Direct visualization of trapped erythrocytes in rat brain after focal ischemia and reperfusion.

Partial microcirculatory stasis after cerebral ischemia and reperfusion is a potential factor in delayed cell death. Sometimes described as the "no-reflow" phenomenon, limitations in current detection techniques have left the extent and spatial distribution of the phenomenon undetermined, which has led to some doubt as to its actual existence. The authors describe a new method, based on erythrocyte autofluorescence, that allows the erythrocytes trapped in the microvasculature, and thus blocking recirculation, to be directly visualized. Using this method, the authors have examined the spatial and temporal characteristics of this phenomenon in the rat intraluminal model of cerebral ischemia and reperfusion. Up to 15% of the capillaries in the ischemic penumbra remained occluded at least 2 hours after reperfusion. The amount of capillary bed showing trapped erythrocytes was more severe in the ischemic penumbra region than in the ischemic core. These results indicate that the no-reflow phenomenon may contribute to the developing damage in ischemic penumbra region, leading to additional injury after reperfusion.