Measurement of energy expenditure is important in order to determine basal metabolic rate and inform energy prescription provided. Indirect calorimetry is the reference standard and clinically recommended means to measure energy expenditure. This article reviews the historical development, technical, and logistic challenges of indirect calorimetry measurement, and provides case examples for practicing clinicians. Formulae to estimate energy expenditure are highly inaccurate and reinforce the role of the indirect calorimetry and the importance of understanding the strength and limitation of the method and its application.

Background Accurate measurement of energy expenditure is not widely available. Patient and clinical factors associated with energy expenditure have been poorly explored, leading to errors in estimation formulae. The objective of this study was to determine clinical factors associated with measured energy expenditure (MEE), expressed in kcal/kg/d, in critically ill children. Methods This was a retrospective study at 2 Canadian pediatric intensive care units (ICUs). Patients were mechanically ventilated children who had 1 or more MEE using indirect calorimetry. Associations between MEE and 28 clinical factors were evaluated in univariate regression and 16 factors in a multivariate regression model accounting for repeated measurements. Results Data from 239 patients (279 measurements) were analyzed. Median (Q1, Q3) MEE was 34.8 (26.8, 46.2) kcal/kg/d. MEE was significantly associated with weight, heart rate, diastolic blood pressure, ICU day of indirect calorimetry (P = 0.004), minute ventilation, vasoactive inotropic score (P = 0.004), opioids, chloral hydrate, dexmedetomidine, inhaled salbutamol (P = 0.02), and propofol dose (all P < 0.0001 unless otherwise specified) in the final multivariate regression model. Conclusions This study demonstrated association between MEE (kcal/kg/d) and factors not previously explored in pediatric critical illness. Further evaluation of these factors to confirm associations and more precisely quantify the magnitude of effect is required to support refinement of formulae to estimate energy expenditure.

Delivery of adequate nutrition after liver transplantation (LT) surgery is an important goal of postoperative care. Existing guidelines recommend early enteral nutrition after abdominal surgery and in the child who is critically ill but data on nutritional interventions after LT in children are sparse. We evaluated the impact of a standardized postoperative feeding protocol on enteral nutrition delivery in children after LT. Data from 49 children (ages 0-18 years) who received a LT prior to feeding protocol implementation were compared with data for 32 children undergoing LT after protocol implementation. The 2 groups did not differ with respect to baseline demographic data. After protocol implementation, enteral nutrition was started earlier (2 versus 3 days after transplant; P = 0.005) and advanced faster when a feeding tube was used (4 versus 8 days; P = 0.03). Protocol implementation was also associated with reduced parenteral nutrition use rates (47% versus 75%; P = 0.01). No adverse events occurred after protocol implementation. Hospital length of stay and readmission rates were not different between the 2 groups. In conclusion, implementation of a postoperative nutrition protocol in children after LT led to optimized nutrient delivery and reduced variability of care.