[Prevention of postoperative thrombosis with low-molecular-weight heparins]

To evaluate the efficacy and safety of low molecular weight heparins (LMWHs) in thromboprophylaxis, 28 orthopaedic trials and 38 trials of patients undergoing general or gynaecological surgery were studied and subjected to a partial meta-analysis. In orthopaedic surgery the LMWHs were superior to placebo/dextran, and were at least as efficient as unfractionated heparin (UH) in the prevention of deep venous thrombosis (DVT). Compared with UH, one of the LMWH preparations significantly reduced the total incidence of DVT. The rate of non-fatal pulmonary embolism (PE) was 0.5% in the LMWH group and 1.2% among the controls receiving UH, dextran or vitamin K-antagonists. Seven orthopaedic patients died from PE (0.14%), none of whom received LMWH. In general surgery, the LMWHs were at least as efficient as UH with a trend towards a lower risk of pulmonary embolism. Compared with UH, LMWHs did not reduce the postoperative mortality rate, nor did they cause haemorrhage. LMWHs provide a safe and efficient prophylaxis by administration once daily.