Use of 13c-bicarbonate infusion for measurement of co2
production.
Spear, Michael L., Dominique Darmaun, Brenda K. Sager, W. Reed
Parsons, and Morey W. Haymond.
The Alfred I. Dupont Institute, Wilmington, Delaware; and The
Nemours Children's Clinic, Jacksonville, Florida.
APStracts 2:0020E, 1995.
To determine whether infusion of 13C-labeled bicarbonate can be used
to measure rates of carbon dioxide production (VCO2), 7 healthy
adults received 6-h primed, continuous intravenous infusions of
NaH13CO3 and L-[1-14C]leucine in the postabsorptive state while
VCO2 was measured by indirect calorimetry. Indirect calorimetry and
the use of specific activity and rate of 14CO2 expired yielded
identical values of VCO2: 8.97+/-0.82 vs 8.80+/-0.83 mmol/min (NS). The
concentration of NaH13CO3 in the infusates and the 13C enrichment in
breath CO2 were determined using gas chromatography-isotope ratio
mass spectrometry. The rate of appearance of carbon dioxide (RaCO2)
measured using the NaH13CO3 infusion rate and the steady state breath
13CO2 enrichments was 11.41+/-1.56 mmol/min, which was higher (p<0.001)
that that determined by either of the two methods. When corrected for
the recovery of labeled CO2 during the infusion of NaH13CO3 using
published values, RaCO2 was 9.24+/-0.78 mmol/min, which did not differ
from VCO2 determined using the other two methods. We conclude that
infusion of NaH13CO3 can be used to determine VCO2. This method
should be useful to study the oxidation of substrates in populations
such as ventilator-dependent neonates in whom indirect calorimetry is
laborious and inaccurate.
Received 7 November 1994; accepted in final form 31 January 1995.
APS Manuscript Number E461-4.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 25 February 1995.