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.

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