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Energy expenditure in critically ill children
G Briassoulis1, S Venkataraman, A E Thompson
1Department of Anesthesiology/CCM, University of Pittsburgh, PA, USA.
Insights
Measured energy expenditure (MEE) in critically ill children is often lower than predicted values. Nutritional support should be guided by MEE to prevent over- or underfeeding and improve outcomes.
Area of Science:
- Pediatric critical care medicine
- Clinical nutrition
- Metabolic research
Background:
- Accurate assessment of energy expenditure is crucial for critically ill children.
- Existing formulas for predicting energy needs may not be reliable in this population.
- Protein-energy malnutrition is a concern in critically ill pediatric patients.
Purpose of the Study:
- To measure energy expenditure in critically ill children using indirect calorimetry.
- To compare measured energy expenditure (MEE) with predicted values from standard formulas.
- To correlate MEE with nutritional status and clinical severity.
Main Methods:
- Prospective clinical study in a pediatric intensive care unit.
- Indirect calorimetry to measure oxygen consumption and carbon dioxide production.
- Calculation of measured energy expenditure (MEE) using the modified Weir formula.
- Assessment of nutritional status (e.g., chronic and acute protein-energy malnutrition) and illness severity (e.g., Pediatric Risk of Mortality Score).
Main Results:
- MEE was significantly lower than predicted energy expenditure and recommended daily allowances in most patients.
- MEE was lower in patients with multiple organ system failure.
- Protein intake, nutritional markers (midarm muscle/fat area), vasoactive agent use, and sedation correlated with MEE.
- Depletion of protein stores was associated with higher incidence of multiple organ system failure, and fat stores depletion with increased mortality.
Conclusions:
- Standard formulas and stress-related corrections overestimate energy expenditure in critically ill children.
- Measured energy expenditure (MEE) is often close to or lower than resting energy expenditure (PBMR).
- Lower MEE is associated with increased morbidity, highlighting the need for individualized nutritional support based on MEE to avoid over- or underfeeding.
Objectives:
To measure energy expenditure in critically ill children and compare it with the energy expenditure predicted by recommended formulas, and relate the measured energy expenditure to nutritional and clinical indices.
Design:
A prospective, clinical study.
Setting:
Tertiary care pediatric intensive care unit in a university children's hospital.
Patients:
A total of 37 patients with critical illness who were mechanically ventilated for > or =24 hrs were studied.
Interventions:
None.
Measurements And Main Results:
Chronic protein-energy malnutrition (CPEM) and acute protein-energy malnutrition were defined by the Waterlow's stages and fat and protein stores were classified as defined by Frisancho, Ryan, and Martinez. Severity of illness was assessed by the Pediatric Risk of Mortality Score, the Therapeutic Intervention Scoring System, and indices of organ failure. Oxygen consumption, carbon dioxide production, and the respiratory quotient were measured by indirect calorimetry, and energy expenditure (MEE) was calculated using the modified Weir formula. Resting energy expenditure (PBMR), predicted energy expenditure, and caloric intake were calculated using recommended formulas. A total of 77 measurements were made in 37 children. MEE was significantly lower than PBMR as estimated by all equations except the Talbot equations. MEE was significantly lower than predicted energy expenditure and the recommended daily allowances. On the first day, the MEE/PBMR ratio was <0.9 in 56.8%, 0.9-1.1 in 21.6%, and >1.1 in 21.6% of patients. MEE did not differ significantly among disease groups or between medical and surgical patients. There was no difference in MEE with or without neuromuscular blockade. MEE was lower in the presence of multiple organ system failure (MOSF) (1019 + 166 kcal/m2 without MOSF vs. 862 + 241 with MOSF; p = .025). A total of 21% had CPEM and 8.1% had acute protein-energy malnutrition. Multivariate stepwise regression analysis showed that the protein intake, midarm muscle area, midarm fat area, the use of vasoactive agents, and sedation correlated with MEE (p < .05). With CPEM, MEE was correlated to the severity of illness (p < .05). Patients at risk for protein stores depletion (midarm muscle areas 1 and 2) had a higher incidence of MOSF compared with nutritionally normal children (p < .05), whereas patients with fat stores depletion (midarm fat area 2) had a higher probability of death (50% vs. 6%, respectively).
Conclusions:
Recommended daily allowances and energy expenditure predicted by using a stress-related correction to the resting energy expenditure grossly overestimate MEE. MEE is close to PBMR and in many patients, it is lower than PBMR. MEE that is lower than PBMR is associated with a higher morbidity. Nutritional repletion should thus be based on MEE to avoid the problems of over- or underfeeding.
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