Timing of initial administration of low-molecular-weight heparin prophylaxis against deep vein thrombosis in patients following elective hip arthroplasty - A systematic review

Background: Perioperative and postoperative venous thrombosis are common in patients undergoing elective hip surgery. Prophylactic regimens include su bcutaneous low-molecular-weight heparin 12 hours or more before or after su rgery and oral anticoagulants. Recent clinical trials suggest that low-mole cular-weight heparin initiated in closer proximity to surgery is more effec tive than the present clinical practice. We performed a systematic review o f the literature to assess the efficacy and safety of low-molecular-weight heparin administered at different times in relation to surgery vs oral anti coagulant prophylaxis. Methods: Reviewers (A.F.M. and S.M.M.) identified studies by searching MEDL INE, reviewing references from retrieved articles, scanning abstracts from conference proceedings, and contacting investigators and pharmaceutical com panies. Randomized trials comparing low-molecular-weight heparin administer ed at different times relative to surgery with oral anticoagulants in patie nts undergoing elective I-lip arthroplasty, evaluated using contrast phlebo graphy, were selected. Two reviewers (A.F.M. and S.M.M.) extracted data ind ependently. Results: The literature review identified 4 randomized trials meeting prede fined inclusion criteria. The results indicate that low-molecular-weight he parin initiated in close proximity to surgery resulted in absolute risk red uctions of 11% to 13% for deep vein thrombosis, corresponding to relative r isk reductions of 43% to 55% compared with oral anticoagulants. Low-molecul ar-weight heparin initiated 12 hours before surgery or 12 to 24 hours posto peratively was not more effective than oral anticoagulants. Low-molecular-w eight heparin initiated postoperatively in close proximity to surgery at ha lf the usual dose was not associated with a clinically or statistically sig nificant increase in major bleeding rates (P = .16). Conclusions: The timing of initiating low-molecular-weight heparin signific antly influences antithrombotic effectiveness. The practice of delayed init iation of low-molecular-weight heparin prophylaxis results in suboptimal an tithrombotic effectiveness without a substantive safety advantage.