• Giuseppe Regolisti, Umberto Maggiore, Carola Cademartiri, Loredana Belli, Tiziano Gherli, Aderville Cabassi, Santo Morabito, Giuseppe Castellano, Loreto Gesualdo, and Enrico Fiaccadori.
• Renal Failure Unit, Department of Clinical and Experimental Medicine, University of Parma, Via Gramsci, 14, 43100, Parma, Italy. giuregolisti@gmail.com.
• J. Nephrol. 2017 Apr 1; 30 (2): 243-253.

BackgroundAcute kidney injury (AKI) following major heart surgery (MHS) is associated with early decrease in renal blood flow and worsened prognosis. Doppler-derived renal resistive index (RRI), which reflects renal vascular resistance, may predict the development of AKI in patients undergoing MHS.MethodsWe studied 60 consecutive patients (mean age 69.5 years, range 30-88, 41 males) undergoing MHS. We measured RRI, both at the renal sinus and intraparenchymally, by transesophageal echo-Doppler ultrasound (TE-EDus) at anesthesia induction and at the end of surgery in all patients. Additionally, we measured RRI by external transparietal echo-Doppler ultrasound (TP-EDus) at the following time points: anesthesia induction, end of surgery, 4 and 24 h from cardiopulmonary bypass (CPB) start. We also measured serum neutrophil gelatinase associated lipocalin (NGAL) at the same time points.ResultsAKI [serum creatinine (sCr) increase ≥0.3 mg/dl vs. baseline within 72 h] developed in 23/60 (38.3 %) patients, with two requiring dialysis. Systemic hemodynamic parameters were similar in the patients who developed AKI (AKI+) and in those who did not (AKI-). Intraparenchymal RRI at end-surgery was significantly higher in AKI+ compared to AKI- patients, both at TE-EDus and TP-EDus (TE-EDus mean difference, p = 0.004; TP-EDus mean difference, p = 0.013; difference between TE-EDus and TP-EDus results, p = 0.066), although the predictive performance was limited with both methods (area under the curve [AUC] of the receiver-operator characteristics: 0.71 and 0.70 for TE-EDus and TP-EDus, respectively). Serum NGAL values were higher in AKI + than in AKI- patients (anesthesia induction, p = 0.037; end-surgery, p = 0.007; 4 h from CPB start, p = 0.093; 24 h from CPB start, p = 0.024. However, combining RRI with serum NGAL at end-surgery did not provide a clear-cut advantage in predicting AKI.ConclusionsIn patients undergoing MHS, increased echo-Doppler ultrasound-derived RRI at end-surgery is significantly associated with the risk of AKI, but has limited practical utility for identifying the patients who will develop AKI.

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