title: Ionic dialysance as a method for the on-line monitoring of delivered dialysis without blood sampling.
abstract: BACKGROUND
  It is well known that the difference between prescribed and delivered dialysis doses greatly affects the morbidity and mortality of dialysed patients. The on-line monitoring of delivered dialysis is therefore of paramount importance. Recently, a conductivity-based method for determining Kt/V on routine basis has been proposed.
  
  
  METHODS
  The study was performed using a specially designed module (Biofeedback Module, COT, Hospal) which, when connected to a dialysis monitor, automatically determines effective ionic dialysance (ID). During three consecutive dialysis sessions, administered to each of eight patients at the same depurative efficiency, we determined Kt/V by using mean effective ionic dialysance and by assuming, as suggested, that urea distribution volume corresponded to 55% of body weight. This method was compared with the gold standard of the direct quantification method. The Kt/V was also calculated by using mean effective ionic dialysance and the volume of urea distribution derived from anthropometric parameters.
  
  
  RESULTS
  The Kt/V determined by using mean effective ionic dialysance and by assuming that urea distribution volume corresponded to 55% of body weight was heavily underestimated (-22%). This difference was due to both the overestimate of urea distribution volume (+17%) and underestimate of effective urea clearance (KUeff) (-11%). The mean Kt/V calculated on the basis of ionic dialysance and anthropometric volume was also underestimated (-23%) since this volume was overestimated (+17%). Nevertheless, ionic dialysance and urea clearance proved to be closely correlated (r2 = 0.89) so that effective urea clearance can be derived according to: Kueff = ID x 0.865 + 39.89.
  
  
  CONCLUSIONS
  In steady-state patients, once urea distribution volume has been correctly determined by means of direct quantification, effective urea clearance can be easily derived from ionic dialysance and Kt/V calculated on-line at each session, without blood sampling or any additional costs.
authors.affiliation: Department of Nephrology and Dialysis, Lecco Hospital, Italy.
authors.forename: C
authors.initials: C
authors.lastname: Manzoni
authors.forename: S
authors.initials: S
authors.lastname: Di Filippo
authors.forename: M
authors.initials: M
authors.lastname: Corti
authors.forename: F
authors.initials: F
authors.lastname: Locatelli
mesh_terms: D005069:Evaluation Studies as Topic; D015312:Hemodialysis Solutions / Q000737:chemistry; D006801:Humans; D007477:Ions; D008991:Monitoring, Physiologic / Q000592:standards / Q000706:statistics & numerical data; D009862:Online Systems; D006435:Renal Dialysis / Q000379:methods* / Q000592:standards; D014508:Urea / Q000378:metabolism
chemical_list: D015312:Hemodialysis Solutions; D007477:Ions; D014508:Urea