MYOCARDIAL, ERYTHROPOIETIC, AND METABOLIC ADAPTATIONS TO ANEMIA OF PREMATURITY

We determined the effects of anemia of prematurity on myocardial, meta bolic, and erythropoietic functions. Twelve anemic (hemoglobin range, 65 to 78 gm/L) infants without symptoms (gestational age, (mean +/- SD ) 28 +/- 2 weeks; birth weight, 1178 +/- 326 gm) were studied at a pos tconceptional age of 35 +/- 1.6 weeks. All measurements were done befo re and 36 to 48 hours after a transfusion of packed erythrocytes. Card iac output, heart rate, and myocardial function were assessed. Oxygen consumption, carbon dioxide production, resting energy expenditure, ar terial oxygen pressure for 50% hemoglobin saturation, and the concentr ations of erythropoietin and 2,3-diphosphoglycerate were also determin ed. After transfusion, increased hemoglobin level (75 +/- 4 to 150 +/- 16 gm/L) and decreased oxyhemoglobin affinity (20.8 +/- 1.7 to 23.6 /- 2.1 gm/L; p < 0.05) caused a decrease in plasma erythropoietin conc entration (from 21.1 +/- 6.2 to 5.8 +/- 1.5 mU/ml; p < 0.01). There wa s a decrease in heart rate (from 155 +/- 10 beats/min to 146 +/- 7 bea ts/min) and cardiac output (from 281 +/- 73 ml/kg per minute to 199 +/ - 62 ml/kg per minute; p < 0.05). Myocardial function indexes, weight gain, and metabolic demands were normal before and after transfusion. These results suggest that oxygenation is adequately maintained in sym ptom-free infants with anemia of prematurity.