title: Bedside estimation of absolute renal blood flow and glomerular filtration rate in the intensive care unit. A validation of two independent methods.
abstract: OBJECTIVE
  To evaluate various treatment strategies in critically ill patients with ischaemic acute renal failure, there is a need for reliable bedside measurements of total renal blood flow (RBF), glomerular filtration rate (GFR) and renal oxygen consumption without the need for urine collection.
  
  
  METHODS
  The continuous renal vein thermodilution method and the infusion clearance techniques were validated against the gold standard technique, the urinary clearance of paraaminohippurate (PAH) and chromium ethylenediaminetetraacetic acid, respectively.
  
  
  METHODS
  University hospital cardiothoracic ICU.
  
  
  METHODS
  Seventeen uncomplicated mechanically ventilated post-cardiac surgical patients.
  
  
  METHODS
  None.
  
  
  RESULTS
  Renal blood flow, GFR and the renal filtration fraction (FF) were measured for two consecutive 30-min periods by urinary clearance and compared with simultaneous measurements made by the thermodilution and infusion clearance techniques. Urinary clearance for PAH was corrected for by renal extraction of PAH. The within-group error, repeatability coefficient and the coefficient of variation were highest for the thermodilution technique and lowest for the infusion clearance technique with regard to RBF, GFR and FF. The infusion clearance technique had a higher agreement with the urinary clearance method than the thermodilution method. For estimations of RBF and GFR, the between-group errors were 33% and 43% comparing infusion clearance with urinary clearance and 65% and 67% comparing thermodilution with urinary clearance.
  
  
  CONCLUSIONS
  The infusion clearance method had the highest reproducibility and the highest agreement with the urinary clearance reference method. The renal vein thermodilution technique is less reliable in the ICU setting due to poor repeatability and poor agreement with the reference method.
authors.affiliation: Department of Cardiothoracic Anaesthesia and Intensive Care, Sahlgrenska University Hospital Göteborg, 41345 Göteborg, Sweden.
authors.forename: Kristina
authors.initials: K
authors.lastname: Swärd
authors.forename: Felix
authors.initials: F
authors.lastname: Valsson
authors.forename: Johan
authors.initials: J
authors.lastname: Sellgren
authors.forename: Sven-Erik
authors.initials: SE
authors.lastname: Ricksten
mesh_terms: D000368:Aged; D002857:Chromium; D003422:Critical Care; D005260:Female; D005466:Fluorocarbons; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D007362:Intensive Care Units; D007678:Kidney Glomerulus / Q000098:blood supply / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011182:Postoperative Care; D012079:Renal Circulation / Q000502:physiology*; D013815:Thermodilution / Q000379:methods
chemical_list: D005466:Fluorocarbons; D002857:Chromium; C015077:chromin