Prevention of venous thromboembolism in critically ill patients

Venous thromboembolism (VTE), including deep vein thrombosis and pulmonary embolism, is one of the most common cardiovascular diseases in the world: it has been estimated that 8 out of every 100 persons over the age of 45 will develop VTE somewhere during their lifetime. About half of these events are associated with hospital stay. To prevent VTE (‘thrombosis prophylaxis’), admitted patients are often treated with low dose anticoagulant medications (‘blood thinners’), such as low-molecular-weight heparin (LMWH). Nevertheless, some critically ill patients may still develop VTE. The question is whether the efficacy of thrombosis prophylaxis can be further improved, while avoiding excessive bleeding.In this thesis, we estimate that 1 out of every 25 critically ill patients develops VTE during their hospital stay, despite receiving low dose LMWH for prophylaxis. Several factors appear associated with risk of VTE, such as having a medical history of thrombosis or receiving renal replacement therapy. Based on a comprehensive synthesis of previously published data, we conclude that intermediate dose LMWH appears to confer the best balance between benefits and harms for prevention of VTE in acutely ill hospitalised patients. Finally, we found no evidence of bioaccumulation of intermediate dose nadroparin (a commonly used LMWH-type in Europe) in critically ill patients with renal failure. This suggests that dose adjustments in these patients is unnecessary. The results of this thesis may contribute to further improving the safety and efficacy of thrombosis prophylaxis, and form a basis for the design of future intervention studies