Abstract

Abstract The cerebral effects of bilateral carotid artery ligation were studied in ligthly anesthetized rats, either alone or combined with moderate reductions in the mean arterial blood pressure. The relative decreases in cerebral blood flow were estimated from the a‐v differences for O 2 and CO 2 on the assumption of an unchanged cerebral metabolic rate. Ligation of the carotid arteries alone was found to decrease cerebral blood flow to about 50 % of normal, but to give no significant changes in the energy state of the tissue, as judged from the tissue contents of the ATP, ADP and AMP. When the cerebral blood flow was reduced further by means of an induced decrease in blood pressure, the energy state of the tissue was severely affected. At this point the cerebral venous Po 2 was reduced from about 50 to about 30 mm Hg. Since pure hypoxemia with a reduction of venous Po 2 to about 10 mm Hg can be tolerated without changes in the energy state of the tissue, it is concluded that ischemia may lead to a grossly inhomogenous reduction in the tissue perfusion.