Use of Indirect Calorimetry to Detect Overfeeding in Critically Ill Children; Finding the Appropriate Definition

OBJECTIVES:: Overfeeding during critical illness is associated with adverse effects such as metabolic disturbances and increased risk of infection. Due to lack of sound studies with clinical endpoints, overfeeding is arbitrarily defined as the ratio caloric intake/measured resting energy expenditure (mREE) or alternatively as a comparison of measured respiratory quotient (RQ) to the predicted RQ based on the macronutrient intake (RQmacr). We aimed to compare definitions of overfeeding in critically ill mechanically ventilated children based on mREE, RQ and caloric intake to find an appropriate definition. METHODS:: Indirect calorimetry (IC) measurements were performed in 78 mechanically ventilated children, median age 6.3 months. Enteral and/or parenteral nutrition was provided according to the local guidelines. Definitions used to indicate overfeeding were the ratio caloric intake/mREE>110% and >120% and by the measured RQ>RQmacr +0.05. RESULTS:: The proportion of patients identified as overfed varied widely depending on the definition used, ranging from 22% (RQ>RQmacr+0.05), to 40% and 50% (caloric intake/mREE>120% and >110% respectively). Linear regression analysis showed that all patients would be identified as overfed with the definition RQ> RQmacr+0.05 when the ratio caloric intake/mREE exceeded 165%.Caloric intake was higher in children with an SD-score WFA <-2. CONCLUSIONS:: The proportion of mechanically ventilated patients identified as overfed ranged widely depending on the definition applied. These currently used definitions fail to take into account several relevant factors affecting metabolism during critical illness and are therefore not generally applicable to the PICU population.

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