Reduction of homologous blood requirements by blood-pooling at the onset of car to pulmonary bypass

Abstract

This study was done to investigate whether an intraoperative autologous blood donation (pooling) at the onset of cardiopulmonary bypass can reduce homologous blood requirements during and after operations for myocardial revascularization. Ninety patients were assigned equally to two groups. In group C, serving as the control group, cardiopulmonary bypass was done with a membrane lung primed with 1500 ml of Ringer's solution. The cardiopulmonary bypass flow ranged between 2.4 L/min per square meter in normothermia and 1.5 L/min per square meter in moderate hypothermia of 30 degrees to 32 degrees C. In group P the same devices were used as in group C; however, at the onset of cardiopulmonary bypass 500 to 1000 ml of heparinized blood was "pooled" in a bag and substituted by the same volume of Ringer's solution. The lower hemodilution limit was set to a hematocrit value of 20%. The pooled blood was retransfused after the aorta was decannulated. The main parameter of interest was the total volume of red cell concentrates and fresh frozen plasma required during the operation and the subsequent stay in the hospital. The results were that group C received on average 792 +/- 639 ml and group P 337 ml +/- 382 ml of red cell concentrates. Very small amounts of fresh frozen plasma were used on average: group C, 56 ml; group P, 0 ml. These differences were highly significant (p < 0.001). Remarkably, 44% of patients in group P did not require any homologous blood products compared with 16% in group C. In conclusion, modern oxygenators, which provide sufficient oxygen transport capacity, make it feasible to decrease the hematocrit to 20% by "pooling" blood at the beginning of cardiopulmonary bypass and replacing it with saline solution. This procedure led to a highly significant saving of homologous blood.