The assay of overall haemostasis potential used to monitor the low molecular mass (weight) heparin, dalteparin, treatment in pregnant women with previous thromboembolism.

The present study aimed to assess whether the determination of overall haemostasis potential (OHP) in plasma is powerful enough to monitor the prophylactic effect of low molecular mass heparin (dalteparin, Fragmin) in patients with increased risk of thromboembolitic events. In five pregnant women who had a history of deep venous thrombosis, OHPs were kinetically investigated in gestation weeks 32-35 twice during 24 h (before injection and after 1, 2, 4, 6, 8, 10, 12, 14, 16 and 24 h). Levels of anti-activated factor X (anti-FXa), reflecting dalteparin activity, as well as prothrombin fragments 1 + 2 (F1 + 2) and soluble fibrin, were also measured. In converse relation to changes of anti-FXa, OHPs decreased reaching the lowest level between 2 and 8 h after the injection, and then rose again, returning to the levels around those before the administration. There were no significant variations in concentrations of F1 + 2 and soluble fibrin during the observation course. These findings indicate that the OHP assay can monitor the alteration of haemostatic balance under the dalteparin influence while anti-FXa only shows the activity of the drug present in plasma. Additionally, analyses of thrombin generation markers are not useful to screen immediate changes in the haemostatic system after dalteparin injection.