Antithrombin Concentrates: Clinical Indications

Abstract

Antithrombin (AT) is one of the most important inhibitors of activated clotting enzymes. It is a progressive inhibitor of factors thrombin, Xa, IXa, and XIa. Any diminu tion of activity of AT in plasma causes an increased risk of thrombosis. It is, therefore, important to detect such deficien cies. Congenital defects of AT activity cause a tendency toward venous thrombosis and pulmonary embolism, frequently begin ning between the ages of 10-15 years. In such cases a lifelong prophylaxis with oral anticoagulants is mandatory. In the case of surgery AT must be substituted to normal activity. Under this substitution an additional prophylaxis with low molecular weight heparin is also possible. In cases of pregnancy when oral anticoagulants cannot be given, substitution until delivery is necessary. Acquired AT deficiency in its most severe form is observed in consumption coagulopathy. In these cases it could be demonstrated that massive substitution of AT not only short ened the duration of this condition but was also frequently lifesaving. Antithrombin concentrates are, therefore, of consid erable importance under certain conditions. Antithrombin de ficiency is also found in the nephrotic syndrome due to massive losses of proteins. A diminished production of AT is observed in severe liver diseases. In these cases there is also a diminution of procoagulant factors and platelets resulting in a tendency toward a bleed instead of thrombosis.