[Potentials risks in drug prevention of thrombosis--low-molecular-weight heparin versus standard heparin]

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.

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.

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.

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.