Fibrinolysis in critically ill patients.

Impaired fibrinolysis may contribute to development of adult respiratory distress syndrome (ARDS). Pathologic increases in endogenous plasminogen activator inhibitor (PAI-1) may blunt normal fibrinolysis and unmask alternate fibrinolytic mechanisms, such as elastase-induced fibrin degradation. We measured PAI-1 and elastase-induced fibrin(ogen) degradation products in 69 critically ill patients in our medical intensive care unit (MICU) and in nine healthy volunteers. Factor VIII-related antigen protein (VIII:Ag), a reported marker of acute lung injury, and alpha-1-protease inhibitor (alpha-1-PI), an acute phase reactant, were also measured. MICU patients included 24 control patients with no known risk of ARDS, 35 patients with risk factors for ARDS including sepsis, pneumonia, aspiration, and shock, and 12 patients with ARDS including two patients from at-risk groups who developed ARDS. Plasma PAI-1 was determined by chromogenic assay, elastase-induced peptides by a new radioimmunoassay, VIII:Ag by immunoelectrophoresis, and alpha-1-PI by immunodiffusion. When compared to normal volunteers, MICU control patients had elevated PAI-1, VIII:Ag, elastase-induced peptides, and alpha-1-PI. Patients with ARDS had significantly higher PAI-1 and VIII:Ag than did MICU control patients; elastase-induced peptides and alpha-1-PI were not higher. However, at-risk patients who did not develop ARDS also had high PAI-1 or VIII:Ag. Although these data cannot refute the possible role of these compounds in the pathogenesis of ARDS, they demonstrate that PAI-1 and VIII:Ag may be elevated in many critically ill patients but may not be useful markers for the subsequent development of ARDS.