Submitted on June 20, 2007
Accepted on September 18, 2007
The recovery of labeled CO2 from acetate in severely burned children
Ricki Yvonne Fram1*, Melanie G Cree2, David L Chinkes3, David N. Herndon4, and Robert R. Wolfe5
1 Department of Surgery, University of Texas Medical Branch, Galveston, Texas, United States; Metabolism Unit, Shriners Hospital for Children, Galveston, Texas, United States; Department of Geriatrics, University of Arkansas for Medical Sciences, 4301 Markham Street, Slot #806, Little Rock, Arkansas, 72205-7199, United States
2 Preventive Medicine and Community Health, UTMB, Galveston, Texas, United States; Metabolism Unit, Shriners Hospital for Children, Little Rock, Texas, United States
3 Metabolism Unit, Shriners Hospital for Children, Galveston, Texas, United States
4 Surgery, University of Texas Medical Branch, Galveston, Texas, United States; Metabolism Unit, Shriners Hospital for Children, Galveston, Texas, United States
5 Surgery, University of Texas Medical Branch, Galveston, Texas, United States; Metabolism Unit, Shriners Hospital for Children, Galveston, Texas, United States; Geriatrics, University of Arkansas for Medical Sciences, Little Rock, Arkansas, United States
* To whom correspondence should be addressed. E-mail: rfram{at}uams.edu.
Introduction: The purpose of this study was to determine the fractional recovery rate of labeled CO2 in the breath of severely burned children. This information is needed to perform tracer studies of substrate oxidation using carbon-labeled fatty acids. Methods: Nine children, ages 4 to 14 years with massive burns participated in the study. All experiments were performed 7 days post burn after an overnight fast. A primed (60 µmol/kg), constant (2.0 µmol·kg-1·min-1) infusion of [1,2-13C] acetate was given during a 4 hour basal period and during a 4 hour hyperinsulinemic-euglycemic clamp. A priming dose (150 µmol/kg) of NaH13CO3 was given at the beginning of the study. Breath samples were collected every 10 minutes during the last 40 minutes of each period. Indirect calorimetry was performed during the last 30 minutes of each period. The isotopic enrichment of 13CO2 was determined by isotope ratio-mass spectrometry and total CO2 excretion was measured by indirect calorimetry. Results: The fractional recovery of acetate label was 0.89 ± 0.05, and 0.88 ± 0.04, during the basal state and clamp, respectively. Conclusion: The fractional recovery of labeled acetate in severely burned children is approximately three times the recovery of a non-burned adult, and similar to the value in exercising adults. The high recovery rate reflects the rapid turnover of the TCA cycle in burned children relative to the rate of exchange reactions. Minimal correction of expired CO2 data is needed in this circumstance to quantify fatty acid oxidation using 13C-labeled fatty acids.
