title: Brief communication: Preoperative anticoagulant activity after bridging low-molecular-weight heparin for temporary interruption of warfarin.
abstract: BACKGROUND
  Preoperative low-molecular-weight heparin (LMWH) is often used when warfarin therapy is interrupted for surgery.
  
  
  OBJECTIVE
  To determine the preoperative anticoagulant activity of LMWH following a standardized "bridging" regimen.
  
  
  METHODS
  Prospective cohort study.
  
  
  METHODS
  Single university hospital.
  
  
  METHODS
  Consecutive patients who had warfarin therapy interrupted before an invasive procedure.
  
  
  METHODS
  Enoxaparin, 1 mg/kg of body weight, twice daily. The last dose was administered the evening before surgery.
  
  
  METHODS
  Blood anti-factor Xa heparin levels measured shortly before surgery.
  
  
  RESULTS
  Preoperative anti-Xa heparin levels were obtained in 80 patients at an average of 14 hours after the last dose of enoxaparin was administered. The average anti-Xa heparin level was 0.6 U/mL. The anti-Xa heparin level, measured shortly before surgery, was 0.5 U/mL or greater in 54 (68%) patients and 1.0 U/mL or greater in 13 (16%) patients. A shorter interval since the last dose (P < 0.001) and a higher body mass index (P = 0.001) were associated with higher preoperative anti-Xa heparin levels.
  
  
  CONCLUSIONS
  The small sample size limits accurate estimates of the frequency of the clinical outcomes. A single regimen of LMWH was evaluated.
  
  
  CONCLUSIONS
  Anti-Xa heparin levels often remain high at the time of surgery if a last dose of a twice-daily regimen of LMWH is given the evening before surgery.
authors.affiliation: McMaster University and Hamilton Health Sciences Foundation, Hamilton, Ontario, Canada. odonnm@mcmaster.ca
authors.forename: Martin J
authors.initials: MJ
authors.lastname: O'Donnell
authors.forename: Clive
authors.initials: C
authors.lastname: Kearon
authors.forename: Judy
authors.initials: J
authors.lastname: Johnson
authors.forename: Marlene
authors.initials: M
authors.lastname: Robinson
authors.forename: Michelle
authors.initials: M
authors.lastname: Zondag
authors.forename: Irene
authors.initials: I
authors.lastname: Turpie
authors.forename: Alexander G
authors.initials: AG
authors.lastname: Turpie
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics*; D004334:Drug Administration Schedule; D017984:Enoxaparin / Q000008:administration & dosage* / Q000009:adverse effects / Q000493:pharmacokinetics*; D015951:Factor Xa / Q000378:metabolism; D005260:Female; D006470:Hemorrhage / Q000139:chemically induced; D006801:Humans; D008297:Male; D008875:Middle Aged; D011300:Preoperative Care / Q000379:methods*; D012307:Risk Factors; D018401:Sample Size; D013923:Thromboembolism / Q000139:chemically induced; D014859:Warfarin / Q000627:therapeutic use; D028761:Withholding Treatment
chemical_list: D000925:Anticoagulants; D017984:Enoxaparin; D014859:Warfarin; D015951:Factor Xa