Energy expenditures of mechanically ventilated nonsurgical patients

Mechanically ventilated, nonsurgical, critically ill patients represent a group not rigorously studied by energy expenditure measurements for formulating nutritional support guidelines. Most strategies for predicting caloric requirements in this group are based on studies of spontaneously breathing surgical patients. It is unclear whether "severity of disease" or "stress" factors employed in this group are justifiable in medical patients with compromised pulmonary function, who may be particularly prone to the complications of overfeeding. We therefore measured the energy expenditures of 73 consecutive ventilator-supported patients with various primary diagnoses in a medical ICU. These results are compared to estimates of caloric requirements based on the Harris-Benedict equations, without modification for severity of disease or other factors. These comparisons are (kcal/day +/- SE, measured vs predicted): sepsis, 1,982 +/- 97 vs 1,534 +/- 56 (p less than 0.0001); cardiogenic shock, 1,452 +/- 119 vs 1,339 +/- 62; cardiogenic pulmonary edema, 1,427 +/- 87 vs 1,338 +/- 93; ARDS, 1,732 +/- 203 vs 1,550 +/- 125; pneumonia, 1,508 +/- 148 vs 1,259 +/- 55; and "other" 1,585 +/- 104 vs 1,419 +/- 55. These data reveal that in mechanically ventilated nonsurgical patients without sepsis, no modifications of the Harris-Benedict equations are necessary; in those with sepsis an increase of approximately 20 percent over these predictions is appropriate.