Enhanced ex vivo proteolysis of plasma von Willebrand factor in disseminated intravascular coagulation.

Plasma levels of von Willebrand factor (vWf) are frequently elevated in patients with disseminated intravascular coagulation (DIC). To investigate the qualitative abnormalities of vWf and the possibility of its ex vivo modification in DIC, we analysed the multimeric composition of vWf in citrated plasma from 15 patients with DIC in the presence or absence of serine protease inhibitors (aprotinin and soybean trypsin inhibitor) and/or cysteine protease inhibitors (leupeptin, N-ethylmaleimide and EDTA). The proportion of large vWf multimers in plasma prepared in the presence of cysteine protease inhibitors was higher than those without such inhibitors. The addition of serine protease inhibitors during the preparation of plasma had no effect on the relative amounts of large multimers. The relative proportion of large multimers in plasma prepared without inhibitors and the difference between plasmas prepared with and without cysteine protease inhibitors correlated with plasma plasmin-alpha 2-plasmin inhibitor complex values, but not with other plasma or serum markers of DIC (platelet count, fibrinogen, FDP, D-dimer or thrombin-antithrombin III complex). We conclude that ex vivo proteolysis of plasma vWf occurs frequently in patients with DIC and cysteine protease inhibitors can protect this degradation.