Influence of shear rate on platelet aggregation in cerebral microvessels

The aggregation of platelets in injured cerebral arterioles was delayed as the wall shear rate rose, over a range of 0.2 to 1.4 sec^-1. The shear rates were calculated from centerline velocities determined with the two-slit technique and a cross correlator. The velocity range was 2 to 13 mm/sec. The correlation between aggregation latency and shear rate was 0.44, P < 0.02, and 0.55, P < 0.05, in each of two studies. The correlation between aggregation latency and centerline velocity was slightly less and was slightly less significant than the correlation between shear rate and aggregation latency.