The authors present a very up-to-date review of the systemic and, in particular, the mircocirculatory effects of blood transfusions with special emphasis on the age of transfused RBCs. Maintenance of functional capillary density appears more critical for tissue oxygenation than oxygen affinity of RBCs. The need for restoring NO bioavailibility at the capillary level is particularly emphasized. In this respect, fresh RBCs are superior to stored RBCs. In general, in an adequate resuscitation from hemorrhage, restoration of microvascular perfusion and function may be as efficacious as restoring oxygen capacity.

– Konrad Messmer