title: Doppler resistive index to reflect regulation of renal vascular tone during sepsis and acute kidney injury.
abstract: BACKGROUND
  Renal resistive index (RI), determined by Doppler ultrasonography, directly reveals and quantifies modifications in renal vascular resistance. The aim of this study was to evaluate if mean arterial pressure (MAP) is determinant of renal RI in septic, critically ill patients suffering or not from acute kidney injury (AKI).
  
  
  METHODS
  This prospective observational study included 96 patients. AKI was defined according to RIFLE criteria and transient or persistent AKI according to renal recovery within 3 days.
  
  
  RESULTS
  Median renal RIs were 0.72 (0.68-0.75) in patients without AKI and 0.76 (0.72-0.80) in patients with AKI (P = 0.001). RIs were 0.75 (0.72-0.79) in transient AKI and 0.77 (0.70-0.80) in persistent AKI (P = 0.84). RI did not differ in patients given norepinephrine infusion and was not correlated with norepinephrine dose. RI was correlated with MAP (ρ = -0.47; P = 0.002), PaO2/FiO2 ratio (ρ = -0.33; P = 0.04) and age (ρ = 0.35; P = 0.015) only in patients without AKI.
  
  
  CONCLUSIONS
  A poor correlation between renal RI and MAP, age, or PaO2/FiO2 ratio was found in septic and critically ill patients without AKI compared to patients with AKI. These findings suggest that determinants of RI are multiple. Renal circulatory response to sepsis estimated by Doppler ultrasonography cannot reliably be predicted simply from changes in systemic hemodynamics. As many factors influence its value, the interest in a single RI measurement at ICU admission to determine optimal MAP remains uncertain.
authors.forename: Antoine
authors.initials: A
authors.lastname: Dewitte
authors.forename: Julien
authors.initials: J
authors.lastname: Coquin
authors.forename: Bertrand
authors.initials: B
authors.lastname: Meyssignac
authors.forename: Olivier
authors.initials: O
authors.lastname: Joannès-Boyau
authors.forename: Catherine
authors.initials: C
authors.lastname: Fleureau
authors.forename: Hadrien
authors.initials: H
authors.lastname: Roze
authors.forename: Jean
authors.initials: J
authors.lastname: Ripoche
authors.forename: Gérard
authors.initials: G
authors.lastname: Janvier
authors.forename: Christian
authors.initials: C
authors.lastname: Combe
authors.forename: Alexandre
authors.initials: A
authors.lastname: Ouattara
mesh_terms: D058186:Acute Kidney Injury / Q000000981:diagnostic imaging* / Q000503:physiopathology; D000368:Aged; D001794:Blood Pressure / Q000502:physiology*; D005260:Female; D006801:Humans; D007668:Kidney / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D018805:Sepsis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D018608:Ultrasonography, Doppler / Q000379:methods