The Oxygen-Affinity of Hemoglobin: Influence of Blood Replacement and Hemodilution after Cardiac Surgery
Red cell 2,3-diphosphoglycerate (2,3-DPG) is an important factor affecting the affinity between oxygen and hemoglobin (2). The infusion of stored blood during and after operations employing cardiopulmonary bypass produces a decrease in the 2,3-DPG concentration in erythrocytes (4,5). Low concentrations cause an increase of the oxygen affinity for hemoglobin resulting in a left shifted oxygen dissociation curve. From a high arterial oxygen tension to a given tissue pO2, less oxygen is unloaded from the blood to the tissue. In addition, blood loss and fluid replacement during and after surgery cause an acute decrease of hemoglobin, lowering the arterial oxygen content. Oxygen transport to the tissues may be compensated by an increase in cardiac output or oxygen extraction. Reduced hemoglobin concentration has been found to decrease affinity of oxygen for hemoglobin by adaptive rise in red cell 2,3-DPG (6,9). The purpose of this study was to examine the possible compensation of the progressing hemodilution by a decreasing oxygen affinity to hemoglobin in order to maintain a sufficient oxygen supply to the tissue.
KeywordsOxygen Transport Open Heart Surgery Oxygen Affinity Oxygen Release Oxygen Breathing
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