Basic studies on the effects of stenotic connectors on mechanical blood hemolysis

In order to obtain fundamental data on the effects of inner shapes of connectors on blood, in vitro hemolysis tests were performed by using an original designed extracorporeal circuit. Several types of stenotic connectors were made, and each piece was incorporated in each identical circuit. Then, heparinized fresh calf blood was infused into each circuit and was circulated by the centrifugal pump. In this comparative study, changes in plasma free hemoglobin in each circuit were obtained as a function of the pumping time of up to 6 hours. A brief summary of the results are as follows: 1) The connector could achieve a low hemolysis condition if there was an inlet taper of 20 degrees, or a leading edge of only R = 0.5 mm. 2) A suface roughness (Ra) might be a great factor to the hemolysis, because hemolysis level on the Ra of 1.35 μm produced by six times as compared with that on the Ra of 0.54 μm. 3) Even if a connector had an abrupt stenosis with smooth surface (Ra = 0.54 μm), the hemolysis was kept low.