Oxygen Transport during Erythropoietic Response to Moderate Blood Loss

Abstract The removal of 250 to 750 ml of blood over one to three weeks' time from nine normal nonsmoking males produced, one to three weeks later, slightly decreased hemoglobin concentrations (mean, 16.2 to 15.0 g per 100 ml). Oxygen pressure at 50 per cent hemoglobin saturation with oxygen (P50) increased from 27.9 to 29.8 torr (mean values) and was significantly correlated (p less than 0.005) with an average increase of erythrocyte glutamic oxalacetic transaminase activity from 4.4 to 5.4 U per gram of hemoglobin, indicating increased numbers of young erythrocytes. 2,3-diphosphoglycerate did not change (mean, 13.1 to 13.0 μmoles per gram of hemoglobin). The improved oxygen unloading afforded by the increased P50 thus seems to have more than compensated for the reduced hemoglobin concentration so that cardiac output could decrease and still maintain an unchanged normal mixed venous oxygen pressure.