title: Doppler-based renal resistive index can assess progression of acute kidney injury in patients undergoing cardiac surgery.
abstract: OBJECTIVE
  The objective of this study was to test whether assessment of renal resistive index measured after cardiac surgery (RRI(T0)) can diagnose persistent acute kidney injury (AKI). The predictive value was evaluated using a gray-zone approach.
  
  
  METHODS
  A prospective observational study.
  
  
  METHODS
  A teaching university hospital.
  
  
  METHODS
  Eighty-two patients following cardiac surgery with cardiopulmonary bypass.
  
  
  METHODS
  Measurements of hemodynamic parameters and RRI were obtained before surgery, on admission to the intensive care unit, 6 hours after admission, and on the first postoperative day. AKI was defined according to the renal risk, injury, failure, loss of kidney function, end-stage of kidney disease (RIFLE) classification during the first postoperative week. Persistent AKI was defined as AKI lasting >3 days.
  
  
  RESULTS
  Out of the 82 patients, 15 (18%) developed persistent AKI, and 6 (7%) developed transient AKI. The median value and time-course of RRI were significantly different between patients with transient AKI and persistent AKI. Doppler-based RRI(T0) predicted persistent AKI with an area under the receiver-operating characteristic curve of 0.93 (95% confidence interval: 0.85-0.98, p<0.0001). The optimal cut-off of RRI was 0.73 (95% confidence interval: 0.73-0.75). The gray-zone approach identified a range of RRI values between 0.72 and 0.75 in 14% of patients.
  
  
  CONCLUSIONS
  Doppler-based RRI can be helpful for noninvasive assessment of renal function recovery after cardiac surgery by using RRI(T0) to predict persistent AKI. The optimal cut-off was 0.73 with a gray zone ranging between 0.72 and 0.75.
authors.affiliation: Department of Anaesthesiology and Critical Care Medicine, Amiens University Hospital, Place Victor Pauchet, Amiens, France. Electronic address: guinotpierregregoire@gmail.com.
authors.forename: Pierre-Grégoire
authors.initials: PG
authors.lastname: Guinot
authors.forename: Eugénie
authors.initials: E
authors.lastname: Bernard
authors.forename: Osama
authors.initials: O
authors.lastname: Abou Arab
authors.forename: Louise
authors.initials: L
authors.lastname: Badoux
authors.forename: Momar
authors.initials: M
authors.lastname: Diouf
authors.forename: Elie
authors.initials: E
authors.lastname: Zogheib
authors.forename: Hervé
authors.initials: H
authors.lastname: Dupont
mesh_terms: D058186:Acute Kidney Injury / Q000000981:diagnostic imaging* / Q000453:epidemiology; D000368:Aged; D000369:Aged, 80 and over; D006348:Cardiac Surgical Procedures / Q000009:adverse effects*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012720:Severity of Illness Index; D018608:Ultrasonography, Doppler / Q000379:methods*
keywords: Doppler; acute kidney injury; cardiac surgical procedures; postoperative period; ultrasonography