Factors that influence mesenteric artery blood flow velocity in newborn preterm infants

Objectives: To identify demographic and clinical variables that relate to the postnatal increase in intestinal blood flow velocity in preterm infants. Study design: Fasting or preprandial peak systolic velocity (P SV) and time-averaged mean velocity (TAMV) in the superior mesenteric artery were measured once each day for the first 5 days of life. We investigated the relationship between blood flow velocity and the following variables: birth weight, gestational age, feeding volumes, number of days to reach full feeding volumes, type of feeding given, continuous positive airway pressure (CPAP) administration and hyperalimentation (HAL) administration. Results: Twenty-five infants with a mean birth weight of 1740g and mean gestational age of 31.8 weeks were studied. There were significant increases in PSV (P<0.001) and TAMV (P=0.005) from postnatal day 1 to 5. The postnatal increase in TAMV and PSV was attenuated in infants administered CPAP or HAL for ≥3 days; the results remained significant after controlling for birth weight and gestational age. There was a significant correlation (P<0.02) between volume of enteral feedings given on 2 of 5 days for TAMV, and on 1 of 5 days for PSV. Conclusions: These data support previous findings of significant increases in intestinal blood flow in preterm infants during the first week of life, and of inconsistent effects of enteral feeding volumes on fasting or preprandial intestinal blood flow. The reasons for, and the clinical implications of, attenuated increases in postnatal intestinal blood flow in infants on CPAP or HAL require further investigation.