Nothing!
According to a study published in the American Journal of Respiratory and Critical Care Medicine, patients who received a blood transfusion from within four days of the donation showed responded no differently than patients who received a blood transfusion within the shelf life of 26 days.
A study was done with 100 patients to test the theory that the longer a donation is stored the higher the risk of transfusion-related pulmonary complications. Fifty patients received fresh blood donations and the other fifty received stored blood donations.
The results showed there was no difference in short-term pulmonary, immunologic or coagulation status.
For more information about this study, check out Medpage Today.