title: Determination of extracellular fluid volume in healthy and azotemic cats.
abstract: BACKGROUND
  Methods for determining extracellular fluid volume (ECFV) are important clinically for cats. Bromide dilution has been studied in cats to estimate ECFV. Markers of GFR also distribute in ECFV and can be used for its measurement.
  
  
  OBJECTIVE
  The primary objective was to develop a method of determining ECFV from iohexol clearance in cats and evaluate agreement with that determined using bromide dilution. Additional objectives were to compare ECFV between azotemic and nonazotemic cats and evaluate appropriate methods of standardizing ECFV.
  
  
  METHODS
  Client-owned cats with varying renal function.
  
  
  METHODS
  Validation of ECFV determined from slope-intercept iohexol clearance was performed in 18 healthy nonazotemic cats. ECFV was then determined using the validated method and bromide dilution and agreement assessed. Appropriateness of standardization to body weight (BW) and body surface area (BSA) was evaluated.
  
  
  RESULTS
  Extracellular fluid volume determined from slope-intercept iohexol clearance and bromide dilution was 0.84 ± 0.32 L and 0.85 ± 0.19 L (mean ± SD), respectively. There were wide limits of agreement between the methods (-0.58 to 0.54 L) and therefore, agreement was considered to be poor. ECFV did not differ significantly between azotemic and nonazotemic cats (P = .177). BSA was found to be the best method for standardizing ECFV measurement in cats.
  
  
  CONCLUSIONS
  This study developed a method for determining ECFV from slope-intercept iohexol clearance which provides simultaneous assessment of renal function and an estimate of ECFV. ECFV does not differ between azotemic and nonazotemic cats, which suggests fluid volume loss or overload is not an important clinical feature in cats with mild chronic kidney disease.
authors.affiliation: Royal Veterinary College, London, UK.
authors.forename: N C
authors.initials: NC
authors.lastname: Finch
authors.forename: R
authors.initials: R
authors.lastname: Heiene
authors.forename: J
authors.initials: J
authors.lastname: Elliott
authors.forename: H M
authors.initials: HM
authors.lastname: Syme
authors.forename: A M
authors.initials: AM
authors.lastname: Peters
mesh_terms: D000818:Animals; D053099:Azotemia / Q000662:veterinary*; D001965:Bromides / Q000493:pharmacokinetics; D002371:Cat Diseases / Q000378:metabolism*; D002415:Cats; D045604:Extracellular Fluid / Q000502:physiology*; D005919:Glomerular Filtration Rate / Q000662:veterinary; D007472:Iohexol / Q000493:pharmacokinetics; D007668:Kidney / Q000378:metabolism
chemical_list: D001965:Bromides; D007472:Iohexol
keywords: Bromide; Glomerular filtration rate; Iohexol; Kidney disease; Renal