What are the clinical determinants of early energy expenditure in critically injured adults?

The clinical determinants of energy expenditure in critically injured adults require definition. Among adult blunt trauma victims who required mechanical ventilation, the resting energy expenditure was calculated with the Harris-Benedict equation (HBEE) and the early (< or = 5 days postinjury) energy expenditure was measured by indirect calorimetry (MEE) (n = 115). The MEE was 2052 +/- 531 kcal/day and MEE/HBEE ("stress factor") was 1.24 +/- 0.2. The MEE was correlated with HBEE, age, height, weight, sex, temperature, and paralytic agents (p < 0.01). However, MEE did not correlate with ISS, admission GCS score, admission base deficit, initial systolic blood pressure, or the number of units of packed red blood cells transfused in the first 24 hours after injury (p = NS). Temperature and paralysis correlated with MEE/HBEE (p < 0.01). A regression model of MEE was developed with the clinical variables HBEE, temperature, and the presence or absence of paralytic agents (r2 = 0.62; p < 0.001): MEE (kcal/d) = 1.4(HBEE) + 71.4(temperature) + 274(paralytics; + = 1, - = 2) - 3485. In mechanically ventilated trauma victims, both the early energy expenditure and the stress factor are determined by host factors but are independent of the severity of the anatomic and physiologic insult. The degree of hypermetabolism observed in this population was less than previously reported.