[Hemorrhagic accidents of the new oral anticoagulants and coagulation assays]

New oral anticoagulants which specifically inhibit factor Xa (FXa) or thrombin (FIIa) do not require routine laboratory monitoring. However, they induce a state of hypocoagulation and increase the risk of bleeding. In some clinical situations, such as emergency surgery, hemorrhagic episodes, or recurrent stroke, coagulation monitoring may be useful. A significant number of publications have reported uncontrollable hemorrhagic complications and deaths in patients treated with these new anticoagulants. The selection of the most appropriate clotting assay is based on the drug used and the availability of the test. The new anticoagulants influence all global clot-based tests. Prothrombin time and partial thromboplastin time measured before and after treatment are considered as qualitative tests since they are not specific. Specific anti-Xa and anti-IIa assays are available and results can be expressed in nanogram per milliliter of plasma using calibrated plasmas containing well-established amounts of drug. The fact that there is no specific antidote to reverse the anticoagulant action of the new anticoagulants can impair management of hemorrhagic complications; clinical experience is still limited. Pro-hemostatic treatment with non-activated or activated prothrombin complexes (FEIBA(®)), or as a last recourse with FVIIa concentrates (NovoSeven(®)), has been used with variable results. Some suggestions for the management of patients with bleeding have been published but there is still little clinical evidence for these interventions.