Impact of autotransfusion after coronary artery bypass grafting on oxygen transport

Background: Autotransfusion of shed mediastinal blood after coronary artery bypass grafting (CABG) has been shown to reduce the requirement for allogeneic blood. We have previously demonstrated in non-randomized studies that the oxygen capacity of shed mediastinal blood is similar to the patient's circulating blood and better than stored allogeneic blood. Therefore, we wanted to examine the influence of autotransfusion of shed mediastinal blood on oxygen transport capacity in patients undergoing CABG.
Methods: A prospective, randomized, controlled study involving 120 patients having elective, uncomplicated CABG was performed. The autotransfusion group received transfusion of shed mediastinal blood for 18 h. Both groups received allogeneic red cells if their hemoglobin concentration decreased below 5 mmol/L. Red blood cell 2, 3-diphosphoglycerate (2, 3-DPG) was measured preoperatively and at intervals up to the hospital discharged. Hemodynamic measurements as well as blood gas and hemoglobin measurements from samples of arterial and mixed venous blood were used for calculation of oxygen transport capacity.
Results: During the autotransfusion period only 2 patients (4%) in the autotransfusion group required allogeneic blood compared to 11 patients (20%) in the control group. The 2, 3-DPG levels in the autotransfusion group were unchanged before and after autotransfusion (4.4 vs. 4.3 umol/ml erythrocyte). In the control group, 2, 3-DPG levels decreased from 4.3 to 3.9 umol/ ml erythrocyte during the same period. There were no differences in the other measured parameters for oxygen transport capacity between the groups.
Conclusion: Autotransfusion of shed mediastinal blood conserves the 2, 3-DPG level of the red blood cells, while transfusion of stored blood leads to a decrease in 2, 3-DPG levels. Autotransfusion had no effect on hemodynamic parameters, oxygen delivery or oxygen extraction.