Abstract
Intravenous glucose is used frequently in newborn infants to cover their energy needs. Whether this infused glucose is directly oxidised is questionable. Indirect calorimetry (IC) may overestimate the glucose oxidation rate (GOR) due to the conversion of glucose into fat. We therefore compared GOR measured by IC and 13CO2 production from U-13C-glucose. IC was performed for 6 hr, metabolic rate (MR), and GOR was calculated from the protein-free RQ and VO2. Simultaneously a primed constant infusion of U-13C-glucose was given, GOR calculated from the increase in 13CO2 excretion above baseline.A plateau was obtained after ~2 hr. 10 AGA infants were studied. BW 2.4±0.4 kg, gestational age 37±2 wks, age 9±8 days, weight 2.3±0.4 kg. Energy intake 70±14 kcal/kg/d, glucose intake 15±2.5 g/kg/d, protein intake 2.7±1.1 g/kg/d. Results: n=10, Mean±SE.
CONCLUSIONS: 1) IC shows a significantly higher glucose oxidation than U-13C methodology. 2) This difference represents glucose converted into fat with concomitant fat oxidation. 3) GOR measured by IC increased with glucose intake, but GOR calculated from U-13C-gluc showed no correlation with glucose intake. 4) GOR calculated from U-13C-gluc is 4.8 mg/kg/min, which approximates the endogenous glucose production found in previous studies.
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Sauer, P., Van Aerde, J., Smith, J. et al. GLUCOSE OXIDATION IN NEONATES, INDIRECT CALORIMETRY OR STABLE ISOTOPES?. Pediatr Res 18, 804 (1984). https://doi.org/10.1203/00006450-198408000-00073
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DOI: https://doi.org/10.1203/00006450-198408000-00073