Haematocrit and red blood cell transport in preterm infants: an observational study

Aims-To test whether cardiac output acts as a compensatory response to chan ges in haematocrit. Methods-A cohort of 38 preterm infants (27-31 weeks' gestation) was studied with repeated Doppler measurements of left ventricular output during the I st month of life. Red blood cell transport was calculated when the duct was closed. Results-Multiple regression analysis showed that left ventricular output co rrelated negatively with haematocrit when the duct was closed (n = 84) and when it was open (n = 59). The influence of an increase of 10% in haematocr it absolute value on mean (SD) left ventricular output was estimated at -55 (11) mg/kg/min. Mean (SD) red blood cell transport was 132 (30) ml/kg/min with a mean (SD) intra-individual variability of 20% (8.8%). Red blood cell transport was increased more frequently by left ventricular output than by haematocrit. Haematocrit and left ventricular output but not red blood cel l transport were dependent on postnatal age. Conclusion-These results suggest that in preterm infants cardiac output ada ptation is effective in attenuating the effects of red blood cell mass vari ations on systemic oxygen carrying capacity.