Volume 89, Issue 4, April (2003), pp. 533-537 © The Author 2003
doi:10.1079/BJN2002816

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

Jacqueline Bauer^1,*, Kathrin Maier², Gerald Hellstern¹ and Otwin Linderkamp^1
1Division of Neonatology, Department of Pediatrics, University of Heidelberg, Germany
²Department of Paediatrics, University of Freiburg, Germany

 (Received 9 May 2002–Revised 1 November 2002–Accepted 22 November 2002<)

The aim of the present study was to obtain serial values of O₂ consumption (V_O2), CO₂ production (V_CO2) and energy expenditure (EE) in healthy but extremely-low-birth-weight infants (birth weight <1000 g), during the first 5 weeks after birth. A total of seventeen spontaneously breathing and appropriate-for-gestational-age (birth weight and body length above the 10th and below the 90th percentile) preterm infants with gestational age 25–28 weeks and birth weight 590–990 g were enrolled in the study. Calorimetry was performed using an open-circuit calorimeter on days 6, 12, 18, 24, 30 and 36 of postnatal life. During the 5 weeks of observation, V_O2 increased from 4·7 (sd 0·5) to 9·1 (sd 1·0) ml/kg per min, V_CO2 from 4·5 (sd 0·4) to 8·3 (SD 0·6) ml/kg per min and EE from 115 (sd 12) to 310 (sd 71) kJ/kg per d. The energy intake was always higher than EE, even at days 6 and 12. The RER decreased from 0·99 (sd 0·09) at day 12 to 0·91 (SD 0·05) at day 30. On all study days, there were highly significant positive correlations between energy intake and weight gain, EE and weight gain, and EE and energy intake (P<0·05). Multiple regression analysis showed that on most study days EE was more affected by energy intake than by weight gain. We conclude that in healthy preterm infants with birth weight <1000 g, EE increases by about 150 % in the first 5 weeks after birth, and that the EE values are related to energy intake and weight gain independent of postnatal age.

Keywords:
Energy expenditure: Growth: Preterm: Oxygen consumption