The plasma turnover of transfused antithrombin concentrate in patients with acquired antithrombin deficiency

Antithrombin concentrate, prepared from human plasma, has been used as replacement therapy in 35 patients with acquired antithrombin deficiency. The inhibitory activity of the concentrate, measured by chromogenic assay, correlates well with the manufacturer's quoted activity. The mean in vivo recovery of the product was 0.0124 iu mL(-1) per iu of antithrombin (AT) concentrate administered by kilogram body weight. The recovery was similar in all diagnostic groups studied and did not vary during the course of treatment. Consumption of the antithrombin concentrate was monitored by measuring the production of thrombin-antithrombin complexes and the loss of plasma antithrombin activity. The mean concentration of thrombin-antithrombin complexes was elevated (23 ng mL(-1)) at the time of admission to the intensive care unit and fell progressively over the next 4 days. The mean time for the decay of half the antithrombin activity was 23 h during the first 24 h of therapy and rose to 42.1 h after day 1. The recovery and half-life measurements are necessary ro plan an appropriate dosage regimen for the administration of this antithrombin concentrate in acquired deficiency states.