Coagulation defects in liver disease.

A normally functioning hemostasis system is closely related to liver function. The liver parenchymal cells produce most of the factors and inhibitors of the clotting and fibrinolytic systems, and the RES of the liver greatly aids in the clearance of activation products. Hemostasis defects thus depend on the extent of liver damage. A wide spectrum of defects is found in patients with liver cirrhosis. Owing to impaired protein synthesis, most factors and inhibitors of the clotting and the fibrinolytic systems are markedly reduced. Additionally, abnormal vitamin K-dependent factor and fibrinogen molecules have been encountered. Most patients have hyperfibrinolysis that could be DIC in nature. Thrombocytopenia and thrombocytopathy are also found. Acute or chronic hepatocellular disease may display decreased vitamin K-dependent factor levels, especially factor VII and protein C, with other factors still being normal. If patients go into hepatic failure, the abnormalities resemble those found in liver cirrhosis. Vitamin K deficiency is associated with the production of poorly functioning vitamin K-dependent factors. All other hemostasis parameters are normal. Disturbances associated with liver surgeries again depend on the underlying liver problem. Peritoneovenous shunts (LeVeen) may lead to DIC; bleeding from partially resected liver surfaces is usually a mechanical problem. Severe bleeding is encountered with orthotopic liver transplantation. It is greatly influenced by the activation of the fibrinolytic system. This occurs during the anhepatic phase and during the reperfusion phase. The hyperfibrinolysis is mediated by an intense release of t-PA. Antifibrinolytic drugs, if used cautiously, have markedly reduced bleeding and thus reduced need for blood and blood product substitution.