Haemostasis is a process that involves various molecular reactions. These reactions have evolved for the basic purpose of preservation of life. The body's natural mechanisms come into play to limit blood loss after trauma. Many sequential and overlapping events occur in the body, including vasoconstriction, formation of platelet plugs, and activation of coagulation cascade. Simultaneous activation of the complement system and fibrinolysis also help to maintain the delicate balance and to restore the milieu interior. An understanding of these events and other methods of haemostasis is important in any faculty of surgery, more so in cardiac surgery.
In cardiac surgery, it is essential to understand the haemostatic process for two reasons. First, most of the patients undergoing cardiac surgery receive heparin, which is a strong inhibitor of coagulation cascade. As we intervene externally into the natural mechanism of haemostasis, we also need to know the ways to reverse the actions on the coagulation cascade. The action of heparin is reversed by protamine, which forms electrostatic complexes with the molecules of heparin. This blocks heparin's action on different steps of the cascade. Second, the incisions on the heart and the surrounding structures need be closed in such manner that they restore the blood-tight compartments. Technological advances in sutures and needle manufacturing have made major contributions in this respect. In addition, the development of new drugs and glues and topical agents like cellulose, gelatin, thrombin, and fibrinogen have also benefited surgery.
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