Correlation between brain blood flow and endothelial changes following a double subarachnoid hemorrhage method

While a wide array of pathological changes occur in cerebral arteries following subarachnoid hemorrhage (SAH), the most consistent is endothelial damage. Since endothelium normally modulates reflexes that influence vascular tone, damage to it may represent a significant contributor to cerebral vasospasm following SAH. Changes in cerebellar blood flow (CBF) and damage to cerebral arteries were studied in rats. Each animal was subjected to a SAH followed by a second hemorrhage three days later. Each SAH was produced by the subarachnoid injection of either 0.3 ml of isotonic saline (N=22) or 0.3 ml of whole blood (N=22). All studies were made at various intervals after the second SAH. In the saline injected group, CBF remained unchanged over a 10 day period and no cerebral vascular pathology was observed. In contrast, the injection of blood produced significant changes in both CBF and in cerebral arteries. By 30 minutes post-blood injection, CBF became significantly decreased and remained that way for 3 days. By the 10th day, however, it had returned to control values. Endothelial injury was observed in cerebral arteries from 30 minutes through 3 days, the same period during which CBF was significantly reduced. By 10 days, the time period in which CBF had rebounded to control ranges, cerebral arteries showed no evidence of endothelial damage and resembled control cells. The results indicate a direct correlation between changes in CBF and endothelial injury in the early stage following SAH. The double-SAH procedure in rats may also represent a usable small animal model for studying chronic vasospasm following SAH.