title: Effects of fluid administration on renal perfusion in critically ill patients.
abstract: BACKGROUND
  Fluid administration is a first-line therapy for acute kidney injury associated with circulatory failure. Although aimed at increasing renal perfusion in these patients, this intervention may improve systemic hemodynamics without necessarily ameliorating intrarenal flow distribution or urine output. We used Doppler techniques to investigate the effects of fluid administration on intrarenal hemodynamics and the relationship between changes in renal hemodynamics and urine output. We hypothesized that, compared to systemic hemodynamic variables, changes in renal hemodynamics would better predict increase in urine output after fluid therapy.
  
  
  METHODS
  We measured systemic hemodynamic variables and performed renal interlobar artery Doppler on both kidneys before and after volume expansion in 49 adult patients with acute circulatory failure. We measured systolic and diastolic velocities and computed the resistivity index (RI). We recorded urine output for 3 h before and after the fluid challenge.
  
  
  RESULTS
  Fluid administration resulted in a small but consistent decrease in RI (from 0.73 ± 0.09 to 0.71 ± 0.09, p < 0.01). There was a concomitant increase in mean arterial pressure (from 75 ± 15 to 80 ± 14 mmHg, p < 0.01), pulse pressure (49 ± 19 to 55 ± 19 mmHg, p < 0.01) and urine output (55 ± 76 to 81 ± 87 ml/hour, p < 0.01). Changes in RI were negatively correlated with changes in urine output and mean arterial pressure but not in pulse pressure. The increase in urine output was predicted by changes in RI but not by changes in systemic hemodynamics.
  
  
  CONCLUSIONS
  Changes in renal hemodynamics during a fluid challenge can be observed by Doppler ultrasonography before urine output increases. Moreover, these changes are better predictors of an increase in urine output than are mean arterial pressure and pulse pressure.
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. mmmouhamed@gmail.com.
authors.forename: Mouhamed Djahoum
authors.initials: MD
authors.lastname: Moussa
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. sabino.scolletta@unisi.it.
authors.forename: Sabino
authors.initials: S
authors.lastname: Scolletta
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. dfagnoul@ulb.ac.be.
authors.forename: David
authors.initials: D
authors.lastname: Fagnoul
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. pasquier9606@yahoo.fr.
authors.forename: Pierre
authors.initials: P
authors.lastname: Pasquier
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. Alexandre.Brasseur@erasme.ulb.ac.be.
authors.forename: Alexandre
authors.initials: A
authors.lastname: Brasseur
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. Fabio.Taccone@erasme.ulb.ac.be.
authors.forename: Fabio Silvio
authors.initials: FS
authors.lastname: Taccone
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. jlvincen@ulb.ac.be.
authors.forename: Jean-Louis
authors.initials: JL
authors.lastname: Vincent
authors.affiliation: Department of Intensive Care, Erasme University Hospital, Université Libre de Bruxelles, Brussels, Belgium. ddebacke@ulb.ac.be.
authors.forename: Daniel
authors.initials: D
authors.lastname: De Backer
mesh_terms: D058186:Acute Kidney Injury / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D000368:Aged; D016638:Critical Illness / Q000628:therapy*; D005260:Female; D005440:Fluid Therapy / Q000379:methods*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012079:Renal Circulation / Q000502:physiology*; D012769:Shock / Q000000981:diagnostic imaging / Q000503:physiopathology / Q000628:therapy*; D018608:Ultrasonography, Doppler / Q000379:methods