SummaryTreatment monitoring based on a laboratory parameter increases the efficacy and safety of standard heparin therapy, but it is not known if this also applies to low-molecular-weight heparin (LMWH) therapy of acute deep vein thrombosis (DVT). In a prospective randomized trial involving 122 consecutive patients, group A (58 patients) received a weight adjusted dose of Fragmin (100 IU/kg) subcutaneously twice a day throughout the treatment period (10 days ± 1), while in group B (64 patients) the dosage was based on the results of an anti factor Xa (anti Xa) amidolytic assay to obtain a target concentration from 0.5 to 1 IU/ml. AntiXa and antithrombin activities were also measured retrospectively on frozen plasma from all patients. The two regimens were comparable in terms of hemorrhagic complications (4 in group A and 3 in group B). Bilateral ascending phlebography was performed before inclusion and at the end of LMWH treatment. Treatment efficacy, based on Marder’s score, did not differ between the two groups (p = 0.3). Dosage adjustment to between 0.5 to 1IU anti-Xa/ml does not therefore appear to improve the efficacy or safety of LMWH tieatment. However, correlations between the change in Marder’s score and both anti-Xa (p <0.001) and antithrombin activity (p <0.001) were observed, suggesting a relationship between the degree of FXa or thrombin inhibition and antithrombotic activity.

SummaryEight patients with heparin associated thrombocytopenia (HAT) were treated by a low molecular weight heparin derivative (LMW). Biological and clinical improvement occurred in all patients. This efficiency confirms the antithrombotic activity of LMW and allows its use in patients with HAT.

SummaryWe compared in six patients successively treated with an unfractionated heparin (UFH) and a low molecular weight heparin (LMWH) the variations in plasma anti-Xa activity, measured in a chromogenic assay, during a 36 h constant infusion. The values varied in a wider range during UHF infusion, but remained in the therapeutic range except once in one patient. No circadian rhythm could be demonstrated in our six patients. LMWH infusion yielded very constant anti-Xa circulating activities. In both cases, there were no significant modifications of three proteins with high heparin affinity (antithrombin III, heparin cofactor II, histidine-rich glycoprotein).Our results suggest that the circadian rhythm of the biological activities previously observed in patients treated with constant heparin infusion using clotting method is due to other factors than heparin itself.

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