Assessment of energy consumption by indirect calorimetric method and Harris–Benedict equation in patients with severe head injury

Objective

In this prospective study, indirect calorimetry (IC) and Harris–Benedict equation were compared to find out the daily energy consumption of the patients who have severe head injury and ventilation support.

Methods

The inclusion criteria were; head injury with Glasgow Coma Scale score (GCS) ≤ 8, peripheral oxygen saturation over 95% with inspired oxygen concentration lower than 0.5. Thirty-six patients who met these criteria and were admitted to our intensive care unit (ICU) between March and October 2000 were included in the study. The Injury Severity Score (ISS), Revised Trauma Score (RTS), Acute Physiology and Chronic Health Evaluation II (APACHE) score, Glasgow Outcome score (GOS), and intensive care stay of the patients were determined. The indirect calorimetric measurements were performed by Vmax 6200 Metabolic Measurement Cart (Sensor Medics, Yorba Linda, CA, USA) in the first 48 hours following admission of the patients to the ICU. Fifty-five measurements were carried out in 36 patients and after each measurement which lasted 12 hours the mean values of resting energy expenditure (REE), O₂ consumption, and CO₂ production were noted. All of the patients were in steady-state during the measurements. Moreover, the daily nitrogen balance of all patients were determined.

Results

The basal energy expenditure calculated with Harris–Benedict equation was 1674.6 ± 317.5 kcal, and daily average resting energy expenditure (REE) measured with IC was 1881.2 ± 465.0 kcal. The energy consumption measured with IC was 12.4% higher than the value which was calculated with Harris–Benedict equation (P < 0.05). Average daily nitrogen loss was 21.6 ± 16 g.

Conclusion

The energy consumption calculated with Harris–Benedict equation had no correlation with trauma severity.

The REE measured with IC was higher in the patients who had GCS 6 or higher, RTS over 5, and ISS 25 or lower compared with the other.

There was no correlation between nitrogen loss of the patients and trauma severity.