Measurements of resting energy expenditure in surgical critically ill patients with mechanical ventilator

Abstract

Objective To compare the differences between measured resting energy expenditure calculated by the indirect calorimetry with the resting energy expenditure calculated by the Harris-Benedict formula and weight formula in the mechanically ventilated surgical critically ill patients in SICU. Methods Patients mechanically ventilated in SICU of Xuanwu Hospital, from April 2014 to April 2015 were measured resting energy expenditure by the indirect calorimetry with the resting energy expenditure calculated by the Harris-Benedict formula and weight formula in the 1st, the 3rd and the 5th day. There were twenty-nine patients enrolled, thirteen males and sixteen females, measured the resting energy expenditure 188 times.The distribution of metabolism level was studied, and the resting energy expenditure measured by three methods were calculated and evaluated by paired sample t test. Results There were 177 times(62.24%)of low metabolism level, 59 times(31.38%)of normal metabolism level, and 12 times(6.38%)of high metabolism level. Eighteen patients used these three methods to calculate the energy expenditure on 1st, 3rd and 5th day: indirect calorimetry (1 627.11±323.63) kcal, (1 614.67±308.93) kcal, (1 576.11±263.96) kcal; Weight formula (1 479.44±200.24) kcal, (1 488.40±227.72) kcal, (1434.14±216.56) kcal; Harris-Benedict formula (1 777.43±253.00) kcal, (1 730.08±265.18) kcal, (1 689.33±236.69) kcal.The results calculated from Harris-Benedict formula and the weight formula were significantly different from calculated from indirect calorimetry(P<0.05). Resting energy expenditure by Harris-Benedict formula was significantly higher than calculated from indirect calorimetry (All P<0.05). Resting energy expenditure by weight formula was significantly lower than calculated from indirect calorimetry(All P<0.05). Conclusions Although Harris-Benedict formula and weight formula is convenient in clinical use, while the results calculated by them is significant different from the results calculated by indirect calorimetry. So clinical nutrition support should rely on indirect calorimetry as far as possible. Key words: Energy metabolism; Nutritional support; Indirect calorimetry; Harris-Benedict formula; Ventilators, mechanical