• number of red blood cell transfusions
  
• number of transfusion donors
  

• survival to discharge
  
• patent ductus arteriosus
  
• germinal matrix or intraventricular hemorrhage
  
• periventricular leukomalacia
  
• retinopathy of prematurity
  
• bronchopulmonary dysplasia
  
• duration of assisted ventilation
  
• duration of supplemental oxygen therapy
  
• number and frequency of all apnea episodes
  
• number and frequency of apnea episodes requiring tactile stimulation
  
• number and frequency of apnea episodes requiring assisted ventilation
  
• number and frequency of apnea episodes during the 24 hours before and after each transfusion
  
• time to regain birth weight
  
• time to double birth weight
  
• length of hospitalization
  
• hemoglobin
  
• hematocrit
  
• reticulocyte count
  
• oxygen saturation (pulse oximetry)
  
• cardiac output (echocardiography)
  
• blood lactic acid
  
• plasma erythropoietin
  
• serum ferritin
  

Design, Setting, and Patients. We enrolled 100 hospitalized preterm infants with birth weights 500 to 1300 g into a randomized clinical trial comparing two levels of hematocrit threshold for RBC transfusion.

Intervention. The infants were randomly assigned to either the liberal or the restrictive transfusion group. For each group, transfusions were given only when the hematocrit fell below the assigned value. In each group, the transfusion thresholds decreased with improving clinical status.

Main Outcome Measures. We recorded the number of transfusions, the number of donor exposures, and various clinical and physiological outcomes.

Results. Infants in the liberally transfused group received more RBC transfusions, mean 5.2 (SD 4.5) vs 3.3 (SD 2.9) in the restrictive transfusion group (P=0.025). However, the number of donors to whom the infants were exposed was not significantly different, mean 2.8 (SD 2.5) vs 2.2 (SD 2.0). There was no difference between the groups in the percentage of infants who avoided transfusions altogether, 12% in the liberal transfusion group vs 10% in the restrictive group. Infants in the restrictive group were more likely to have intraparenchymal brain hemorrhage or periventricular leukomalacia (P=0.012), and they had more frequent episodes of apnea (P=0.004), including both mild and severe episodes.