Effect of high-protein nutrition in critically ill patients: A retrospective cohort study

Early provision of a high-protein nutrition improves the prognosis of patients in intensive care units (ICUs). However, high protein intake increases blood urea nitrogen (BUN). No study has compared outcomes according to protein intake, and the clinical significance of changes in BUN (ΔBUN) in ICU patients is unclear. Here, we investigated the association of high protein intake with outcomes and BUN and assessed the clinical significance of ΔBUN.

This was a single-center retrospective cohort study. Between 1 January 2016 and 30 September 2019, 295 ICU patients received enteral nutrition for at least 3 days while undergoing mechanical ventilation. After applying the exclusion criteria of an age of <18 years, gastrointestinal disease, maintenance dialysis, renal replacement therapy after admission, kidney transplantation, and death within 7 days of commencing enteral nutrition, 206 patients remained.

Participants were divided into those receiving >1.2 g/kg/day of protein (high-protein group; n = 111) and those receiving ≤1.2 g/kg/day of protein (non-high-protein group; n = 95). The groups were balanced by propensity score matching. The primary endpoint was 28-day mortality, and the secondary endpoints were 90-day mortality, length of ICU stay, number of ventilator-free days in the first 28 days, and ΔBUN.

The high-protein group had significantly lower 28- and 90-day mortality and significantly greater ΔBUN, including after propensity score matching. ΔBUN might not be associated with outcomes.

Provision of >1.2 g/kg/day of protein may be associated with lower mortality of tube-fed and mechanically ventilated patients. Furthermore, while high protein intake may be associated with higher BUN, these changes may not be adversely associated with outcomes.