title: Ionic dialysance allows an adequate estimate of urea distribution volume in hemodialysis patients.
abstract: BACKGROUND
  An adequate estimation of urea distribution volume (V) in hemodialysis patients is useful to monitor protein nutrition. Direct dialysis quantification (DDQ) is the gold standard for determining V, but it is impractical for routine use because it requires equilibrated postdialysis plasma water urea concentration. The single pool variable volume urea kinetic model (SPVV-UKM), recommended as a standard by Kidney Disease Outcomes Quality Initiative (K/DOQI), does not need a delayed postdialysis blood sample but it requires a correct estimate of dialyser urea clearance.
  
  
  METHODS
  Ionic dialysance (ID) may accurately estimate dialyzer urea clearance corrected for total recirculation. Using ID as input to SPVV-UKM, correct V values are expected when end-dialysis plasma water urea concentrations are determined in the end-of-session blood sample taken with the blood pump speed reduced to 50 mL/min for two minutes (U(pwt2')). The aim of this study was to determine whether the V values determined by means of SPVV-UKM, ID, and U(pwt2') (V(ID)) are similar to those determined by the "gold standard" DDQ method (V(DDQ)). Eighty-two anuric hemodialysis patients were studied.
  
  
  RESULTS
  V(DDQ) was 26.3 +/- 5.2 L; V(ID) was 26.5 +/- 4.8 L. The (V(ID)-V(DDQ)) difference was 0.2 +/- 1.6 L, which is not statistically significant (P= 0.242). Anthropometric volume (V(A)) calculated using Watson equations was 33.6 +/- 6.0 L. The (V(A)-V(DDQ)) difference was 7.3 +/- 3.3 L, which is statistically significant (P < 0.001).
  
  
  CONCLUSIONS
  Anthropometric-based V values overestimate urea distribution volume calculated by DDQ and SPVV-UKM. ID allows adequate V values to be determined, and circumvents the problem of delayed postdialysis blood samples.
authors.affiliation: Department of Nephrology and Dialysis, A. Manzoni Hospital, Lecco, Italy. s.difilippo@ospedale.lecco.it
authors.forename: Salvatore
authors.initials: S
authors.lastname: Di Filippo
authors.forename: Celestina
authors.initials: C
authors.lastname: Manzoni
authors.forename: Simeone
authors.initials: S
authors.lastname: Andrulli
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pontoriero
authors.forename: Cesare
authors.initials: C
authors.lastname: Dell'Oro
authors.forename: Vincenzo
authors.initials: V
authors.lastname: La Milia
authors.forename: Flavia
authors.initials: F
authors.lastname: Tentori
authors.forename: Monica
authors.initials: M
authors.lastname: Crepaldi
authors.forename: Maria Carla
authors.initials: MC
authors.lastname: Bigi
authors.forename: Francesco
authors.initials: F
authors.lastname: Locatelli
mesh_terms: D015312:Hemodialysis Solutions / Q000378:metabolism; D006801:Humans; D007676:Kidney Failure, Chronic / Q000628:therapy*; D008954:Models, Biological; D012015:Reference Standards; D006435:Renal Dialysis / Q000379:methods* / Q000592:standards*; D014508:Urea / Q000378:metabolism
chemical_list: D015312:Hemodialysis Solutions; D014508:Urea