How I transfuse red blood cells and platelets to infants with the anemia and thrombocytopenia of prematurity

Abstract

Many aspects of hematopoiesis are either incompletely developed in preterm infants or still functioning to serve the fetus (i.e., the intrauterine counterpart to a liveborn preterm neonate). This delayed development and/or slow adaptation to extrauterine life diminishes the capacity of the neonate to produce red blood cells (RBCs), platelets (PLTs), and neutrophils—particularly during the stress of life-threatening illnesses encountered after preterm birth such as sepsis, severe pulmonary dysfunction, necrotizing enterocolitis, and immune cytopenias. The serious medical and/or surgical problems of preterm birth can be further complicated by phlebotomy blood losses, bleeding, hemolysis, and consumptive coagulopathy. To illustrate, some preterm infants, especially those with birth weight less than 1.0 kg and respiratory distress, are given numerous RBC transfusions early in life owing to several interacting factors. Neonates delivered before 28 weeks of gestation (birth weight, <1.0 kg) are born before the bulk of iron transport has occurred from mother to fetus via the placenta and before the onset of marked erythropoietic activity of fetal marrow during the third trimester. Soon after preterm birth, severe respiratory disease can lead to repeated blood sampling for laboratory studies and, consequently, to replacement RBC transfusions. Additionally, preterm infants are unable to mount an effective erythropoietin (EPO) response to decreasing numbers of RBCs, and this factor contributes to the diminished ability to compensate for anemia—thus enhancing need for RBC transfusions. PATHOPHYSIOLOGY OF ANEMIA OF PREMATURITY During the first weeks of life, all infants experience a decline in the number of circulating RBCs. In healthy term infants, the nadir blood hemoglobin (Hb) value rarely decreases to less than 9 g per dL (mean, 11-12 g/dL) at an age of approximately 10 to 12 weeks. 1 Because this postnatal decrease in Hb level is universal and is well tolerated by term infants, it is commonly called the physiologic anemia of infancy. Among preterm infants, this decline occurs at an earlier age and is more pronounced in severity. Mean Hb concentration decreases to approximately 8 g per dL in infants of 1.0 to 1.5 kg birth weight and to 7 g per dL in infants weighing less than 1.0 kg. 2