SHORT-TERM EFFECTS OF BLOOD-TRANSFUSION ON BLOOD-VOLUME AND RESTING PERIPHERAL-BLOOD FLOW IN PRETERM INFANTS

The effects of blood transfusion on cardiac output and blood pressure are variable, but resting peripheral blood flow (RPBF) may be a sensit ive indicator of changes in blood volume. The purpose of this investig ation was to study the effects of red cell transfusion on blood volume (Evans blue), blood pressure, RPBF in the leg (strain-gauge plethysmo graphy) and blood viscosity (cone-plate viscometer) in preterm infants during the first week after birth. Fourteen infants with mean +/- SD birth weight of 1658 +/- 429 g, gestational age 33 +/- 3 weeks and pos tnatal age 64 +/- 40 h received 18 +/- 4 ml/kg of packed red cells (re d cells 11 +/- 2 ml/kg, plasma 7 +/- 1 ml/kg) because their hematocrit was less than 0.45 1/1. Mean blood volume before transfusion was 88 /- 15 ml/kg. The increase in blood volume (9 +/- 4 ml/kg) measured 4 t o 6 h after transfusion was smaller than the transfused volume (18 +/- 4 ml/kg), due to a shift of plasma to the extravascular space. The pl asma shift increased with increasing pretransfusion blood volume (r = 0.70; p = 0.007). Red cell transfusion caused an increase in RPBF by 2 5% (p < 0.01), whereas systolic blood pressure (BP) increased by only 12%. Peripheral resistence (R=BP/RPBF) decreased by 9% (p < 0.01). Blo od viscosity (eta) increased by 21% (p < 0.001) and vascular hindrance (R/eta) decreased by 24% (p < 0.001), indicating vasodilatation of li mb arteries. The increase in RPBF and the decrease in hindrance were p articularly pronounced in infants with high pretransfusion blood volum e. We conclude that the increase in blood volume after transfusion is not proportional to the transfused volume and that RPBF increases more than systolic blood pressure with increasing blood volume. The increa se in RPBF can be explained by vasodilatation of limb arteries and by increased blood pressure.