Protein C deficiency and portal thrombosis in liver transplantation in children.

Changes in plasma protein C and antithrombin concentrations after liver transplantation were monitored in fourteen children and a control group of fourteen adults. In the children, there was a persistent deficiency in the plasma concentration of protein C and a less pronounced deficiency in antithrombin during the early postoperative period, causing a hypercoaguable state. A concomitant rise in plasminogen activator inhibitor further increased the risk of thrombosis by inhibiting fibrinolysis. These changes coincided with the peak incidence of portal vessel thrombosis (4-10 days). Replacement of plasma antithrombin, together with heparin, did not prevent portal thrombosis in two of the children. It is concluded that successful prevention will require protein C replacement together with antithrombin supplements up to, but not exceeding, normal plasma activity.