title: Timing of initial administration of low-molecular-weight heparin prophylaxis against deep vein thrombosis in patients following elective hip arthroplasty: a systematic review.
abstract: BACKGROUND
  Perioperative and postoperative venous thrombosis are common in patients undergoing elective hip surgery. Prophylactic regimens include subcutaneous low-molecular-weight heparin 12 hours or more before or after surgery and oral anticoagulants. Recent clinical trials suggest that low-molecular-weight heparin initiated in closer proximity to surgery is more effective than the present clinical practice. We performed a systematic review of the literature to assess the efficacy and safety of low-molecular-weight heparin administered at different times in relation to surgery vs oral anticoagulant prophylaxis.
  
  
  METHODS
  Reviewers (A.F.M. and S.M.M.) identified studies by searching MEDLINE, reviewing references from retrieved articles, scanning abstracts from conference proceedings, and contacting investigators and pharmaceutical companies. Randomized trials comparing low-molecular-weight heparin administered at different times relative to surgery with oral anticoagulants in patients undergoing elective hip arthroplasty, evaluated using contrast phlebography, were selected. Two reviewers (A.F.M. and S.M.M.) extracted data independently.
  
  
  RESULTS
  The literature review identified 4 randomized trials meeting predefined inclusion criteria. The results indicate that low-molecular-weight heparin initiated in close proximity to surgery resulted in absolute risk reductions of 11% to 13% for deep vein thrombosis, corresponding to relative risk reductions of 43% to 55% compared with oral anticoagulants. Low-molecular-weight heparin initiated 12 hours before surgery or 12 to 24 hours postoperatively was not more effective than oral anticoagulants. Low-molecular-weight heparin initiated postoperatively in close proximity to surgery at half the usual dose was not associated with a clinically or statistically significant increase in major bleeding rates (P =.16).
  
  
  CONCLUSIONS
  The timing of initiating low-molecular-weight heparin significantly influences antithrombotic effectiveness. The practice of delayed initiation of low-molecular-weight heparin prophylaxis results in suboptimal antithrombotic effectiveness without a substantive safety advantage.
authors.affiliation: Thrombosis Research Unit, University of Calgary, Alberta, Canada. Jeanne.Sheldon@crha-health.ca
authors.forename: R D
authors.initials: RD
authors.lastname: Hull
authors.forename: G F
authors.initials: GF
authors.lastname: Pineo
authors.forename: P D
authors.initials: PD
authors.lastname: Stein
authors.forename: A F
authors.initials: AF
authors.lastname: Mah
authors.forename: S M
authors.initials: SM
authors.lastname: MacIsaac
authors.forename: O E
authors.initials: OE
authors.lastname: Dahl
authors.forename: W A
authors.initials: WA
authors.lastname: Ghali
authors.forename: M S
authors.initials: MS
authors.lastname: Butcher
authors.forename: R F
authors.initials: RF
authors.lastname: Brant
authors.forename: D
authors.initials: D
authors.lastname: Bergqvist
authors.forename: K
authors.initials: K
authors.lastname: Hamulyák
authors.forename: C W
authors.initials: CW
authors.lastname: Francis
authors.forename: V J
authors.initials: VJ
authors.lastname: Marder
authors.forename: G E
authors.initials: GE
authors.lastname: Raskob
mesh_terms: D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage*; D019644:Arthroplasty, Replacement, Hip / Q000009:adverse effects*; D004334:Drug Administration Schedule; D017558:Elective Surgical Procedures / Q000009:adverse effects; D006495:Heparin, Low-Molecular-Weight / Q000008:administration & dosage*; D006801:Humans; D007279:Injections, Subcutaneous; D016017:Odds Ratio; D016032:Randomized Controlled Trials as Topic; D012107:Research Design; D012306:Risk; D020246:Venous Thrombosis / Q000209:etiology / Q000517:prevention & control*
chemical_list: D000925:Anticoagulants; D006495:Heparin, Low-Molecular-Weight