Synthesis: certainties uncertainties in the prevention of deep vein thrombosis in medical patients

In medical patients there are numerous and variable risk factors for deep v ein thrombosis. Placebo-controlled clinical trials are rare. The efficacy o f standard heparin or low molecular weight heparin for the prevention of de ep vein thrombosis is clearly demonstrated for patients with recent myocard ial infarction, ischaemic stroke with hemiplegia or severe pulmonary sepsis with lung failure. Pharmacological prophylaxis is probably also efficient in patients with a severe actue disease and a certain history of deep vein thrombosis. For all other medical and especially for bedridden elderly pati ents, use of low molecular weight heparin might decrease the incidence of d eep vein thrombosis but might not modify the overall mortality. In these si tuations, placebo-controlled clinical trials are needed for best evaluation of the benefit-risk ratio.