Renal-Resistive Index and Acute Kidney Injury in Aortic Surgery: An Observational Pilot Study

Objective: Acute kidney injury (AKI) is a common perioperative complication in patients undergoing cardiovascular surgery, increasing mortality, morbidities, and costs. Recently, growing interest has risen in the use of the renal-resistive index (RRI) as a predictor of perioperative AKI. The aim of this study was to evaluate the role of RRI variation to identify postoperative AKI. Design: An observational, prospective, pilot study. Setting: Department of Vascular Surgery, University Hospital of Padova. Participants: The study authors included 53 consecutive patients undergoing aortic surgery from September 2018 to June 2019. Measurements and main results: Basal and daily postoperative serum creatinine and urine output were assessed. RRI was measured preoperatively and on the first postoperative day. AKI was defined using Kidney Disease Improving Global Outcome criteria. Twelve patients out of 53 developed AKI. The RRI percentage increase (%RRI) was associated with the development of AKI by univariate regression (p = 0.01). The receiver operating characteristic curve showed an overall diagnostic accuracy of 0.75 (95% confidence interval [CI], 58.2-92.6). The cutoff of 7 percentage points in the %RRI resulted in early identification of AKI onset with 90% specificity (95% CI, 76.9-97.3). The net benefit of postoperative RRI-based management was 11%. Conclusions: RRI variation could be a useful tool to investigate kidney function in patients undergoing aortic surgery. The %RRI in the perioperative time seems to detect AKI onset early and potentially could enhance renal-protective management within 24 hours after surgery.