Antithrombin III (AT III) functional levels are much lower in serum than in plasma; during oral anticoagulation this difference is reduced. Plasma and serum of 172 patients taking vitamin K antagonists were tested for AT III antigen and both AT III heparin cofactor and anti-Xa heparin cofactor. Crossed immunoelectrophoresis of AT III on heparin-agarose was also carried out in plasma and serum. The patients were divided into four groups: (1) international normalized ratio (INR) 9.3–4.1, n = 25; (2) INR 4.0–2.5, n = 73; (3) INR 2.4–2.0, n = 40, and (4) INR 1.9–1.5, n = 34. 66 healthy subjects were used as controls. Plasma levels of AT III antigen, AT III heparin cofactor, and anti-Xa heparin cofactor were the same in all groups. In all groups all serum AT III parameters were higher than in controls; crossed immunoelectrophoresis of AT III on heparin-agarose indicated that this finding was due to a lower formation of complexed AT III in serum. AT III heparin cofactor serum values were the same whatever the INR over a large range (9.3–1.5); the highest anti-Xa heparin cofactor serum levels were noted in the groups treated more intensely (groups 1 and 2).
In a patient with systemic lupus erythematosus, anticoagulant activity directed against factor XI was found together with thrombocytopenia. In the serum globulin fraction, antiplatelet antibodies and an activity-inhibiting platelet aggregation could also be found. A possible correlation between the inhibition of platelet aggregation and the anticoagulant activity directed against factor XI is discussed
Initially, we administered urokinase to five patients according to the following schedule: 500,000 CTA U during the first 10 min, then 250,000 CTA U/h for 12 h. Using this modality, we noted the appearance, during the first hours of treatment, of hypercoagulability. We then choose to modify the schedule by pretreatment with 7,500 U i.v. of heparin, followed promptly by 250,000 CTA U/h of urokinase (without a loading dose). This obviated the appearance of hypercoagulability without reducing the fibrinolytic effect of treatment and without producing hemorrhagic complications.
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