Renal Resistive Index and mortality in critical patients with acute kidney injury

BackgroundThe predictive role of Doppler Renal Resistive Index (RRI) for mortality was shown in chronic kidney disease. In selected populations of intensive care unit (ICU), RRI predicts acute kidney injury (AKI) occurrence and anticipates persistent AKI. No data are available about mortality. We investigated whether RRI assay at AKI diagnosis could predict AKI mortality in a 10-bed-mixed medical-surgical and trauma ICU of a tertiary referral teaching hospital. The association between RRI and persistent AKI at discharge was investigated. MethodsOne hundred and twenty-five of 1512 patients admitted from January 2010 to March 2013 who developed AKI during ICU stay were enrolled. Kidney function was evaluated daily according to risk, injury, failure, loss and end-stage criteria. At AKI diagnosis, we measured RRI. The association between RRI at AKI diagnosis and ICU death or persistent AKI at ICU discharge was analysed by multivariable logistic regression analysis. ResultsAt AKI diagnosis, RRI was 077 (070-088) in survivors and 085 in nonsurvivors (079-094) (P=0002). RRI values were significantly associated with ICU death (OR=163-95% CI 106-249, P=0025). A RRI cut-off value of 077 was identified by receiver operating characteristic curve. Multivariate analysis selected RRI and abdominal hypertension as strongest predictors of AKI mortality. At AKI diagnosis, RRI was 078 (070-085) or 085 (073-092) (P=0026) in patients with or without persistent AKI at discharge. Multivariate analysis selected RRI at AKI diagnosis as the strongest predictor of persistent AKI. ConclusionsHigh RRI values at AKI diagnosis are strictly and independently associated with in-ICU mortality and persistent AKI at ICU discharge.