Cerebral Blood Flow (CBF) The normal cerebral blood flow is
approximately 50ml/100g/min or 700 ml/min, which is roughly 14 %
of the cardiac output. This ranges from 20ml/100g/min in white
matter to 70ml/100g/min in grey matter. The Kety-Schmidt
technique applies the Fick principal using N2O to calculate
whole brain CBF. Cerebral Blood Flow = Cerebral Perfusion
Pressure / Cerebrovascular resistance Cerebral Perfusion
Pressure CPP = CBF X CVR (Compare BP = CO X SVR) Cerebral
perfusion pressure (CPP) is defined as the difference between
mean arterial pressure (MAP) and intracranial (ICP) or central
venous pressures (CVP), whichever is the highest. MAP is the
diastolic pressure plus one third of the pulse pressure
(difference between the systolic and diastolic). CPP = MAP – ICP
(or CVP, whichever is the highest) A CPP less than 70 mmHg can
lead to a rapid decrease in jugular venous bulb saturation
(normal range 65%-75%) because of increased oxygen extraction A
number of studies on patients with severe head injuri