Are Predictive Energy Expenditure Equations in Ventilated Surgery Patients Accurate?

Area of Science:

• Critical Care Medicine
• Nutritional Support
• Metabolic Monitoring

Background:

• Indirect calorimetry (IC) is the gold standard for determining calorie needs in critically ill patients.
• Predictive equations are often used but may misjudge resting energy expenditure (REE) in medical and mixed ICUs.
• The accuracy of these equations in surgical ICUs (SICUs) remains under-evaluated.

Purpose of the Study:

• To compare REE measured by IC with REE calculated using predictive equations and calorie goals in ventilated adult SICU patients.
• To evaluate the utility of common predictive methods for nutritional support in SICU settings.

Main Methods:

• Retrospective review of prospectively collected data from 419 mechanically ventilated adult SICU patients.
• Estimated REE using Harris-Benedict equations (HBEs) and fixed calorie goals (20, 25, 30 kcal/kg/d) with actual, adjusted, and ideal body weights.
• Measured REE using indirect calorimetry (IC).

Main Results:

• Predictive equations (HBE, 20, 25, 30 kcal/kg/d) were inaccurate for estimating REE in SICU patients, regardless of patient characteristics.
• HBE and 20 kcal/kg/d underestimated REE, while 25 and 30 kcal/kg/d overestimated it.
• Harris-Benedict equations using actual body weight (35% accuracy) and 25 kcal/kg/d adjusted body weight (34% accuracy) were the most accurate, but still imprecise.

Conclusions:

• Established predictive equations and fixed calorie goals are unreliable for determining daily caloric requirements in critically ill SICU patients.
• Indirect calorimetry (IC) measurement is crucial for accurate REE determination to guide nutritional support in SICU patients.
• Accurate caloric assessment is essential for patient recovery in the SICU.