[Clinical impact of length of storage before red blood cell transfusion]

Presently, red blood cell units are stored up to 42 days in France and Canada. Length of storage of red blood cell units is not based on clinical outcomes: it is rather based on a decision made by some experts in the 1940s that red blood cell units can be stored as long as the average hemolysis is lower than 1% and the proportion of red blood cells still alive 24 hours post-transfusion is higher than 70%. Data reported recently suggest that transfusion with older red blood cell units may jeopardize the outcome of severely ill patients. In this paper, we comment the data already published on this question, and we summarize the randomized clinical trials presently on-going that were undertaken to address the relationship between length of storage of red blood cell units and outcomes of transfused patients.