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Biological rhythmicity in preterm infants prior to discharge from neonatal intensive care
S F Glotzbach1, D M Edgar, R L Ariagno
1Department of Pediatrics, Stanford University School of Medicine, CA 94305-5119.
Insights
Preterm infants in the neonatal intensive care unit (NICU) show weak circadian rhythms. Their physiological patterns are mainly influenced by feeding and caregiving, not daily cycles.
Area of Science:
- Neonatal physiology
- Chronobiology
- Environmental influences on infant development
Background:
- Neonatal intensive care units (NICUs) disrupt natural maternal-infant rhythmic cues.
- Preterm infants lack the patterned environmental influences crucial for circadian system development.
Purpose of the Study:
- To investigate the impact of the NICU environment and nursing interventions on preterm infant circadian system development.
- To assess physiological rhythms in stable preterm infants at approximately 35 weeks postconceptional age.
Main Methods:
- Simultaneous recording of rectal temperature, abdominal skin temperature, heart rate, and activity at 2-minute intervals using a microcomputer (Vitalog).
- Data collected over three consecutive days for 17 stable preterm infants.
Main Results:
- Circadian rhythms for temperature and activity showed very low amplitude.
- Heart rate and activity levels did not significantly vary by time of day.
- Ultradian periodicities, linked to feeding and interventions, dominated physiological rhythms, with significant differences observed during caregiving periods.
Conclusions:
- Quantitative data on the preterm infant circadian system are essential.
- Understanding these rhythms can help evaluate factors improving therapeutic responses and outcomes for neonatal intensive care patients.
Objective:
The study of biological rhythms and the influence of environmental factors in the timing and synchronization of different rhythmic events have important implications for neonatal health. Preterm infants in the neonatal intensive care unit (NICU) are deprived of the patterned influences of maternal sleep, temperature, heart rate, and hormonal cycles. The impact of the NICU and nursing interventions on the development of the circadian system was studied in 17 stable preterm infants in the Intermediate Intensive Care Nursery at Stanford University for three consecutive days at about 35 weeks postconceptional age.
Outcome Measurements:
Rectal temperature, abdominal skin temperature, heart rate, and activity were simultaneously recorded at 2-minute intervals during each 3-day study by a small microcomputer (Vitalog).
Results:
Very low amplitude circadian rhythms were found for rectal and skin temperatures (maximum range 36.8 to 37.0 degrees C); population mean values for heart rate (158 bpm) and activity (3.5 counts per 2-min bin) did not differ significantly as a function of time of day. Rectal temperature, averaged in 6-hour bins over the 24-hour day as a function of both postconceptional age and postnatal age, was significantly higher during the first part of the circadian cycle. In all infants, rhythmicity in each variable was dominated by ultradian periodicities that were coincident with feedings and related interventions; moreover, several physiological variables charted during feeding differed significantly from values obtained during periods in which caregiving interventions did not occur.
Conclusion:
Quantitative data on the preterm infant circadian system may facilitate evaluation of factors that improve therapeutic responses, recovery, and outcome of neonatal intensive care patients.