Energy expenditure in the critically ill performing early physical therapy

Resting energy expenditure (REE) determination is of high relevance to avoid both overfeeding and underfeeding. We conducted an observational study to determine the impact of early exercise on energy requirements to adjust caloric intake accordingly in critically ill patients.

This was a prospective observational study conducted in an intensive care unit in 49 hemodynamically stable critically ill patients and 15 healthy volunteers. Indirect calorimetry (IC) was performed for 15 min at baseline during resting conditions, and then continuously recorded during 30 min of cycling at 0, 3, or 6 watts (W), followed by a 15-min resting period. REE determined by IC was compared with predictive formulas and correlated with several biomarkers. The energy cost of early exercise was compared between critically ill patients and healthy volunteers.

In patients, REE determined by IC was higher than predicted by Harris-Benedict (29 ± 31 %, p < 0.001) and Fleisch equations (23 ± 31 %, p < 0.001) but lower than predicted by the Faisy-Fagon equation for ventilated patients (16 ± 19 %, p < 0.05). Differences between Harris-Benedict predictions and IC determination were positively correlated with C-reactive protein (CRP) in patients with sepsis (r = 0.51, p = 0.003). During a similar exercise, VO2 increase in patients was higher when compared with healthy volunteers at 3 W, close to significant at 6 W, and not present in the passive group.

The critically ill have increased REE according to inflammation defined by CRP. Increased energy requirement for physical activity was only present for active exercise and seems to differ from that in the healthy population. For the exercise duration and intensity tested, nutritional adjustment is not indicated.