Autotransfusion after open heart surgery: quality of shed mediastinal blood compared to banked blood.

The need to conserve a patient's own blood and avoid homologous transfusion is now well recognized. Therefore, techniques designed to reduce requirements for homologous blood transfusions have been developed. One of the methods is autotransfusion of shed mediastinal blood after open-heart surgery. The objectives of the present study were to investigate osmotic fragility and oxygen transport capacity of shed mediastinal blood compared to patient blood and stored packed red blood cells (SAGM). Shed mediastinal blood from ten consecutive patients undergoing elective cardiac surgery (coronary bypass grafting) was studied and compared to patient blood, 10 units of 3 weeks old and 10 units of 5 weeks old stored packed red blood cells (SAGM). Oxygen transport capacity was investigated by calculation of p50 for oxygen by use of the oxygen status algorithm (OSA 2.0) programme and measurement of 2,3-diphosphoglycerate (2,3-DPG) concentrations. The osmotic fragility was determined using increasing concentrations of saline. 2,3-DPG concentrations in shed mediastinal blood (5.3 mikromol/ml erythrocyte) were within the range measured in patient blood, but significantly higher than SAGM blood (P < 0.001). P50 for oxygen (3.5 kPa) in shed mediastinal blood was not significantly different compared to patient blood, but significantly higher (P < 0.01) compared with stored SAGM blood. The osmotic fragility in shed mediastinal blood was not significantly different compared to patient blood, but significantly lower (P < 0.001) than the osmotic fragility in stored SAGM blood. This suggests that red cells saved from shed mediastinal blood have better oxygen transport capacity and may have longer survival compared to stored blood.