Early postnatal changes in superior mesenteric artery blood flow velocity in healthy term infants.

OBJECTIVES: After birth, the newborn intestinal circulation undergoes physiological changes. The purpose of this work was to characterize the changes in mesenteric blood flow velocity occuring during the first three days of life in healthy term infants. METHODS: 30 healthy term newborns were studied repeatedly at the age of 2, 24 and 70 hours. Blood flow velocity in superior mesenteric artery (SMA) was measured by Doppler ultrasound, peak systolic velocity (PSV), end-diastolic velocity (EDV) and time-averaged mean velocity (TAV) were recorded at each time point. Resistance index (RI) and pulsatility index (PI) were calculated. RESULTS: SMA EDV increased from 2 h [-5.2+/-6.8 cm/s (mean +/- SD)] to 24 h (12.9+/-3.8 cm/s, p<0.001) with further insignificant increase to 70 h (14.9+/-4.7 cm/s). At 2 h of age the mean EDV was negative in 23 of 30 cases (76.7%). PSV did not change between 2 h (58.0+/-21.8 cm/s) and 24 h (58.5+/-15.0 cm/s) but it increased to 70 h (79.6+/-17.7 cm/s). TAV showed a significant increase with time. RI decreased from 2 h (1.09+/-0.11) to 24 h (0.78+/-0.06, p<0.001) with further insignificant increase to 70 h (0.81+/-0.06). CONCLUSIONS: The blood flow velocity in SMA increases during the early neonatal period in term infants. The most remarkable changes occur within the first 24 hours of life. At 2 h of age a reversed blood flow is present in majority of infants.

Assessment of renal circulation in small for gestational age and appropriate for gestational age term newborns: a prospective study.

PURPOSE: To compare selected parameters of renal circulation between small for gestational age (SGA) and appropriate for gestational age (AGA) newborns. METHODS: Fifty-two SGA and 100 AGA term newborns were examined. The size of the kidneys were measured, and renal blood flow in the central and intraparenchymal renal arteries were assessed via Doppler sonography. Peak systolic velocity (PSV), end diastolic velocity (EDV), mean blood flow velocity (V mean), resistance index (RI), and pulsatility index (PI) were determined and compared between the groups. RESULTS: No statistically significant differences in the velocity parameters were found between SGA and AGA infants in central renal arteries. Slightly higher RIs and PIs were seen in AGA newborns (RI, 0.76 +/- 0.13 versus 0.78 +/- 0.06 [p < 0.05]; PI, 1.65 +/- 0.54 versus 1.84 +/- 0.46 [p < 0.05]). There were statistically significant differences between the groups in all measured parameters in intraparenchymal arteries (RI, 0.57 +/- 0.11 versus 0.63 +/- 0.05 [p < 0.001]; PI, 0.89 +/- 0.26 versus 1.09 +/- 0.16 [p < 0.001]) except PSV (7.11 +/- 1.55 versus 7.14 +/- 0.81 cm/s [p > 0.05]). CONCLUSION: Based on our findings, we suggest that renal circulation is not negatively influenced by intrauterine growth restriction in SGA neonates compared with AGA newborns.