Antithrombin III during liver transplantation.

A III (AT-III) is a liver-synthesized plasma glycoprotein of moderate size (58 kD) that can inhibit most of the activated serine proteases involved in coagulation (eg. thrombin. activated factor X. VII. etc). The inactivation involves formation of an irreversible complex. probably filtered from the circulation of the RES. The complex formation is a time-dependent reaction requiring minutes for maximum effect. In the presence of heparin. this reaction occurs immediately. The biologic half-life of AT-Ill has not been precisely determined but is estimated at 3 to 4 days in a patient with congenital deficiency. Congenital AT·III deficiency (0.40 to 0.60 U/mL) is an uncommon disorder leading to arterial or venous thrombosis and embolism in young adults. Acquired AT-lII deficiency is much more common. In parenchymal liver cell disease. AT·III is markedly decreased .because of lack of synthesis. It is also decreased. and may reach very low values, in the presence of disseminated intravascular coagulation (DIC).