A new rheological method to measure fluidity change of blood during coagulation : application to in vitro evaluation of anticoagulability of artificial materials.

In order to attempt in vitro evaluation of antithrombogenecity for materials of artificial blood vessel tube, a new type of rheometer was developed. The rheometer originally consists of a cylindrical tube suspended from a torsion wire and filled with blood. The tube is excited in torsional oscillation and subsequent damped oscillation is observed. The apparatus can sensitively follow the change of fluidity during coagulation of blood. The damped oscillation curves during coagulation for fibrinogen - thrombin solution and blood put in a cylindrical tube made of the artificial material were measured. For fibrinogen - thrombin solution with lower fibrinogen and thrombin concentrations, the values of logarithmic damping factor (LDF) during coagulation increased and then decreased through a maximum. For blood and fibrinogen-thrombin solution with the higher concentrations of fibrinogen and thrombin, LDF monotonously decreased with the progress of coagulation. With a glass tube, the decrease of LDF for whole blood taken without anticoagulant rapidly occurred within about 15 min after sampling, while, with expanded polytetrafluoroethylene (EPTFE; Goar tex) and polydimethylsiloxane (Silastic) tubes, the decrease of LDF proceeds over 40-60 min. The present method is probably available for in vitro evaluation of anticoagulability or antithrombogenecity of artificial materials.