Arch Intern Med
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Review Meta Analysis
Preoperative or postoperative start of prophylaxis for venous thromboembolism with low-molecular-weight heparin in elective hip surgery?
Prophylaxis of venous thromboembolism with low-molecular-weight heparins in patients undergoing major orthopedic surgery is currently initiated according to at least 3 different regimens. In Europe, traditionally, prophylaxis is started 12 hours before surgery, whereas in North America it is initiated 12 to 48 hours postoperatively. The third regimen (perioperative) begins prophylaxis either earlier than 12 hours before or 12 hours after surgery. Unfortunately, the optimal regimen is uncertain because direct comparisons among these regimens with sufficiently large sample sizes are not available. ⋯ We find no convincing evidence that starting prophylaxis preoperatively is associated with a lower incidence of venous thromboembolism than starting postoperatively. Perioperative regimens may lower the risk of postoperative thrombosis, but if so, this positive effect is offset by an increase in postoperative major bleeding.