Dangerous potentials in medicamentous prophylaxis of thrombosis - Low molecular-weight heparins versus standard heparins.

Introduction: At present, low molecular-weight heparins are recommended for efficient prophylaxis of thrombembolic complications (TEC), especially in the high-risk areas of orthopedics and trauma surgery. In addition to improved efficacy, a markedly reduced risk of side-effects should also be of great advantage, particularly in terms of heparin-induced thrombocytopenia (HIT) type II, a medicative side-effect which can be associated with severe to life-threatening complications. Methods: In a prospective study, the incidence of heparin-induced thrombocytopenia HIT type II and the incidence of symptomatic TEC in high-risk orthopedic patients was investigated when the low molecular-weight heparin, enoxaparin, was applied. An analogous study using standard heparin (UFH) served as the comparison group. When the thrombocyte count dropped by 50% compared to the initial value, or when thrombembolic complications with clinical symptoms arose, the serum was examined in the heparin-induced platelet activation test (HIPA test). Phlebography was used to verify symptomatic TEC. Results: 325 patients who had undergone surgery for total hip or knee arthroplasty or for the revision of hip and knee total endoprostheses took part in the study. 3 patients (0.92%) developed clinically symptomatic complications. No HIT type II was observed in the study population. The comparison group (UFH) consisted of 307 patients who had undergone analogous surgery. 13 patients (4.2%) developed clinically symptomatic TEC. In 10 patients (3.3%), these were associated with HIT type II The difference in the thrombosis rate and incidence of HIT type II between the two groups is highly significant. Conclusion: For the prophylaxis of thrombembolic complications - especially in the high-risk areas of orthopedics and trauma surgery - unfractioned standard heparin (UFH) is insufficiently effective and associated with a high risk of side-effects, particularly of HIT type II. Low molecular-weight heparins must thus be considered the preferred medication in thrombembolism prophylaxis.