When you start a patient on Warfarin (i.e after a PE); there will be an overlap of administration of Warfarin and LMWH/ UFH for typically 5 days with a goal INR of 2-3. This is referred to as “Bridging“.
WHY? Warfarin introduces a temporary hypercoagulable stage during the first 36 hours. Protein C and Protein S (anti-coagulation factors) are vitamin K-dependent plasma proteins. Levels of these anti-coagulation factors drop faster than the pro-coagulation factors (10,9,7,2) we attempt to block with Warfarin. Therefore, bridging is used to counteract this transient pro-clotting state.
Esmon CT, Vigano-D’Angelo S, D’Angelo A, Comp PC. Anticoagulation proteins C and S. Adv Exp Med Biol. 1987;214:47-54.
Protein C / Protein S anticoagulant pathway. Anticoagulant pathway. Jeremy Parsons, M.D. (c) 2002-2016, PathologyOutlines.com, Inc.