A Study of Clot Firmness in Viscometer Tubes

Abstract

Determinations of clot firmness have been made by studying the tensile strength of clots. Fonio 1 prepared plasma clots with magnesium sulfate solution and ether. He pressed the clots into discs, suspended them, and determined their tensile strength. Kristenson 2 who criticized this method used clots from plasma which was prepared by centrifugation in ice jackets. Following incubation at 37° C. for 1 hour he wrapped both ends of the coagulum in linen cloth and tied a string around each end. He then measured the tensile strength by adding weights until the clot tore. Schnedorf 3 permitted blood to coagulate around two wire meshes which served as points of attachment. Five to 30 minutes after coagulation at room temperature, weights were added to measure the tensile strength. By employing different amounts of blood and using several modifications of the same principle, he was unable to obtain comparable results. To test clot firmness we constructed a viscometer tube which measures the flow properties of blood clots. Results obtained in this way were sufficiently uniform and exhibited a measurable difference in clot firmness.

Method. Glass tubes (A′ Fig. 1) are constructed with a wide portion of 10 mm and an outlet 3 mm in internal diameter. The axial length of the tube is 11 cm, its outlet being 1.5 cm, its conus portion 2 cm and the wide part 7.5 cm long. A “00” rubber stopper is fitted into the top, the tube is inverted and filled with 5 cc of blood through the outlet. Admixture of air bubbles with the blood must be prevented. This is very important, since we found that mixing air bubbles with the blood may change the firmness of the clot significantly.