Renal resistive index as an early predictor and discriminator of acute kidney injury in critically ill patients; A prospective observational cohort study

Abstract

BackgroundAcute kidney injury (AKI) complicates shock. Diagnosis is based on rising creatinine, a late phenomenon. Intrarenal vasoconstriction occurs earlier. Measuring flow resistance in the renal circulation, Renal Resistive Index (RRI), could become part of vital organ function assessment using Doppler ultrasound. Our aim was to determine whether RRI on ICU admission is an early predictor and discriminator of AKI developed within the first week.MethodsIn this prospective cohort of mixed ICU patients with and without shock, RRI was measured <24-h of admission. Besides routine variables, sublingual microcirculation and bioelectrical impedance were measured. AKI was defined by the Kidney Disease Improving Global Outcomes criteria. Uni- and multivariate regression and Receiver Operating Characteristics curve analyses were performed.ResultsNinety-nine patients were included, median age 67 years (IQR 59–75), APACHE III score 67 (IQR 53–89). Forty-nine patients (49%) developed AKI within the first week. AKI patients had a higher RRI on admission than those without: 0.71 (0.69–0.73) vs. 0.65 (0.63–0.68), p = 0.001. The difference was significant for AKI stage 2: RRI = 0.72 (0.65–0.80) and 3: RRI = 0.74 (0.67–0.81), but not for AKI stage 1: RRI = 0.67 (0.61–0.74). On univariate analysis, RRI significantly predicted AKI 2–3: OR 1.012 (1.006–1.019); Area Under the Curve (AUC) of RRI for AKI 2–3 was 0.72 (0.61–0.83), optimal cut-off 0.74, sensitivity 53% and specificity 87%. On multivariate analysis, RRI remained significant, independent of APACHE III and fluid balance; adjusted OR: 1.008 (1.000–1.016).ConclusionsHigh RRI on ICU admission was a significant predictor for development of AKI stage 2–3 during the first week. High RRI can be used as an early warning signal RRI, because of its high specificity. A combined score including RRI, APACHE III and fluid balance improved AKI prediction, suggesting that vasoconstriction or poor vascular compliance, severity of disease and positive fluid balance independently contribute to AKI development.Trial registrationClinicalTrials.gov NCT02558166.

Renal Resistive Index: Response to Shock and its Determinants in Critically Ill Patients

“…Previous studies found that high RRI was a predictor of AKI. Because vasopressor support showed the strongest independent relation with a high RRI and because high RRI predicts the development of AKI during the first week of ICU admission (9), our findings could indicate that too much vasopressors might unnecessarily increase renal vasoconstriction and subsequently contribute to the development of AKI. Measuring RRI using bedside ultrasound could be part of the assessment of vital organ status and function.…”

“…The study was performed at Amsterdam UMC, Vrije Universiteit Amsterdam, Department of Intensive Care Medicine, Amsterdam, the Netherlands, and is part of a larger project that additionally determines the predictive value of RRI for the development of AKI (9). The study was approved by the Ethical Board of the VUmc, which allowed a deferred consent procedure to obtain signed consent for the use of the data (VU University Medical Centre Protocol Record METC-2015.025).…”

Lack of PCSK6 Increases Flow-Mediated Outward Arterial Remodeling in Mice

“…Analysis of blood flow velocity, not dependent on circumference or wall thickness, revealed a significant increase in EDV at 3 and 5 weeks in the WT mice subjected to carotid ligation. PI and RI are non-dimensional velocity measurements used to assess organ perfusion in clinical research and to assess vascular impedance and large artery stiffness in experimental cardiovascular research [37,45]. Interestingly, a gradual decrease in PI and RI over time was observed in the Pcsk6 −/− mice, which could not be detected in the WTs.…”

The association between the renal resistive index and the myocardial performance index in the general population

“…Normal values of the RRI are reported to be between 0.60 and 0.70 4 . The diagnostic and prognostic value of the RRI has been studied in several clinical conditions such as renal transplantation, 5 renal allograft survival, 6 atherosclerotic renovascular disease, 7 acute kidney injury, 8 chronic kidney disease, 9 hypertension, 7 diabetes mellitus, 10 arterial stiffness, 11 coronary artery disease, 12,13 and heart failure 14 . Impaired renal hemodynamics, assessed by increased RRI, were found to be associated with increased cardiovascular risk 15 .…”