Alterations in red cell metabolism during and following cardiac bypass surgery.

Reduced concentrations of red cell organic phosphates and increased hemoglobin--oxygen affinity have been reported during and following cardiac bypass surgery. Some have related these changes to low concentrations of ATP and 2,3-diphosphoglycerate (DPG) in stored blood while others have related them to use of the pump oxygenator. There was a 10% decrease in DPG concentration in seven dogs on cardiac bypass although the animals received no transfusions. In 16 patients who received 0 to 7 units of blood during cardiac bypass there was a decrease of 10% in the red cell DPG concentration from the preoperative value, but it did not relate to the concentration of DPG in the transfused blood bags. The magnitude of the decrease was not sufficient to impair oxygen delivery severely. The results suggest that a re-evaluation of indications for the use of fresh red cells in cardiac surgery is necessary.