Continuous measurement in neurocritical care of cerebral blood flow (CBF) calculated from ICP and central venous pressure

Abstract

The cerebral blood flow, CBF, is an important clinical parameter in neuro-intensive care. The possibility to continuously monitor CBF, computed from referential ICP, rICP (calculated from measured intracranial pressure, ICP, and central venous pressure, CVP) and venous outflow resistance, Rv, could importantly improve patient care. For the CBF(1) method the pulsative part of CBF (with rICP increase due to vascular volume increase) gives the venous outflow resistance, Rv. The CBF max method finds Rv from the close correlation between rICP and Rv. For both CBF(1) and CBF max, rICP divided with Rv gives CBF. The parameters rICP, Rv and CBF were calculated from measurements of ICP increase, and of intracerebral venous volume increase in nine subjects, by the CBF(1) method. The result, together with the finding of a close correlation between rICP and Rv, which made CBF dependent on rICP only, gave confirmation of the theory for computation of CBF, with two methods for continuous monitoring of CBF from rICP, one (CBF(1)) using the systolic ICP increase to find Rv, and one (CBF max) using the relationship between Rv and rICP at rICP exceeding about 10 mmHg in this study.