ABSTRACT
CVR refers to the capacity of the brain to increase cerebral blood volume (CBV) to maintain a constant CBF in the face of low cerebral perfusion pressure (CPP). Regional cerebral blood flow is determined by the ratio of CPP to cerebrovascular resistance by the formula:
CBF CPP/vascular resistance
Cerebral perfusion pressure is related to systemic MAP and intracranial pressure (ICP) by the equation:
CPP MAP – ICP
In healthy individuals, a constant CBF is maintained over a wide range of CPP, with mean CBF values approximately 50 ml/100 g/min (Figure 10.1). When CBF values fall below 20 ml/100 g/min, ischemia ensues. Infarction occurs at CBF levels 10-15 ml/100 g/min.
