Janis F. Smith, MAS, MT (ASCP)Red Cross Blood Service, SBB u A merican Greater Chesapeake and Potomac Region, Baltimore, M aryland, USA S. David Rubenstein,and Children's Hospital of N ew Y ork, N ew MD u Babies Y ork, USA study evaluated the biochemical and physiologic changes in extremely premature inf ants recei-u Our ving AS-1-preserved packed red blood cells ( PRBC) stored 5 to 21 days, including increase in hemoglobin, maintenance of eug lycemia, and normal serum potassium levels, acid-base balance, and urine output. T welve inf ants ( birth weight 775 6 127 g ) with gestational age of 25 6 1 weeks received small volume replacement transfusions with 17 mL/kg PRBC preserved in an AS-1 dedicated unit. Inf ants were monitored throughout the transfusions and blood samples were obtained pre-and postransfusion f or comparison by Student's t-test. T he inf ants remained clinically stable throughout the transfusions and had an increase in hemoglobin of 2.5 g/dL. T here was no change in urine output. Serum ammonia lactate dehydrogenase ( LD H) , and glucose levels were altered as predicted. T here were also small, but clinically insigni cant, changes in serum potassium, bicarbonate , total bilirubin, and creatinine. Eug lycemia was maintained in 84% of the transfusions. We concluded that small volume transfusions with PRBC stored up to 21 days in AS-1 can be used in the very low birth weight inf ant without apparent detriment when extensive metabolic criteria are examined.Keywords additive solution 1 ( AS-1) , dedicated unit, packed red blood cells ( PRBC) , transfusion, very low birth weight ( VLBW)