Fluid balance, biomarkers of renal function and mortality in critically ill patients withAKI diagnosed before, or within 24h of intensive care unit admission: a prospective study.

Abstract

To evaluate fluid balance, biomarkers of renal function and its relation to mortality in patients with acute kidney injury (AKI)diagnosed before, or within 24h of intensive care unit admission. A prospective cohort study considered773 critically ill patients observedover six years. Pre-intensive care unit-onset AKI was defined as AKI diagnosed before, or within 24h of intensive care unit admission. Body weight-adjusted fluid balance and fluid balance-adjusted biomarkers of renal function were measured daily for the first three days of intensive care unit admission. Primary outcome was mortality in theintensive care unit. Prevalence of pre-intensive care unit-onset AKI was 55.1%, of which 55.6% of cases were hospital-acquired and 44.4% were community-acquired. Fluid balance was higher in AKI patients than in non-AKI patients (p < 0.001) and had a negative correlation with urine output (p < 0.01). Positive fluid balance and biomarkers of renal function were independently related to mortality. Multivariate analysis identified the followingAKI-related variables associated with increased mortality: (1) In AKI patients: type 1 cardiorenal syndrome (OR 2.00), intra-abdominal hypertension (OR 1.71), AKI stage 3 (OR 2.15) and increase in AKI stage (OR 4.99); 2) In patients with community-acquiredAKI: type 1 cardiorenal syndrome (OR 5.16), AKI stage 2 (OR 2.72), AKI stage 3 (OR 4.95) and renal replacement therapy (OR 3.05); and 3) In patients with hospital-acquiredAKI: intra-abdominal hypertension (OR 2.31) and increase in AKI stage (OR 4.51). In patients with pre-intensive care unit-onset AKI, positive fluid balance is associated with worse renal outcomes. Positive fluid balance and decline in biomarkers of renal function are related to increased mortality, thus in this subpopulation of critically ill patients, positive fluid balance is not recommended and renal function must be closely monitored.