Hematocrit: another important factor in systemic neonatal cardiovascular adaptation

Background: Global cardiovascular adaptation of normal healthy term newborns is rarely studied from a multiorgan and hematological point of view. Aims: To evaluate comprehensive neonatal cardiovascular adaptation during the first days of life with echocardiography and renal-cerebral echo color-Doppler and to correlate it with hematocrit (Ht) changes. Study design: A prospective observational study was conducted on 35 healthy term neonates with a mean ± SD gestational age and birth weight of 39.5 ± 1.1 weeks and 3,400 ± 330 g, respectively. All infants underwent serial echocardiograms at 15 ± 4 hours (day 1) and 72 ± 4 hours (day 3) of age. At the same time, cerebral and renal Doppler parameters were acquired and Ht was sampled. Results: The weight and Ht declined by 220 g (189-251) and 8.1% (6.7-9.5), respectively. Systolic and diastolic diameters of the right ventricle and diastolic left ventricle posterior wall thickness showed a reduction, while the diastolic diameter of the left ventricle showed a small increase. The Doppler cardiac evaluation showed an increase in the mitral E/A ratio and pulmonary acceleration time, a reduction of late transmitral flow peak velocity, aortic peak systolic velocity (PSV), aortic peak systolic pressure gradient, aortic velocity-time integral, aortic mean pressure gradient and pulmonary mean acceleration. We also found a reduction of cerebral resistance parameters and an increase in PSV, end-diastolic velocity, and time-averaged velocity. Other measured parameters remained unchanged. Conclusion: Systemic cardiovascular evaluation about changes in Ht is an essential approach to study newborns, especially during the first days of life when Ht shows a significant decrease. Knowledge of the laws of physics related to the effect of Ht changes on vascular parameters is another important factor in understanding the pathophysiology of neonatal disease states. Further studies are useful to help physicians make evidence-based decisions in the management of newborns in Neonatal Intensive Care Units (NICUs).