Uric Acid and Acute Kidney Injury in the Critically Ill

RATIONALE & OBJECTIVE: Uric acid is excreted by the kidney and accumulates in acute kidney injury (AKI). Whether higher plasma uric acid level predisposes to AKI or its complications is not known. STUDY DESIGN: Prospective observational cohort study. SETTING & PARTICIPANTS: 2 independent cohorts of critically ill patients: (1) 208 patients without AKI admitted to the intensive care unit (ICU) at Brigham & Women’s Hospital between October 2008 and December 2016; and (2) 250 participants with AKI requiring renal replacement therapy (RRT) who had not yet initiated RRT enrolled in the Acute Renal Failure Trial Network (ATN) Study. EXPOSURE: Plasma uric acid level upon ICU admission and before RRT initiation in the ICU and ATN Study cohorts, respectively. OUTCOMES: Incident AKI and 60-day mortality in the ICU and ATN Study cohorts, respectively. ANALYTICAL APPROACH: Logistic regression models were used to test the association of plasma uric acid level with incident AKI and 60-day mortality. RESULTS: In the ICU cohort, median plasma uric acid level was 4.7 (interquartile range [IQR], 3.6-6.4) mg/dL, and 40 patients (19.2%) developed AKI. Higher plasma uric acid levels associated with incident AKI, but this association was confounded by serum creatinine level and was not significant after multivariable adjustment (adjusted OR per doubling of uric acid, 1.50; 95% CI, 0.80-2.81). In the ATN Study cohort, median plasma uric acid level was 11.1 (IQR, 8.6–14.2) mg/dL, and 125 participants (50.0%) died within 60 days. There was no statistically significant association between plasma uric acid levels and 60-day mortality in either unadjusted models or after multivariable adjustment for demographic, severity-of-illness, and kidney-specific covariates (adjusted OR per doubling of uric acid, 1.15; 95% CI, 0.71-1.86). LIMITATIONS: Heterogeneity of ICU patients. CONCLUSIONS: Plasma uric acid levels upon ICU admission or before RRT initiation are not independently associated with adverse clinical outcomes in critically ill patients.