Alterations of Cerebral Vasoreactivity in Increased Intracranial Pressure

In our previous reports, we defined the following 4 stages according to changes in cerebral blood flow produced by increased intracranial pressure in dogs. Stage 1： The period of no significant changes in any parameters. Stage 2： The period in which only the cerebral blood flow begins to decrease. Stage 3-A： The period of vasopressor response preserving electrical activity in EEG. Stage 3-B： The period of vasopressor response after disappearance of EEG activity. Stage 4： The terminal stage. The present study was designed to investigate alterations of cerebral vasoreactivity in each stage and also to clarify the correlation between these alterations and brain damage during gradual increase in intracranial pressure. Mongrel dogs were anesthetized with pentobarbital sodium and measurements were performed on polygraph continuously; parameters were respiration, arterial blood pressure, cerebral blood flow (CBF, heat clearance method), cerebral blood volume (CBV, intravenous injection method), EEG, and intracranial pressure (ICP).