[Heparin, low-molecular-weight heparin and their clinical use].

Numerous controlled trials have enabled the evaluation of the principal roles that standard (unfractionated) or low molecular weight heparin (LMWH) play in clinical practice. Standard heparin seems to be preferable for the treatment of venous thromboembolism, maintaining coronary patency after thrombolytic treatment for acute myocardial infarction and the treatment of unstable angina. At present, there is no convincing evidence that, in general surgery patients, LMWH has an improved benefit to risk ratio over standard heparin. LMWH is, however, preferred for patients undergoing orthopedic surgery inasmuch as it reduces the absolute risk for venous thrombosis.