Longitudinal evaluation of energy expenditure in preterm infants with birth weight less than 1000 g

Area of Science:

• Neonatology
• Pediatric Metabolism
• Infant Physiology

Background:

• Extremely-low-birth-weight (ELBW) infants (<1000 g) require careful monitoring of metabolic processes.
• Understanding energy expenditure (EE) is crucial for optimizing growth and development in preterm infants.

Purpose of the Study:

• To determine serial measurements of oxygen consumption (VO2), carbon dioxide production (VCO2), and energy expenditure (EE) in healthy ELBW infants.
• To analyze the relationship between energy intake, weight gain, and EE during the first 5 weeks of postnatal life.

Main Methods:

• Utilized open-circuit calorimetry to measure VO2, VCO2, and EE in 17 appropriate-for-gestational-age preterm infants (25-28 weeks gestation).
• Measurements were taken serially on days 6, 12, 18, 24, 30, and 36 of postnatal life.
• Correlations between energy intake, weight gain, and EE were assessed using statistical analysis.

Main Results:

• VO2 increased from 4.7 to 9.1 ml/kg/min, VCO2 from 4.5 to 8.3 ml/kg/min, and EE from 115 to 310 kJ/kg/d over 5 weeks.
• Energy intake consistently exceeded EE, even in the early postnatal period.
• Significant positive correlations were observed between energy intake and weight gain, EE and weight gain, and EE and energy intake (P<0.05).
• Multiple regression analysis indicated EE was more influenced by energy intake than weight gain.

Conclusions:

• Healthy ELBW infants experience a ~150% increase in EE within the first 5 weeks post-birth.
• EE in these infants is significantly related to energy intake and weight gain, independent of postnatal age.
• Findings support the importance of adequate energy provision for growth in ELBW neonates.