Abstract
The hemoglobin (Hgb) in a premature infant usually falls to 8-10 gm/dl at 6 weeks of age. Infants 4-6 weeks old are often transfused above this range in the NICU if requiring supplemental oxygen or ventilator support. We measured cardiac output (CO) and calculated systemic oxygen transport (SOT) [CO × O2 content of arterial blood] in infants to evaluate if maintaining these higher Hgbs actually improved oxygen transport to tissues. CO was measured by pulsed-Doppler echocardiography in the ascending aorta before and within 2 hours following transfusion with 10cc/kg packed cells. 2-3 DPG, % fetal Hgb, and arterial blood gases were measured before and after transfusion. Infants less than 4 weeks of age (n=5) were compared to infants 4-8 weeks old (n=5). In the younger infants the mean Hgb went from 10.3 to 13.3 gm/dl (within normal range for their age) and CO was 186 (±52) cc/kg/min before transfusion and 187 (±35) cc/kg/min after transfusion. SOT rose by 19% in these infants. In the older infants, Hbg went from 11 to 13.3 (above the normal range for age) and CO fell from 204 (±57) cc/kg/min to 141 (±52) cc/kg/min (p<.01), and SOT fell by 19%. We conclude that maintaining Hgb in neonates above the normal range for their age may not improve oxygen transport to tissues, but may actually cause a decrease in oxygen delivery.
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