Variations in Pressure Volume Index and CSF Outflow Resistance Measured at Different Places in the Craniospinal Axis

Abstract

The early detection of intracranial complications and prediction of cerebral herniation are prime purposes of ICP monitoring. The most reliable index of the risk of herniation is the estimation of the capacity of intracranial compensatory mechanism provided by the pressure volume index (PVI). This is usually determined by bolus injection test into the lateral ventricle. Bolus injection into the lateral ventricle, however, is not always possible in critically ill patients. It is not a rare experience that catheterization of the lateral ventricles is difficult when they are collapsed by mass lesions or brain swelling, and ICP monitoring must be conducted from the brain surface. This is a serious problem, because estimation of the volume pressure relationship is impossible in just those patients in whom such information is most urgently required. It would be useful to know whether bolus injection into the subarachnoid space yielded the same results as in the lateral ventricle.