The time course of changes in cerebral intravascular volume after single and repeated carotid artery occlusions was evaluated in the gerbil, and compared with the characteristic patterns of postischemic edema and cerebral blood flow. The time course of blood volume was similar after single and repeated occlusions and correlated well with blood flow changes previously described. A 50% reduction in vascular volume was associated with the interval of postischemic hypoperfusion which lasts for several hours following release of occlusion. Both blood volume and blood flow had returned to control at the time of severe secondary edema 24 hours after repeated occlusions, at which time there is morphological evidence of microvascular compression. These results indicate that decreases in blood flow and blood volume reflect primarily the constriction of larger vessels, and that values in the normal range may be observed even under conditions of severe edema and impaired perfusion at the capillary level.
