Local cerebral blood flow in the recovery period following complete cerebral ischemia in the rat.

This study examines reflow patterns in the recirculation period following complete, global ischemia. Cerebrospinal fluid (CSF) compression ischemia was induced in ventilated rats for 5-30 min, and local cerebral blood flow (CBF) was measured autoradiographically after 5, 60, and 90 min of recirculation. Ischemia of 15 min duration was induced by four-vessel occlusion combined with arterial hypotension in two additional groups, with recovery periods of 5 or 60 min. In the immediate recirculation period (5 min), following 15 min of ischemia, local CBF was markedly heterogeneous. Thus, whereas most structures gave clear evidence of "reactive hyperemia," others showed perfusion defects of the "no-reflow" type. Typically these defects affected the striatum, thalamus, and hippocampus, as well as the frontal, sensorimotor, and parietal cortices. Areas of no-reflow appeared after 10 min, were more extensive after 15 min, and occupied a major part of the brain after 30 min of ischemia. When recirculation was instituted for 60 or 90 min, following 15 min of ischemia, flow returned in previously unperfused areas. However, a delayed hypoperfusion developed, which differed widely between structures (range of CBF values, 20-80% of control). When the ischemic period was prolonged to 30 min, some perfusion defects remained, even after 90 min of recirculation.