The adult brain weighs about 1350 grams which 2% of total body weight. It receives 12-15% of cardiac output. At rest, CMRO2 is 3.5 ml O2 /100gms of brain tissue. Auto Regulation refers to the intrinsic capacity of the cerebral circulation to adjust its resistance to maintain cerebral blood flow constant over a side range of mean Arterial pressure (MAP). In normal persons, the limits of auto regulations are 50 and 150 mm Hg. Above and below this range, CBF is pressure dependent (pressure passive ) and varies linearly with Cerebral Perfusion Pressure (CPP).
Auto Regulation is influenced by various pathological processes and in addition to the time course over which CPP changes over. The precise mechanism by which auto Regulation is accomplished is unknown. It appears to be an intrinsic characteristic of cerebrovascular smooth muscle. PaCO2 and Regulation of cerebral blood flow. CBF…
