title: Fresh frozen plasma dosing for warfarin reversal: a practical formula.
abstract: OBJECTIVE
  To provide a practical formula for fresh frozen plasma (FFP) dosing for warfarin reversal.
  
  
  METHODS
  We reviewed data on all adult patients who received a total of 7778 units of FFP for warfarin reversal at Sentara Norfolk General Hospital (Norfolk, VA) between April 1, 2009, and March 31, 2010. Patients with advanced liver disease, consumptive or dilutional coagulopathy, and administration of activated factor VII or prothrombin complex concentrate were excluded. First, we used regression analysis on the FFP1 subset (patients whose international normalized ratio [INR] was checked before and after 1 FFP administration) and derived a simple formula: DeltaINR (PreINR - PostINR) after 1 FFP =a × PreINR +b, where PreINR and PostINR are the INR values before and after FFP administration, respectively, and a and b are constants. In the validation step, the formula obtained for the FFP1 subset was repeatedly applied to the FFP2 (patients who received 2 units of FFP back-to-back without an intervening INR check), FFP3, and FFP4 subsets.
  
  
  RESULTS
  A total of 956 patients were included. The formula DeltaINR after 1 FFP = 0.57 × PreINR - 0.72 explained 82.6% of the total variance in INR change in the FFP1 subset (n=308; P<.01). Including age, sex, weight, FFP-to-PostINR interval, or administration of vitamin K marginally improved the model. Repeated application of the FFP1 formula to the FFP2 to 4 subsets combined confirmed the accuracy of the FFP1 formula across the entire data set (n=643; R(2)=95% between predicted and actual DeltaINR; P<.01).
  
  
  CONCLUSIONS
  This formula provides a practical and accurate method for FFP dosing for warfarin reversal.
authors.affiliation: Department of Internal Medicine, Eastern Virginia Medical School, Norfolk, VA 23507, USA. rashida@evms.edu
authors.forename: Armin
authors.initials: A
authors.lastname: Rashidi
authors.forename: H Raymond
authors.initials: HR
authors.lastname: Tahhan
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000009:adverse effects*; D001778:Blood Coagulation Disorders / Q000139:chemically induced / Q000628:therapy*; D016913:Blood Component Transfusion / Q000379:methods*; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D010949:Plasma; D012044:Regression Analysis; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014859:Warfarin / Q000009:adverse effects*
chemical_list: D000925:Anticoagulants; D014859:Warfarin