Maximal parenteral glucose oxidation in hypermetabolic young children: a stable isotope study
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Published on: November 13, 2016
R L Sheridan1, Y M Yu, K Prelack
1Shriners Hospital for Children, Boston, MA 02114, USA.
Insights
Critically ill children oxidize glucose most effectively at 5 mg.kg-1.min-1. Higher glucose infusions are not oxidized and may not improve energy balance in these young patients.
Area of Science:
- Pediatric critical care medicine
- Nutritional support
- Metabolic studies
Background:
- Parenteral nutrition in critically ill children often involves high glucose infusions to meet energy demands.
- Adult data suggest high glucose loads may exceed oxidation capacity in critical illness.
- The oxidation of high glucose loads in critically ill young children remains unclear.
Purpose of the Study:
- To determine if critically ill young children can effectively oxidize high glucose loads during parenteral nutrition.
- To assess glucose oxidation efficacy at different infusion rates in pediatric burn patients.
Main Methods:
- A stable isotope study using [13C6]glucose was conducted on ten severely burned children (average age 5.2 years).
- Glucose oxidation was assessed at 5 and 8 mg.kg-1.min-1 during parenteral nutrition.
- Serum glucose levels and indirect calorimetry were used to evaluate glucose metabolism.
Main Results:
- The fraction of exogenous glucose oxidized decreased significantly from 59% to 47% as the infusion rate increased from 5 to 8 mg.kg-1.min-1.
- While total glucose oxidation increased, the efficiency of energy production decreased, with excess glucose entering nonoxidative pathways.
- Plasma glucose levels and respiratory quotients did not indicate inefficient glucose utilization.
Conclusions:
- Maximum glucose oxidation in severely burned children is achieved at approximately 5 mg.kg-1.min-1.
- Glucose infused above this level is directed to nonoxidative pathways, offering no benefit to energy balance.
- Standard clinical markers like serum glucose and respiratory quotient may not identify suboptimal glucose utilization.
Background:
During periods in which nutrition support of critically ill young children must be parenteral, glucose infusions are administered at up to 10 or more mg.kg-1.min-1 to meet predicted energy needs. However, data in adults suggest that such high glucose loads exceed the ability to oxidize glucose in the hormonal milieu that characterizes critical illness. The purpose of this study was to determine if these high glucose loads are oxidized by critically ill young children.
Methods:
Ten young children with serious burns were enrolled in a stable isotope study of glucose metabolism. These five boys and five girls were an average age of 5.2 years (range, 1 to 11 years), weight of 18.4 kg (range, 10 to 31 kg) and burn size of 51.6% of the body surface (range, 35% to 86%). During clinically required episodes of parenteral nutrition support, we used the [13C6]glucose tracer to assess the efficacy of glucose oxidation at both 5 and 8 mg.kg-1.min-1. Serum glucose was recorded and indirect calorimetry was performed.
Results:
The fraction of exogenous glucose oxidation fell from 59% +/- 5% to 47% +/- 5% (p < .05). Although there was a significantly increased level of total glucose oxidation (3.2 to 3.8 mg.kg-1.min-1), this increment (29% +/- 9%) was accompanied by a significant decrease in the efficiency of energy production, because the bulk of the additional glucose above 5 mg.kg-1.min-1 was not being oxidized. Plasma glucose concentration did not change (145 +/- 4 vs 137 +/- 4 mg/dL, p < .01) and whole-body expired gas respiratory quotients remained consistent with a mixed fuel oxidation, implying that there exists an increased rate of exogenous glucose uptake by tissues in nonoxidative pathways.
Conclusions:
Maximum glucose oxidation in severely burned children occurs at intakes approximating 5 mg.kg-1.min-1. Exogenous glucose in excess of this amount enters nonoxidative pathways and is unlikely to improve energy balance. Clinical markers such as serum glucose levels or expired respiratory quotient may not detect inefficient glucose utilization.
