Normally, blood clots in response to vascular damage to form a local seal. The damage is repaired and the clot lysed to restore vascular patency. The original cascade or waterfall theories proposed in the 1960s by MacFarlane and Davie were enthusiastically embraced.  The mechanisms involved were artificially divided into vasoconstriction, platelet adhesion and aggregation, fibrin formation and stabilisation and fibrinolysis. These subdivisions were then measured "independently" by various bedside and laboratory tests, allowing us to pinpoint a specific deficiency in the system. However all the processes are intimately related and are initiated simultaneously, so although presented as a step wise "cascade" it must be remembered that an explosion is occurring. A firm grasp of the normal physiology and insight into the techniques used in evaluation helps in understanding why we are misled by routine testing.

The Coagulation System

Tests of the Coagulation System

Peri-operative & ICU Anticoagulation