[Coagulation and the general surgeon. Its physiology and laboratory tests]

Mechanisms of coagulation and appropriate laboratory tests necessary for general surgical procedures are outlined. Physiologic features discussed include: platelet coagulation (with a brief analysis of the release and the role of prostaglandins); the equilibrium between plasma coagulation and lysis, each dependent on activators and inhibitors (a total of 4 enzymatic systems); and finally the role of the liver, lungs, and reticuloendothelial system. However, the two types of coagulation are narrowly intricated. Vessel endothelium prevents or assists platelet adhesion, coagulation, and lysis. An important feature is that total blood coagulates more rapidly than plasma. Physiopathological features described are activation of platelets or their inhibition by anti-aggregants, and induction of coagulation by endothelial lesions or eruption of an autologous or heterologous protease, as well as a brief outline of consumption coagulopathy and disseminated intravascular coagulation, and the concept of hypercoagulability. With respect to laboratory tests it is suggested that an overall picture of coagulation of total blood and not of plasma should be obtained before individual examinations for certain coagulation or lysis elements. Minimum data necessary preoperatively are the coagulation and bleeding times, completed by questioning the patient, the costs of these procedures being insignificant. If laboratory tests are necessary, these should involve a thromboelastogram of total blood, sometimes combined with a test of ADP-induced platelet aggregation. Certain plasma tests can provide complementary confirmatory data. These remarks are obviously applicable to general and digestive surgery only, and not to research investigations or the study of rare phenomena.