Background: Postoperative infections result from the interactions of bacteria, the surgical technique,
and host defense mechanisms. Thus, identifying single determinant factors has proved
difficult.
Magnitude of the risk: In a recent survey of 2,809 colorectal resections, transfusion was the
single most powerful risk factor for postoperative infection. In patients undergoing primary
hip or knee prosthesis insertion, the transfusion of allogeneic blood increased the risk of a
deep-seated infection by a factor of 12.
Mechanisms: Several host defense mechanisms are impaired by blood products. The initial
hypothesis incriminated the transfused white blood cells, but this paradigm has since been
challenged. The effects of free serum iron, the blood storage time, and the presence in stored
blood of bioactive substances such as inhibitors of metalloproteinase-1 may also be important.
Conclusion: It is worth pursuing efforts to emphasize autologous blood transfusion and the
reinfusion of shed blood as blood conservation strategies, as these practices reduce the risk
of infectious complications
