Background. Pulmonary blood flow and resistance may change after packed red cell transfusion since marked effects on systemic circulation have been observed in preterm infants. Patients and methods. Right ventricular output (RV-CO), right ventricular preejection periods (RPEP), right time peak velocity (RTPV), right ventricular ejection times (RVET), ratio of RTPV/RVET(c) corrected for heart rate, and blood viscosity were studied in thirty preterm infants (mean ± SD; gestational age of 29± 5 wks, birth weight 1135 ± 390 g, postnatal age of 48 ± 21 days, and an actual weight of 1935 ± 432 g) before and after transfusion of 10 ml/kg pure packed red cells-by means of a pulsed Doppler device. Statistic. Two tailed paired t -test; P-value<0.05. Table

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Conclusion. The RPEP/RVETc ratio and the RTPV/RVET(c) ratio did not change in spite of increased blood viscosity suggesting unchanged pulmonary resistance. Our results indicate that transfusion of packed red cells improves pulmonary red cell transport (RV-CO x HKt; i.e. oxygen transport) in spite of decreased RV-CO, but does not affect pulmonary resistance in preterm neonates.