Recovery of [13C]-bicarbonate as respiratory 13CO2 in parenterally fed infants
Bresson, J.L.; Mariotti, A.; Narcy, P.; Ricour, C.; Sachs, C.; Rey, J.
European Journal of Clinical Nutrition 44(1): 3-9
1990
ISSN/ISBN: 0954-3007 PMID: 2162296 Document Number: 351801
A total of 10 infants on continuous total parenteral nutrition (TPN) were infused with NaH13CO3 for 6 h to assess the amount of 13C recovered as breath 13CO2. Protein intake was 2.8 g/kg daily and non-protein energy intake 107 kcal/kg daily, provided as glucose alone or as an isoenergetic glucose-lipid mixture. In the 5 infants receiving glucose as the only non-protein energy source, total CO2 production, natural 13C abundance of breath CO2 and basal 13CO2 production were higher than in the 5 infants infused with the glucose-lipid mixture. There was a good agreement, in the glucose-infused infants, between the net glucose oxidation rate measured by indirect calorimetry and the glucose oxidation rate estimated from the 13C natural abundances of breath CO2 and infused substrates. Steady-state 13C enrichment of breath CO2 was reached in all infants after 120 min of infusion. Steady-state 13C enrichment was negatively related to total CO2 production. In contrast, steady-state 13CO2 production in excess of baseline was only correlated with bicarbonate infusion rate. Mean recovery of label as respiratory 13CO2 was 98.2% of infused 13C (range: 93.1 to 104.2%), was not related to either VCO2 production or bicarbonate infusion rate and did not change with the nature of infused energy substrates. Mean apparent label retention was 2 +or- 3.2% of infused 13C, a value not significantly different from zero.