Fig. 2. The mean hemoglobin concentration at which physicians would transfuse erythrocytes for 55- and 75-yr-old patients in the intraoperative (IO) and postoperative periods (PO).  Open bars = 55-yr-old woman, IO;  light gray/hatched bars = 75-yr-old woman, IO;  dark gray bars = 55-yr-old woman, PO;  black bars = 75-yr-old woman, PO.