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Risk-adjusted strategies in the prevention of early arterial thrombosis following lower extremity arterial reconstruction: a comparison of unfractionated versus low molecular weight heparin.

AIM
In vascular surgery postoperative thrombosis prophylaxis must sufficiently prevent arterial thrombosis. This cohort study examines different therapeutic approaches of unfractionated heparin (UFH) or low molecular weight heparin (LMWH) after vascular reconstruction.


METHODS
Four hundred seventy-five patients entered the study between 2005 and 2008. Our clinical routine made a differentiation between low-risk patients (N.=375) and patients with peripheral bypass, which were grouped as high-risk (N.=148). We changed our postoperative anticoagulation management after 24 months in the low-risk and after each 16 months in the high-risk group. The anticoagulation of low-risk patients consisted of either two applications of 7.500 IU UFH subcutaneously (N.=158) or one daily application of 40 mg LMWH each up to discharge (N.=169). High-risk patients received either 25.000 IU UFH i.v. over 24 hours and 4 days (N.=48), 2-times (N.=51) or one-time weight-adjusted LMWH (N.=49) up to discharge (1 mg/kg body weight). Minor complications (bleedings) were differentiated from major early graft occlusion during the postoperative course. Further follow-up was not done for this study.


RESULTS
Low risk: under LMWH, complications could be significantly reduced (P=0.001). Under LMWH significantly fewer occlusion complications occurred (P=0.01) and operation-induced hemorrhages were less frequently observed (P=0.05), this was significant in the complete low-risk group. High-risk: the one-time weight-adjusted LMWH group similarly exhibited many occlusions, like the unfractionated group (NS). The two-time LMWH treatment was significantly superior to the one-time application with respect to occlusion followed by amputations (P=0.03). Minor complications could be minimized overall by administration of LMWH and its dose reduction (NS).


CONCLUSION
The differentiation between patients with high and low risk seems reasonable. An improvement could be achieved by differentiated LMWH application. Synthetic specific antifactor Xa substances (fondaparinux) or other medications could lead in future to other changes in the management of vascular surgery patients and should be further evaluated.