Platelet activation and erythrocyte aggregation rate in patients with cerebral infarction

Whole Blood Viscosity and Cerebral Blood Flow in Acute Ischemic Stroke

Existing effective treatments for ischemic stroke restore blood supply to the ischemic region using thrombolysis or mechanical removal of clot. However, it is increasingly recognized that successful removal of occlusive thrombus from the large artery-recanalization, may not always be accompanied by successful restoration of blood flow to the downstream tissues-reperfusion. Ultimately, brain tissue survival depends on cerebral perfusion, and a functioning microcirculation. Because capillary diameter is often equal to or smaller than an erythrocyte, microcirculation is largely dependent on erythrocyte rheological (hemorheological) factors such as whole blood viscosity (WBV). Several studies in the past have demonstrated elevated WBV in stroke compared with healthy controls. Also, elevated WBV has shown to be an independent risk factor for stroke. Elevated WBV leads to endothelial dysfunction, decreases nitric oxide-dependent flow-mediated vasodilation, and promotes hemostatic alterations/thrombosis, all leading to microcirculation sludging. Compromised microcirculation further leads to decreased cerebral perfusion. Hence, modulating WBV through pharmacological agents might be beneficial to improve cerebral perfusion in stroke. This review discusses the effect of elevated WBV on endothelial function, hemostatic alterations, and thrombosis leading to reduced cerebral perfusion in stroke.

Ischemic preconditioning reduces peripheral oxidative damage associated with brain ischemia in rats

Brain ischemia followed by reperfusion causes neuronal death related to oxidative damage. Furthermore, it has been reported that subjects suffering from ischemic cerebrovascular disorders exhibit changes in circulating platelet aggregation, a characteristic that might be important for their clinical outcome. In the present investigation we studied tert-butyl hydroperoxide-initiated plasma chemiluminescence and thiol content as measures of peripheral oxidative damage in naive and preconditioned rats submitted to forebrain ischemia produced by the 4-vessel occlusion method. Rats were submitted to 2 or 10 min of global transient forebrain ischemia followed by 60 min or 1, 2, 5, 10 or 30 days of reperfusion. Preconditioned rats were submitted to a 10-min ischemic episode 1 day after a 2-min ischemic event (2 + 10 min), followed by 60 min or 1 or 2 days of reperfusion. It has been demonstrated that such preconditioning protects against neuronal death in rats and gerbils submitted to a lethal (10 min) ischemic episode. The results show that both 2 and 10 min of ischemia cause an increase of plasma chemiluminescence when compared to control and sham rats. In the 2-min ischemic group, the effect was not present after reperfusion. In the 10-min ischemic group, the increase was present up to 1 day after recirculation and values returned to control levels after 2 days. However, rats preconditioned to ischemia (2 + 10 min) and reperfusion showed no differences in plasma chemiluminescence when compared to controls. We also analyzed plasma thiol content since it has been described that sulfhydryl (SH) groups significantly contribute to the antioxidant capacity of plasma. There was a significant decrease of plasma thiol content after 2, 10 and 2 + 10 min of ischemia followed by reperfusion when compared to controls. We conclude that ischemia may cause, along with brain oxidative damage and cell death, a peripheral oxidative damage that is reduced by the preconditioning phenomenon.