title: Comparing Usual Care With a Warfarin Initiation Protocol After Mechanical Heart Valve Replacement.
abstract: BACKGROUND
  The immediate postoperative warfarin sensitivity for patients receiving heart valve prostheses is increased. Established warfarin initiation protocols may lack clinical applicability, resulting in dosing based on clinical judgment.
  
  
  OBJECTIVE
  To compare current practice for warfarin initiation with a known warfarin initiation protocol, with doses proportionally reduced to account for the increased postoperative sensitivity.
  
  
  METHODS
  We compared the Mechanical Heart Valve Warfarin Initiation Protocol (Protocol group) with current practice (clinical judgment-Empirical group) for patients receiving mechanical heart valves in an observational before-and-after format. End points were the time to achieve a stable therapeutic international normalized ratio (INR), doses held in the first 6 days, and overanticoagulation in the first 6 days.
  
  
  RESULTS
  The Protocol group (n = 37) achieved a stable INR more rapidly than the Empirical group (n = 77; median times 5.1 and 8.7 days, respectively; P = 0.002). Multivariable analysis indicated that the Protocol group (hazard ratio [HR] = 2.22; P = 0.005) and men (HR = 1.76; P = 0.043) more rapidly achieved a stable therapeutic INR. Age, serum albumin, amiodarone, presence of severe heart failure, and surgery type had no impact. Protocol patients had fewer doses held (1.1% vs 10.1%, P < 0.001) and no difference in overanticoagulation (2.7% vs 9.1%, P = 0.27).
  
  
  CONCLUSIONS
  The Mechanical Heart Valve Warfarin Initiation Protocol provided a reliable approach to initiating warfarin in patients receiving mechanical aortic or mitral valves.
authors: 1 Flinders Medical Centre, Bedford Park, South Australia, Australia.|2 Flinders University, Bedford Park, South Australia, Australia.
authors: Gregory
authors: G
authors: Roberts
authors: 3 University of South Australia, Adelaide, South Australia, Australia.
authors: Rasha
authors: R
authors: Razooqi
authors: 2 Flinders University, Bedford Park, South Australia, Australia.
authors: Stephen
authors: S
authors: Quinn
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage* / Q000627:therapeutic use*; D001777:Blood Coagulation / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006350:Heart Valve Prosthesis; D019918:Heart Valve Prosthesis Implantation / Q000379:methods*; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D014859:Warfarin / Q000008:administration & dosage* / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: anticoagulation; cardiovascular drugs; clinical pharmacy; dosing; surgery; warfarin