Abstract 1113

In prior work we showed that heart rate (HR) and blood pressure (BP) of newborn infants increase during feeding. However, there is considerable variation of among individuals in these responses. In this study we tested the hypothesis that some of the variation is due to differences in sleep/wake states during testing. Sixty-four healthy, full-term, bottle-feeding infants were tested at 16-40 hrs of age. Infants were judged to be either asleep (SLP: eyes closed, regular or irregular respiration) or quiet-awake (AWK: eyes open, minimal body movements) during three periods: CRIB prior to feeding, HELD in arms of feeder, and FEEDING. HR and BP (Dinamap) data were obtained for 3 min. during each period. Twenty-seven infants remained sleeping and 25 remained awake during both the CRIB and HELD periods; 27 remained asleep and 28 awake during the HELD and FEEDING periods. BP and HR in the CRIB tended to be higher in AWK infants but this was significant only for HR (AWK 134±3 vs SLP 123±2 bpm, p<.01). Similarly, while being HELD, only HR was elevated in AWK infants (AWK 137±3 vs SLP 129±3 bpm, p<.05). In contrast to our hypothesis, there were no significant effects of state on BP responses either to being held or to being fed. However, HR changes from HELD to FED were greater in sleeping infants (AWK 7±2 vs. SLP 15±bpm, p<.01). These results suggest that differences in sleep/wake state have minimal impact on individual differences in the magnitude of BP responses to feeding, but may alter HR responses.

Supported by research grant from NICHD: R03-HD35567.