Objective: Nutritional monitoring is still controversial in critically ill patients. Although a high protein intake appears to
be beneficial, protein nutritional adequacy can be optimized by appropriate monitoring. Nitrogen balance (NB) may be
an important tool in this context. This study aimed to identify factors related to higher or lower NB values in critically ill
patients, assess the impact of NB on outcomes (mortality), and evaluate whether the temporal evolution of NB impacts
these outcomes.
Material and Methods: This prospective cohort evaluated patients with intensive care unit (ICU) stay ≥24 h in two hospitals.
NB was evaluated on ICU days 1, 5, and 10.
Results: We evaluated 234 patients (63.7% men, 52.7 years old; 17.9% medical, 15.8% trauma, and 60.7% elective postoperative).
Factors correlated with a more negative NB were mechanical ventilation, trauma or medical etiology, and chronic
obstructive pulmonary disease, or cancer as comorbidities. There was no correlation between NB values and mortality.
Among patients who were more severely ill [acute physiology and chronic health evaluation (APACHE) score >10] and had
more negative 1st NB (greater catabolism), those who died revealed less negative NB over the course of days, whereas
those who survived maintained stable NB (more negative).
Conclusion: In a heterogeneous ICU population, NB values did not correlate with mortality. However, in the more severely
ill patients (lower APACHE) and in those who were more catabolic (more negative initial NB), evolution to less negative NB
(lower catabolism) on days 5 and 10 correlated with higher mortality.