Clinical implications of the oxyhemoglobin dissociation curve in the neonatal period.

Factors responsible for determining the position of the oxyhemoglobin equilibrium curve during the neonatal period are briefly reviewed and the clinical implications of these changes are examined. Two clinical trials employing exchange transfusions as an adjunct to conventional therapy of the severe respiratory distress syndrome have both demonstrated that this procedure reduces mortality. In neither study was it possible to demonstrate that the improvement was a direct consequence of the reduction in hemoglobin's affinity for oxygen that was produced by the substitution of fetal hemoglobin by adult hemoglobin. Data on the role of the position of the oxyhemoglobin equilibrium curve in the regulation of erythropoiesis during the "anemia of prematurity" demonstrate that the ability to unload oxygen is more important than the absolute hemoglobin level in both the stimulus to erythropoietin production and the clinical manifestations of anemia. The gradual shift of the position of the oxyhemoglobin equilibrium curve which occurs during the early months of life may not be sufficient in all infants to meet the growing preterm infants' metabolic needs without evoking additional cardiac compensation.