Protein Requirements and Determinants of Protein Catabolic Rate in Critically Ill Patients with Acute Kidney Injury : A Post Hoc Analysis of the ENGINE Randomized Controlled Trial.

BACKGROUND & AIMS: The optimal protein requirement in critically ill patients with acute kidney injury (AKI) remains undefined. Evidence supporting individualized protein prescription guided by protein catabolic rate (PCR) is currently limited. This study aims to estimate protein requirements using PCR, identify its determinants, and evaluate the association between protein intake relative to PCR and clinical outcomes. METHODS: This study is a post hoc analysis of the open-label, randomized controlled ENGINE trial, which enrolled 80 critically ill patients with AKI. PCR was assessed in all participants using 24-hour urine urea nitrogen measurements obtained 72 hours after hospital admission. The primary outcome was the mean PCR across the study population. Secondary outcomes included identification of determinants of PCR using multiple linear regression, assessment of the association between protein intake and mortality risk, and comparison of protein intake between survivors and non-survivors at 28 days. RESULTS: Seventy-eight participants were included in the final analysis; 59% were male, with a median age of 71 years, and 80% were classified as having AKI stage 1-2. The mean PCR was 1.15 ± 0.42 g/kg/day. Body weight and blood urea nitrogen (BUN) were independently associated with PCR (p < 0.05). In multivariable Cox regression analysis, patients receiving 0.8-1.2 g/kg/day of protein intake tended to have a lower risk of 28-day mortality compared with those receiving <0.8 g/kg/day (adjusted HR 0.29, 95% CI 0.08-1.06; p = 0.062). There was no significant difference in protein intake between survivors and non-survivors at 28 days (1.10 ± 0.23 vs. 1.05 ± 0.32 g/kg/day, p = 0.40). CONCLUSIONS: This post hoc analysis supports the feasibility of individualized protein prescription guided by PCR in critically ill patients with AKI and identifies a mean protein requirement of 1.15 g/kg/day.