VARIABILITY OF BLOOD PRESSURE INCREASES DURING FEEDING IN NEWBORNS IS RELATED TO VARIATIONS IN VOLUME OF NUTRIENT INTAKE AND NOT TO THE WORK OF FEEDING.† 846

Abstract

In previous work we have shown there are substantial increases in blood pressure in newborn infants during feeding and that increases in systolic blood pressure (SBP) are positively correlated with the volume of nutrient intake. In this current study we asked whether this correlation might be due to variability in the work of feeding and not necessarily volume of intake. Two groups of bottle feeding infants (39-40 weeks gestational age, 12-36 hours postnatal age) were fed using nipples that differed in the sucking effort required to obtain nutrient. For FAST nipples (n=15), the passive flow rate of water was 70±2ml/5min (mean±SE), whereas SLOW nipples (n=18) had flow rates of 43±2ml/5min. SBP was recorded (Dinamap) during regularly scheduled feedings. Three measurements were made immediately prior to feeding, and another three during the first three minutes of feeding. The difference in SBP between these two sets of measurements was the primary dependent variable. After the first three minutes of feeding, the volume of nutrient intake was recorded. Based on these data, the 33 infants were divided (above and below the median of 19ml) into two groups representing HIGH (n=16) and LOW (n=17) volume feeders. There was no significant effect of nipple type on volume of intake (FAST= 19.9±2.3 ml/3min vs SLOW= 17.1±2.9ml/3min). During feeding, the average increase in SBP for all 33 infants was 7.5±1.1mmHg(p<.001). A two-way ANOVA (nipple type × volume group) indicated there was a significant effect of volume group on the change in SBP(F(1,29)=4.52, p<.05) with HIGH volume feeders having larger increases in SBP than LOW volume feeders (HIGH=9.9±1.5 mmHg vs LOW=5.5±1.4mmHg). In contrast, there was no significant effect of nipple type nor an interaction between nipple type and volume group. These results support the conclusion that individual differences in the magnitude of SBP responses to feeding in infants is due more to spontaneous variation in volume of intake than to variability in feeding effort.