Urinary urea, nitrogen balance and mortality in critically ill patients - A prospective cohort study

Introduction: nitrogen balance (NB) is the difference between nitrogen ingested and excreted, however its value as a prognostic marker in critically ill patients has yet to be determined. This study aimed to evaluate the association between NB, urinary parameters, and adverse outcomes among ICU patients. Methods: NB, urinary urea (UUE) and creatinine (UCE) excretion were recorded in the first week of ICU. The primary outcome was ICU mortality, and secondary outcomes were time on mechanical ventilation (MV), ICU and hospital length of stay and hospital mortality. Results: a total of 127 patients were included (58 ± 16 years, 87.4 % clinical admissions). Negative NB was observed in 77.2 % patients in the first and 47.2 % patients in the second measurement, with a protein intake of 40 (25-58) vs 86 (64-107) g/day. The ICU and hospital mortality rates were 22.0 % and 30.7 %. There was no identified cut-off point for sensibility and specificity in the ROC curves for NB and urinary parameters regarding ICU and hospital mortality. Conclusions: NB, UUE, or UCE were not associated with ICU or hospital mortality in our study. Further research is needed to evaluate the practical value of NB as a prognostic marker in ICU patients.