Effects of Cerebral Venous and Cerebrospinal Fluid Pressure on Cerebral Blood Flow

Abstract

Regional cerebral blood flow responses to elevated jugular venous or cerebrospinal fluid pressure (Pcsf) were measured in thirty-nine anaesthetized ventilated dogs. When jugular venous pressure was elevated, arterial blood pressure and Pcsf were maintained constant at control values. When Pcsf was elevated, arterial and jugular venous pressure were maintained constant at control values. Cerebral perfusion pressure was calculated as the difference between arterial pressure and Pcsf, or jugular venous pressure, whichever downstream pressure was the highest. With an elevation in Pcsf or jugular venous pressure, the cerebral circulation autoregulated and no alterations in cerebral blood flow occurred as long as perfusion pressure remained above 60 mm Hg. When cerebral perfusion pressure decreased to values below 60 mm Hg, cerebral blood flow decreased significantly. We conclude that the brain autoregulates its blood flow to changes in perfusion pressure. In addition, our results suggest that the dominant mechanism of cerebral autoregulation is metabolic, not myogenic.