[Blood transfusion : optimizing the use of a scarce and expensive resource].

Haemoglobin transfusion threshold remains debated with a high variability of practice among physicians. Several well-conducted studies revealed that a liberal transfusion policy is not only unnecessary, but can also prove harmful in certain situations. Blood transfusion is a costly act involving risks of infection, allergic and hemodynamic. Optimizing the use of this scarce and expensive resource becomes necessary. This article summarizes the different transfusion thresholds to respect in hospital clinical practice, based on the latest international recommendations, while emphasizing the importance of clinical judgment in each situation.