Treatment of congenital antithrombin III deficiency with concentrates.

Antithrombin III concentrates were administered to a patient with hereditary AT III deficiency undergoing orthopaedic surgery. The plasma AT III level (heparin cofactor activity) was maintained at values in excess of 100% postoperatively. A mean dose of 0.74 u/kg (range 0.64 - 0.83) of AT III resulted in a 1% increase in AT III level after concentrate infusion. The half-life of AT III (mean 66 h; range 58-76) was shorter during surgery and in the early postoperative period suggesting an increased consumption of the inhibitor. At III antigen was consistently higher than heparin cofactor activity during the first 24 h after concentrate infusions. This discrepancy was associated with the presence in the patient's plasma of an AT III fraction showing a slower mobility than the main AT III peak on two-dimensional immunoelectrophoresis in the presence of heparin. A biological assay is preferred to an immunological assay in monitoring replacement therapy with AT III concentrates.