Most patients admitted to an ICU have multiple risk factors for thromboembolic complications, which are very often present in the guise of deep venous thrombosis (DVT) and/or pulmonary thromboembolism (PTE). Risks factors may be present before the ICU admission (advanced age, malignancy, major surgery, major trauma), or may be related to the ICU stay (such as mechanical ventilation and central venous catheters). In such settings, there are strong indications for prolonged thromboprophylaxis and/or treatment of thrombotic complications. This is achieved by a number of pharmacological and nonpharmacological provisions, each having specific advantages and shortcomings. To date, heparin and vitamin K antagonists are the two most widely used measures for both prevention and treatment of DVT and PTE. Critically ill patients are peculiar in having altered pharmacokinetic and pharmacodynamic variability. This variability can lead to unpredictable drug effects, greater toxicity, and increased potential for adverse drug effects associated with disorders of coagulation. ICU patients can receive simultaneously several different medications throughout their stay, increasing the potential for drug interactions or a synergistic/enhanced response.
