• number of patients receiving the transfusion of at least one unit of allogeneic red blood cell [ Time Frame: between the begining of surgery (day 1) and the eighth post-operative day (day 8) ]
  

• number of patients receiving the transfusion of at least one unit of allogeneic red blood cell [ Time Frame: between the administration of fondaparinux for venous thrombosis prophylaxis(8 hours after end of surgery on day 1) and the eighth post-operative day (day 8) ]
  
• post-operative major hemorrhage [ Time Frame: day 8 ]
  
• post-operative blood loss [ Time Frame: untill day 8 ]
  
• post-operative bacterial infection (combined criteria of wound infection, bronchopulmonary infection and urinary tract infection) [ Time Frame: untill six weeks ]
  
• thromboembolic events (combined criteria of venous thrombo-embolism, stroke, acute coronary syndrome and peripherial arterial thrombosis) [ Time Frame: untill six weeks ]
  

Studies in hip and knee arthroplasty (scheduled surgery) have shown that tranexamic acid decreases allogeneic red blood cell transfusion. In hip fracture surgery, an emergent procedure, transfusion is frequent. Transfusion increases adverse events such as postoperative bacterial infection and venous thrombosis. The purpose of this study is to assess the efficacy of tranexamic acid, an anti-fibrinolytic agent, in hip fracture surgery on the reduction of allogeneic red blood cell transfusion. The trial will also evaluate if the reduction in transfusion will be associated with less postoperative infection and without an increase in the thrombotic risk. Patients with an isolated hip fracture of less than 48 hours will be randomized to either tranexamic acid 15mg/kg IV at skin incision and three hours later or saline.Patients will receive fondaparinux for prophylaxis of venous thrombosis.