The impact of measurement of respiratory quotient by indirect calorimetry on the achievement of nitrogen balance in patients with severe traumatic brain injury.

BACKGROUND

This study evaluated the impact of IC on the optimization of nutritional support and the achievement of +NB in patients with TBI.

MATERIALS AND METHODS

27 patients (GCS ≤ 8), treated with a 5-day multimodality monitoring and goal-directed therapy protocol, received enteral nutrition on day 1 followed by IC on days 3 and 5 and assessment of NB on day 7. In the first cohort (n = 11), no adjustment in kcal was made. In the second cohort (n = 16), nutrition was targeted to an RQ of 0.83 by day 3. The first cohort was analyzed with respect to NB status; the second cohort was compared to patients with (-) and +NB of the first cohort. Data (mean ± SD) were analyzed with unpaired t test, and Chi square and Fisher exact tests.

RESULTS

4/11(36 %) patients in the first cohort had +NB. The predicted mortality by TRISS, substrate utilization, and RQ was significantly lower compared to the second cohort. The mortality predicted by the CrasH model did not differ between the two cohorts. A RQ of 0.74 was associated with the preferential use of fat and protein and -NB, whereas a RQ of 0.84 favored utilization of carbohydrates and +NB. All patients whose kcal intake was adjusted based on the RQ on day 3 reached a +NB by day 7.

CONCLUSION

An increase in kcal ≥25 % in patients with a RQ < 0.83 on day 3 improves substrate utilization, decreases protein utilization and optimizes the achievement of +NB by day 7.