Measured turbulence and its effect on thrombus formation.

Turbulence is one of the hydraulic disturbances implicated in thrombus formation, even though absolute proof of its contributory effect is lacking. Because of the importance of a possible effect of turbulence on thrombus formation, the relation was studied in eight dogs. In each dog, two arteriovenous shunts were established, one from each femoral artery to the contralateral femoral vein. Only one shunt contained a turbulence-producing device; otherwise, the shunts were identical in shape, size, and material. The intensity of turbulence distal to the turbulence generator was quantified in vitro by measuring the relative magnitude of the randomly fluctuating velocities. In each of the eight dogs, more thrombi, by weight, accumulated in the turbulent shunt than in the laminar shunt (P < 0.001). Thrombi from the turbulent shunt weighed 180 ± 30 (SE) mg, whereas those from the laminar shunt weighed 0.9 ± 0.6 mg. The weight of thrombi that accumulated within the turbulent system appeared to be related to the intensity of turbulence. A linear relation was observed between the Reynolds number in the region of the turbulence-producing orifice and the weight of the thrombi within the turbulent shunt (r 0.90). The relative intensity and the absolute intensity of turbulence distal to the turbulence generator were also linearly related to the Reynolds number (r = 0.97 and 0.90, respectively). The results of this study therefore indicate that turbulence is a characteristic of blood flow that can contribute to the formation of thrombi.