Sequential studies of severely hypometabolic tissue volumes after permanent XXXX . A positron emission tomographic investigation in anesthetized @entity6599 .

@entity1 @entity1009 @entity2500 @entity26 @entity3474 @entity6599 @entity1188
BACKGROUND AND PURPOSE: In the positron emission tomography literature, markedly hypometabolic brain tissue ( @entity26 metabolism < 1.3 to 1.7 mL.100 g-1. @entity1009 ) has often been equated with irreversible damage in the @entity1 brain. By serial positron emission tomography measurements, we investigated the temporal evolution of the volume of severely hypometabolic brain tissue after permanent @entity2500 in anesthetized @entity6599 with, as a perspective, the development of rational therapeutic strategies. METHODS: Seven anesthetized and ventilated @entity6599 underwent sequential positron emission tomography examinations with the 15O steady-state technique before and 1, 4, 7, and 24 hours and 14 to 29 days after occlusion. In each @entity3474 the @entity1188 volume was calculated by quantitative histological procedures after 19 to 41 days of occlusion. RESULTS: The sequential measurement of regional @entity26 metabolism demonstrated an extension (for > or = 24 hours) of the volume of severely hypometabolic tissue as defined by both absolute and relative metabolic thresholds, and this profile of evolutivity is observed no matter the threshold used. Mean (+/- SEM) @entity1188 volume of 2.4 +/- 0.6 cm3 was comparable to a tissue volume with @entity26 consumption < 40% of contralateral metabolism. The volume of hypometabolic tissue was essentially stable at the 1-, 4-, and 7-hour postocclusion studies, increased markedly at the 24-hour study point, and increased even further in the chronic-stage study (on average, 17 days after occlusion). The tissue that eventually displayed a severely hypometabolic state at the final measurement showed a significant decrease of @entity26 metabolism and cerebral blood flow at each time analyzed. In that tissue, the @entity26 extraction fraction increased significantly at 1 hour (although not thereafter). CONCLUSIONS: The extension of severely hypometabolic volume after @entity2500 reinforces the concept of a dynamic penumbra and suggests the existence of a relatively large window of therapeutic opportunity in which it may be possible to develop neuroprotective strategies. Our study suggests that maximum @entity1188 volume is determined at some time between 24 hours and 17 days after permanent @entity2500 in anesthetized @entity6599 .
