Volume Pressure Curves and Pial Vascular Pressure Gradients in the Rhesus Monkey

Abstract

The volume pressure relationships (VPR) within the cranial cavity is of fundamental importance in understanding the mechanisms of brain damage in a variety of conditions. The conventional teaching concerning the VPR under conditions of increasing intracranial pressure (ICP) is that the relationship is smoothly exponential after a brief period of volume increase without significant pressure rise (1). Two years ago we presented data which showed that departures from such an idealized exponential curve are the rule if the factor of rate of mass expansion is considered. We also discovered a critical rate for continuous expansion of an extradural supratentorial mass below which a vasopressor response was not very prominent thereby markedly affecting the shape of the VPR (2). Thus, brain death (as recognized by fixed dilated pupils and an isoelectric EEG) was produced at relatively low levels of ICP.