title: Calcium mass balances during standard bicarbonate hemodialysis and long-hour slow-flow bicarbonate hemodialysis.
abstract: BACKGROUND
  Dialysate calcium (Ca) concentration should be viewed as part of the integrated therapeutic regimen to control renal osteodystrophy and maintain normal mineral metabolism. Thus, a correct ionized calcium mass balance (Ca++MB) during hemodialysis (HD) is crucial in the treatment of renal osteodystrophy. The GENIUS single-pass batch dialysis system (Fresenius Medical Care, Germany) consists of a closed dialysate tank of 90 L; it offers the opportunity of effecting mass balances of any solute in a very precise way.
  
  
  METHODS
  The present study has a crossover design: 11 stable anuric HD patients underwent 2 bicarbonate HD sessions, 1 of 4 hours (4h) and the other of 8 hours (8h) in a random sequence, always at the same interdialytic interval, at least 1 week apart. The GENIUS system and high-flux FX80 dialyzers (Fresenius Medical Care, Germany) were used. The volume of blood and dialysate processed, volume of ultrafiltration and dialysate Ca concentrations (1.50 mmol/L) were prescribed to be the same. Trends of plasma Ca++, blood pH and bicarbonates during dialysis, as well as Ca++MBs were determined. Plasma parathyroid hormone (PTH) levels at the start and end of the 2 treatments were measured.
  
  
  RESULTS
  Ca++MBs (mean ± SD) were +284.6 ± 137.4 mg and +297.7 ± 131.6 mg (p=0.307) in the 4h and 8h treatments, respectively. No single session out of the 22 had a negative Ca++MB for the patient. Mean plasma Ca++, blood pH and bicarbonate levels were not statistically significantly different when comparing the start and end of the sessions of the 2 treatments. Mean plasma Ca++, blood pH and bicarbonate levels increased significantly along the time points in both 4h and 8h HD sessions (repeated measures ANOVA: p<0.0001). Mean plasma PTH levels were not statistically significantly different when comparing the start and end of the sessions of the 2 treatments. The differences between predialysis and postdialysis plasma PTH levels were not statistically significantly different either in 4h or 8h sessions (Wilcoxon's test: p=NS), even though a trend toward lower postdialysis plasma PTH levels was observed in both 4h and 8h treatments.
  
  
  CONCLUSIONS
  Our data show incontrovertibly that, when dialyzing with a dialysate Ca concentration of 1.50 mmol/L, 4h standard bicarbonate HD and 8h slow-flow bicarbonate HD always achieve a quite similar positive Ca++MB for the patients.
authors.affiliation: Miulli General Hospital, Acquaviva delle Fonti, Italy. basile.miulli@libero.it
authors.forename: Carlo
authors.initials: C
authors.lastname: Basile
authors.forename: Pasquale
authors.initials: P
authors.lastname: Libutti
authors.forename: Anna Lucia
authors.initials: AL
authors.lastname: Di Turo
authors.forename: Sergio
authors.initials: S
authors.lastname: Tundo
authors.forename: Pasquale
authors.initials: P
authors.lastname: Maselli
authors.forename: Francesco
authors.initials: F
authors.lastname: Casucci
authors.forename: Nicola
authors.initials: N
authors.lastname: Losurdo
authors.forename: Annalisa
authors.initials: A
authors.lastname: Teutonico
authors.forename: Luigi
authors.initials: L
authors.lastname: Vernaglione
authors.forename: Carlo
authors.initials: C
authors.lastname: Lomonte
mesh_terms: D000328:Adult; D000368:Aged; D001639:Bicarbonates / Q000493:pharmacokinetics*; D002118:Calcium / Q000378:metabolism*; D012080:Chronic Kidney Disease-Mineral and Bone Disorder / Q000209:etiology / Q000517:prevention & control; D018592:Cross-Over Studies; D005260:Female; D015312:Hemodialysis Solutions; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008297:Male; D008875:Middle Aged; D010281:Parathyroid Hormone / Q000097:blood; D006435:Renal Dialysis / Q000379:methods*; D051437:Renal Insufficiency / Q000097:blood / Q000150:complications / Q000628:therapy*; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D001639:Bicarbonates; D015312:Hemodialysis Solutions; D010281:Parathyroid Hormone; D002118:Calcium