The regulation of cerebral blood circulation in subclavian steal syndrome.

Blood flow to the brain was studied in 11 patients suffering from subclavian steal syndrome. The venous isotope-dilution method was used to measure total blood flow to the brain and the dye-dilution method with intravenous administration of 50 mg of Evans blue was used to determine cardiac output. Cerebral blood flow was significantly lower in the 11 patients with subclavian steal syndrome than in the control group, and the 02 consumption of the brain was low, cerebral resistance was elevated, and the cerebral fraction of the cardiac output was decreased in comparison with the controls. The effect of occlusion of the ipsilateral brachial artery was studied in 10 of the patients with subelavian steal syndrome. The cerebral blood flow and the cerebral fraction of the cardiac output increased significantly as a result of the occlusion in these patients. Studies on three patients after surgical correction of the lesion in the subclavian artery showed significant improvement in the cerebral circulation.