Patients with fulminant hepatic failure have severe circulatory disturbances which may be due to fibrin and cellular plugs in micro-vessels which are a consequence of intravascular coagulation and which can lead to multiorgan failure. Since antithrombin III supplementation has been shown to be beneficial in animal models of septic shock with disseminated intravascular coagulation, a controlled study was performed to investigate the effect of antithrombin III supplementation in fulminant hepatic failure. Twenty-five patients in grade III or IV coma were selected on the basis of evidence of sepsis, intravascular coagulation and a high risk of developing multiorgan failure. Thirteen patients received 3000 units of antithrombin III (Kybernin P; Behringwerke), followed by a further 1000 units every 6 h. Antithrombin III activity increased from 0.26 +/- 0.04 SE U/ml to 0.82 +/- 0.07 U/ml at 3 h post infusion (normal range 0.80-1.20 U/ml) and remained greater than 0.80 U/ml throughout the study without any apparent increase in the frequency of bleeding. However, survival was not improved and markers of intravascular coagulation remained similar between the two groups. Thus, although the antithrombin III deficiency in fulminant hepatic failure can be corrected by supplementation with antithrombin III concentrate, its use in the prevention of intravascular coagulation and to avoid microvessel plugging needs to be studied at an earlier stage in the disease.