Abstract
Sodium citrate, when administered intravenously in large doses (0.5 grams for dog or cat, 3.0 to 6.0 grams for man), produces a pronounced and progressive shortening in coagulation time of the blood which usually reaches its maximum within one hour and may persist for many hours. As a rule, the coagulation time slowly returns to normal within twenty-four hours.
This action of sodium citrate upon the coagulation of the blood in vivo is exactly opposite to what occurs in vitro. We believe that it is dependent upon some effect on the blood platelets, which are not directly destroyed by the citrate but are damaged by contact with it and are then removed from the circulation by the spleen where they are destroyed and their thromboplastic contents gradually liberated into the circulating blood. This theory is based upon the following observations:
1. In the test tube, sodium citrate does not destroy the platelets, but it effects them so that they are actually preserved and therefore more easily counted.
2. Within a few minutes after the intravenous injection of sodium citrate the blood platelets often begin to diminish in number, the maximum reduction being usually observed after ten to fifteen minutes and the number as a rule returning to normal within half to one hour. The greatest reduction in blood platelets was observed in cats, in two of which 85 per cent. and 90 per cent. of the platelets disappeared from the circulating blood within ten and fifteen minutes respectively, and the count again reached normal a half hour after the injection.
3. Increasing amounts of free thromboplastic substance (cytozyme) probably derived from platelets begin to appear in the blood stream as the coagulation time becomes shortened.
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