title: Low-dose oral vitamin K to normalize the international normalized ratio prior to surgery in patients who require temporary interruption of warfarin.
abstract: BACKGROUND
  In patients who require warfarin interruption before surgery and have an elevated international normalized ratio (INR) before surgery, low-dose vitamin K may normalize the INR in time for surgery.
  
  
  METHODS
  In a retrospective cohort study, we assessed the efficacy of 1 mg oral vitamin K to normalize the INR for surgery and whether resistance to re-anticoagulation occurs when warfarin is restarted after surgery. We studied a cohort of patients with an INR 1.4-1.9 on the day before surgery who received 1 mg oral vitamin K (vitamin K group), and a comparator group of patients with a normal INR (< or = 1.3) on the day before surgery who did not receive vitamin K (no vitamin K group). In both patient groups, we determined the proportion of patients with a normalized INR on the day of surgery and compared the mean INR after surgery when warfarin was resumed.
  
  
  RESULTS
  Of 43 patients in the vitamin K group, the INR was normalized (< or = 1.3) in 33 patients (76.6; 95% confidence interval [CI]: 64.1-89.4), and the INR was normal or near-normal (< or = 1.4) in 39 patients (90.7; 95% CI: 82.0-99.4) on the day of surgery. The mean (standard deviation) INR in the vitamin K and no vitamin K group 4-8 days after surgery was 1.75 (0.34) and 1.59 (0.36), respectively (P = 0.56).
  
  
  CONCLUSIONS
  In patients requiring interruption of warfarin for surgery, 1 mg oral vitamin K on the day before surgery can normalize the INR by the day of surgery and may not confer resistance to warfarin re-anticoagulation after surgery.
authors: Department of Medicine, McMaster University and St. Joseph's Healthcare, Room F-544, 50 Charlton Ave. East, Hamilton, ON, Canada L8N 4A6.
authors: Karen
authors: K
authors: Woods
authors: James D
authors: JD
authors: Douketis
authors: Kala
authors: K
authors: Kathirgamanathan
authors: Qilong
authors: Q
authors: Yi
authors: Mark A
authors: MA
authors: Crowther
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000627:therapeutic use; D001777:Blood Coagulation / Q000187:drug effects; D000075202:Contraindications; D004341:Drug Evaluation; D005260:Female; D006801:Humans; D019934:International Normalized Ratio; D008297:Male; D008875:Middle Aged; D019990:Perioperative Care; D012189:Retrospective Studies; D014812:Vitamin K / Q000008:administration & dosage*; D014859:Warfarin
chemical_list: D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin