to 4 to 8 times of control level on occlusion of superior vena cava inclu ling azygos vein and it remained at the same level during observation of two hours. Some of experimental animals died during occlusion. 2) Good correlation was found betweeu intraspinal pressure and that of intracranial vein on occlusion of superior vena cava. 3) Decrease of blood flow to brain was compensated by increase of arterio-venous oxygen difference on occlusion of superior vena cava at the point distal to azygos vein. Hence, decrease of oxygen consumption of brain tissue was not significant. 4) Marked decrease in oxygen and glucose consumption of brain tissue developed 30 minutes after occlusion of superior vena cava including azygos vein, suggesting of development of impending damage of brain tissue.