Assessment of Resting Energy Expenditure Using Indirect Calorimetry in Surgical Patients Receiving Parenteral Nutrition

<b>Introduction:</b> The assessment of energy expenditure plays an extremely important role in the planning of nutritional treatment, especially in patients with special nutritional requirements.<b>Aim:</b> The aim of this study was to evaluate the resting energy expenditure (REE) by means of indirect calorimetry (IC) ina selected group of surgical patients receiving complete parenteral nutrition (PN) and to compare the measured REE values tothose estimated from the Harris-Benedict formula.<b>Materials and methods:</b> The study group consisted of 30 patients; the assessments as carried out on the day of initiation of PN and on the seventh day of its duration, included the measurement of REE by IC, estimation of REE using the Harris-Benedict formula, and body composition analysis by bioelectrical impedance.<b>Results:</b> The average REE in the first measurement by IC was 1488.8 451.4 kcal/day as compared to 1397.6 376 kcal/day in thesecond measurement. The mean value of REE as estimated uisng the Harris-Benedict formula was 1502.4 295.1 kcal/day (min:1028.7 kcal/day, max: 2200.76 kcal/day) on the day of initiation of PN and 1480.1 278.6 kcal/day (min: 1028.7 kcal/day, max:2046.76 kcal/day) after seven days of PN.<b>Discussion:</b> According to studies comparing REE values obtained from IC vs. those estimated from various predictive formulas in critically ill patients with special nutritional requirements, IC remains the gold standard for determining resting energy requirements.<b>Conclusions:</b> The observed difference in the measurements of resting metabolism on the day of initiation of PN and on theseventh day of PN may be suggestive of the effect of the ongoing PN on energy expenditure. REE as measured by IC was notin agreement with that estimated using the Harris-Benedict formula, which may suggest that IC is the "gold standard" for theassessment of resting metabolic rate in clinical settings.