Relationship between Energy Expenditure (EE) and Weight Gain (WG) in very low birthweight infants (VLB) auring the first weeks of life

The time course of EE was studied using an indirect calorimeter which fits into an incubator and allows around the clock measurements.In 9 VLB (1134±370g;29±3 weeks; appropriate for gest.age) V02 and VC02 were continuously measured by a mass spectrometer. From these data and urinary nitrogen excretion EE was computed. In order to assess the energetic cost of growth,EE was correlated to the rate of WG and partitionned between growth and nongrowth functions:The following characteristics of energy metabolism in the growing VLB nursed with actual technics (thermoneutrality,glucose infusion early feeding) are suggested by these results:The rate of WG is closely related to EE.The VLB is able to invest a large part of EE to cover the metabolic cost of WG.The metabolic efficiency of WG must be high as shown by the ratio WG/Intake = 0.03 g/kJ (nearly twice the value reported in healthy term babies)