Measured Energy Expenditure Using Indirect Calorimetry in Post-Intensive Care Unit Hospitalized Survivors: A Comparison with Predictive Equations

Actual energy needs after a stay in intensive care units (ICUs) are unknown. The aims of this observational study were to measure the energy expenditure (mEE) of ICU survivors during their post-ICU hospitalization period, and to compare this to the estimations of predictive equations (eEE). Survivors of an ICU stay >= 7 days were enrolled in the general ward during the first 7 days after ICU discharge. EE was measured using the Q-NRG calorimeter in canopy mode. This measure was compared to the estimated EE using the Harris-Benedict (HB) equation multiplied by a 1.3 stress factor, the Penn-State (PS) equation or the 30 kcal weight-based (WB) equation. A total of 55 adults were included (67.3% male, age 60 (52-67) y, body mass index 26.1 (22.2-29.7) kg/m(2)). Indirect calorimetry was performed 4 (3-6) d after an ICU stay of 12 (7-16) d. The mEE was 1682 (1328-1975) kcal/d, corresponding to 22.9 (19.1-24.2) kcal/kg/day. The eEE values derived using HB and WB equations were significantly higher than mEE: 3048 (1805-3332) and 2220 (1890-2640) kcal/d, respectively (both p < 0.001). There was no significant difference between mEE and eEE using the PS equation: 1589 (1443-1809) kcal/d (p = 0.145). The PS equation tended to underestimate mEE with a bias of -61.88 kcal and a wide 95% limit of agreement (-717.8 to 594 kcal). Using the PS equation, agreement within 15% of the mEE was found in 32/55 (58.2%) of the patients. In the present cohort of patients who survived a prolonged ICU stay, mEE was around 22-23 kcal/kg/day. In this post-ICU hospitalization context, none of the tested equations were accurate in predicting the EE measured by indirect calorimetry.

Automated summary

The study found that the actual energy expenditure (mEE) of ICU survivors during their post-ICU hospitalization period was around 22-23 kcal/kg/day, while the estimations from predictive equations (HB and WB) were significantly higher than the measured values. The PS equation was more accurate in estimating mEE.