A Method for Distinguishing Between “Activation” and Addition Effects when Mixing Coagulants

Abstract

Mills 1 reported results obtained on mixing serum and lung extract; in general there was noted an increase followed by a decrease in the coagulative power of the mixture. He particularly emphasized the tremendous increase in coagulative power that occurs immediately after mixing. He used the decrease in the clotting time of a recalcified citrate plasma as an index of coagulative power.

Burns, Scharles and Aitken 2 reported a study on a series of kidney extracts from different animals incubated with various sera. Using the decrease in clotting time of heparinized plasma as an index of coagulative power, they secured results somewhat similar to those obtained by Mills with lung extract.

Considerable interest attaches to the interpretation of this phenomenon in terms of coagulation theory. In order accurately to determine whether activation occurs and the extent of the activation where it does occur, it is necessary to use a method which will measure activation at its height (according to available data this is immediately after mixing). And since serum as well as tissue extract has coagulative power, the method used should permit distinguishing between addition and “activation” effects.

The following method is found to meet the above requirements. Decrease in the clotting time of recalcified citrate rabbit plasma is used as the index of coagulative power. Coagulation time is determined in 10 mm. tubes kept in a water bath at 30°C. The materials are added in the following order. Plasma, 2 drops; 1% CaCl₂, optimum amount; coagulant; 0.9% NaCl to make 10 drops. The strength of the coagulants is now adjusted, by dilution of the stronger with saline, until 2 drops of either decrease the clotting time of the recalcified citrate plasma to the same extent.