Pathophysiology, Diagnosis, and Prevention of Neonatal Anemia

After completing this article, readers should be able to: 1. Describe the best methods of evaluating neonatal anemia. 2. Delineate the most important mechanism of anemia among critically ill term and preterm infants. 3. List the mechanisms of anemia of prematurity. 4. Describe how safe and efficacious criteria for blood transfusion are established. 5. Describe the role of clinical and laboratory postdischarge evaluation with regard to neonatal anemia. Evaluating the etiology of neonatal anemia can be a daunting task. The numerous and diverse causes of this condition can be grouped into three broad pathogenetic categories: 1) decreased erythrocyte production, 2) increased erythrocyte destruction, and 3) blood loss (Table 1⇓ ). View this table: Table 1. Pathophysiologic Classification of Neonatal Anemia The importance of obtaining a complete and accurate history and performing a physical examination for diagnosing anemia cannot be overemphasized. In particular, the infant’s family history and the mother’s obstetric history often are of critical importance in narrowing down the etiologic possibilities. The decision of whether a particular hemoglobin (Hb) value is sufficiently low to meet the criteria for neonatal anemia must be based on the infant’s birthweight, postnatal age, and the site of blood sampling. Failure to consider these factors adequately can lead to errors in diagnosis and unnecessary laboratory tests. At birth and for the first 2 to 3 months of life, healthy preterm infants have lower Hb levels than term infants. Normative data for postnatal Hb levels are readily available in standard neonatology and pediatric textbooks. Values below two standard deviations of the mean are diagnostic of anemia. It is also important to appreciate that Hb determinations performed on capillary blood samples, especially in the first days of life, are higher than those obtained from venous or arterial samples because of red blood cell (RBC) sludging in low-flow capillaries with resultant transudation of plasma. At any …