Summary
Hematologic studies of an infant who was admitted for shock and was treated with a
large volume of pooled aged plasma disclosed striking prolongation of a variety of
coagulation tests, including the prothrombin time, partial thromboplastin time, and
thrombin time. The aged plasma produced a marked anticoagulant effect on normal plasma
in vitro with the results suggesting inhibition of the thrombin-fibrinogen reaction. Similar
results were obtained with 24 different lots of aged plasma from 5 different sources.
The inhibitory factor of aged plasma behaved as a competitive inhibitor of the conversion
of fibrinogen to fibrin, as compared with heparin which is a noncompetitive inhibitor.
Infusion of aged plasma into rabbits produced a defect similar to that found in the
patient. Biochemical and immunologic studies revealed that the plasma was devoid of
fibrinogen but contained large amounts of a fibrinogen degradation product. Treatment
of the plasmas with protamine or with rabbit IgG anti-human fibrinogen removed the
anticoagulant activity. Development of anticoagulant activity during plasma aging
did not appear to be related to fibrinolysis, as it was unaffected by addition of
a fibrinolytic inhibitor. Because of the anticoagulant activity of aged plasma, it
must be used with caution in patients having underlying hemostatic disorders. Coagulation
screening tests in patients who have received recent infusions of aged plasma may
lead to misinterpretation unless specific coagulation factor assays are performed.
