**9. Prevention**

Patients with central venous catheters carry a high risk of deep arm vein thrombosis, which may exceed 60 % in certain patient groups (ICU patients, oncological and hematological patients) Van Rooden et al*.*, 2005. Therefore, approaches to prevent catheter-related thrombosis by means of pharmacological prophylaxis e.g. in cancer patients, appear attractive. However, despite an early study showing benefit of low dose warfarin in this context (Bern et al*.*, 1990), subsequent studies with warfarin and heparins could not confirm this protective effect. A recent meta-analysis did show a trend, but no significant reduction of symptomatic deep vein thrombosis with any form of thromboprophylaxis (Akl et al*.*, 2008). In accordance with these data, the current guidelines for the prevention of venous thromboembolism do not recommend routine use of thromboprophyaxis in cancer patients with indwelling central venous catheters (Geerts et al*.*, 2008).

The placement of superior vena cava filters has been reported in case reports and small case series. Although effective in preventing pulmonary embolism from thrombi in the upper extremities, these filters may cause severe complications, like cardiac tamponade and aortic perforation (Owens et al*.*, 2010) and do not protect from thrombi in the lower extremities. Therefore, the placement of these filters should be limited to special situations (Kucher, 2011).
