In a recently completed three-year multicenter trial, 90 individuals with adult
acute respiratory distress syndrome (ARDS) were randomly allocated to conventional
therapy with or without long-term
extracorporeal membrane oxygenation (ECMO). This study conclusively demonstrated that ARDS is associated with frequent major
bleeding and thrombotic episodes and that the
bleeding correlates best with the degree of
thrombocytopenia and is enhanced by the machine. Neither
heparin's therapeutic efficacy nor its ability to increase
bleeding could be proven. ARDS is associated with a complex coagulation disturbance. Besides
thrombocytopenia, there were lowered circulating levels of factors VII and XII which may be related to changes in the pulmonary endothelium. ECMO was associated with relative
leukopenia and a marked shift to immature circulating leukocytes. Further studies are needed to better define the clinical importance of
thrombosis and
bleeding in the lung, the role for
heparin in treatment, and the meaning of reductions in
coagulation factors in defining the course, prognosis and response to
therapy of patients with ARDS.