The role of low-molecular-weight heparins in the prevention of venous thrombosis in surgery with special reference to enoxaparin.

Prophylaxis with low-dose heparin has contributed significantly to the reduction in thromboembolic complications in surgery. Without prophylaxis, the rate of deep-vein thrombosis is about 30% in patients undergoing general surgery, rising up to 70% in orthopedic and trauma surgery. According to Collins et al. [N Engl J Med 1988; 318: 1162-1172] and Clagett and Reisch [Ann Surg 1988; 208: 227-240] heparin prevented at least 60% of deep-vein thromboses. Meanwhile, various heparin fragments have become available for clinical use and the question arises whether these low-molecular-weight heparins are equal or even superior to unfractionated heparin in preventing thromboembolic complications. Because of the pharmacological heterogeneity of low-molecular-weight heparins and variations in administered doses, this question can only be partially answered by meta-analysis. However, in summary it can be said that despite the difficulties of and concerns about general assessments, single daily injections of low-molecular-weight heparin are at least as efficacious as multiple daily doses of unfractionated heparin. In particular, enoxaparin 40 mg once a day and enoxaparin 30 mg twice a day seem to be superior to unfractionated heparin in high-risk patients, and adverse drug reactions occur less frequently when this prophylaxis is used.