title: Phosphate, urea and creatinine clearances: haemodialysis adequacy assessed by weekly monitoring.
abstract: BACKGROUND
  The specific distribution of phosphate and the control mechanisms for its plasma level makes phosphate kinetics during haemodialysis (HD) considerably different from those of urea and creatinine and makes the quantitative evaluation of adequacy of phosphate removal difficult. We propose the application of equivalent continuous clearance (ECC) as a phosphate adequacy parameter and compare it with ECC for creatinine and urea.
  
  
  METHODS
  Three consecutive dialysis sessions were evaluated for 25 patients on maintenance HD. Concentrations of phosphate, urea and creatinine in plasma were measured every 1h during the treatment and 45 min after, and every 30 min in dialysate. ECC was calculated using the removed solute mass assessed in dialysate and weekly solute profile in plasma. Similar calculations were performed also for the midweek dialysis session only. Different versions of the reference concentration for ECC were applied.
  
  
  RESULTS
  ECC with peak average reference concentration was 5.4 ± 1.0 for phosphate, 7.0 ± 1.0 for urea and 4.7 ± 1.0 mL/min for creatinine. ECC for urea and creatinine were well correlated in contrast to the correlations of ECC for phosphate versus urea and creatinine. Midweek ECC were higher than weekly ECC, but they were well correlated for urea and creatinine, but only weakly for phosphate.
  
  
  CONCLUSIONS
  HD adequacy monitoring for phosphate may be performed using ECC, but it is less predictable than similar indices for urea and creatinine. The values of ECC for phosphate are within the range expected for its molecular size compared with those for urea and creatinine.
authors.affiliation: Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Malgorzata
authors.initials: M
authors.lastname: Debowska
authors.affiliation: Department of Physical Therapy and Rehabilitation, Medical University of Lublin, Lublin, Poland.
authors.forename: Alicja
authors.initials: A
authors.lastname: Wojcik-Zaluska
authors.affiliation: Department of Nephrology, Medical University of Lublin, Lublin, Poland.
authors.forename: Andrzej
authors.initials: A
authors.lastname: Ksiazek
authors.affiliation: Department of Nephrology, Medical University of Lublin, Lublin, Poland.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Zaluska
authors.affiliation: Institute of Biocybernetics and Biomedical Engineering, Polish Academy of Sciences, Warsaw, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Waniewski
mesh_terms: D003404:Creatinine / Q000097:blood*; D015314:Dialysis Solutions / Q000032:analysis*; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D010710:Phosphates / Q000097:blood*; D006435:Renal Dialysis / Q000592:standards*; D014508:Urea / Q000097:blood*
chemical_list: D015314:Dialysis Solutions; D010710:Phosphates; D014508:Urea; D003404:Creatinine
keywords: EKR; KT/V; equivalent continuous clearance, ECC; haemodialysis adequacy; mineral metabolism