Pathophysiological studies in the rat cerebral embolization model: measurement of epidural pressure and evaluation of tissue pH and ATP.

A rat embolization model was produced by occlusion of the main cerebral artery with a silicone cylinder embolus. Intracranial pressure was monitored by changes in epidural pressure (EDP), which was recorded by our designed flaccid microballoon. EDP changes could be divided into the two types: the first was moderate elevation, less than 20 mm Hg and the second was prominent, more than 20 mm Hg. Brain tissue pH on the embolized side showed heterogeneous changes composed of acidotic and alkalotic areas. Alkalotic change was frequently seen at the deep cerebrum which might be the result of plasma exudation due to disruption of blood-brain barrier (BBB). The degree of the EDP elevation was positively correlated with the extension of alkalotic area. Energy metabolism was also mainly disturbed in the deep cerebrum, but did not completely correspond to the pH change of the area. These results would indicate that embolization of the main cerebral artery could induce severe ischaemic insult on the deep cerebrum with massive brain swelling due to an early disruption of BBB.