Prophylaxis against central vein thrombosis with low-dose warfarin.

Low-dose warfarin was given to patients to prevent venous thrombosis. Patients at greatest risk for having thrombi adjacent to central venous catheters were detected by the von Kaulla assay. Patients with normal von Kaulla assays had one thrombus per 1844 days at risk while those with accelerated von Kaulla assays had one thrombus per 500 days at risk. Low-dose warfarin therapy given to patients at high risk reduced the incidence of venous thrombosis from one thrombus per 251 days to one thrombus per 1617 days. Thus low doses of warfarin that do not prolong the prothrombin time appear to offer prophylaxis against venous thrombosis in patients at high risk for developing venous thrombosis adjacent to the central venous catheters.