title: Ranking of factors determining potassium mass balance in bicarbonate haemodialysis.
abstract: BACKGROUND
  One of the most important pathogenetic factors involved in the onset of intradialysis arrhytmias is the alteration in electrolyte concentration, particularly potassium (K(+)).
  
  
  METHODS
  Two studies were performed: Study A was designed to investigate above all the isolated effect of the factor time t on intradialysis K(+) mass balance (K(+)MB): 11 stable prevalent Caucasian anuric patients underwent one standard (∼4 h) and one long-hour (∼8 h) bicarbonate haemodialysis (HD) session. The latter were pair-matched as far as the dialysate and blood volume processed (90 L) and volume of ultrafiltration are concerned. Study B was designed to identify and rank the other factors determining intradialysis K(+)MB: 63 stable prevalent Caucasian anuric patients underwent one 4-h standard bicarbonate HD session. Dialysate K(+) concentration was 2.0 mmol/L in both studies. Blood samples were obtained from the inlet blood tubing immediately before the onset of dialysis and at t60, t120, t180 min and at end of the 4- and 8-h sessions for the measurement of plasma K(+), blood bicarbonates and blood pH. Additional blood samples were obtained at t360 min for the 8 h sessions. Direct dialysate quantification was utilized for K(+)MBs. Direct potentiometry with an ion-selective electrode was used for K(+) measurements.
  
  
  RESULTS
  Study A: mean K(+)MBs were significantly higher in the 8-h sessions (4 h: -88.4 ± 23.2 SD mmol versus 8 h: -101.9 ± 32.2 mmol; P = 0.02). Bivariate linear regression analyses showed that only mean plasma K(+), area under the curve (AUC) of the hourly inlet dialyser diffusion concentration gradient of K(+) (hcgAUCK(+)) and AUC of blood bicarbonates and mean blood bicarbonates were significantly related to K(+)MB in both 4- and 8-h sessions. A multiple linear regression output with K(+)MB as dependent variable showed that only mean plasma K(+), hcgAUCK(+) and duration of HD sessions per se remained statistically significant. Study B: mean K(+)MBs were -86.7 ± 22.6 mmol. Bivariate linear regression analyses showed that only mean plasma K(+), hcgAUCK(+) and mean blood bicarbonates were significantly related to K(+)MB. Again, only mean plasma K(+) and hcgAUCK(+) predicted K(+)MB at the multiple linear regression analysis.
  
  
  CONCLUSIONS
  Our studies enabled to establish the ranking of factors determining intradialysis K(+)MB: plasma K(+) → dialysate K(+) gradient is the main determinant; acid-base balance plays a much less important role. The duration of HD session per se is an independent determinant of K(+)MB.
authors.affiliation: Division of Nephrology, Miulli General Hospital, Acquaviva delle Fonti, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Basile
authors.affiliation: Division of Nephrology, Miulli General Hospital, Acquaviva delle Fonti, Italy.
authors.forename: Pasquale
authors.initials: P
authors.lastname: Libutti
authors.affiliation: Division of Nephrology, Miulli General Hospital, Acquaviva delle Fonti, Italy.
authors.forename: Piero
authors.initials: P
authors.lastname: Lisi
authors.affiliation: Division of Nephrology, Miulli General Hospital, Acquaviva delle Fonti, Italy.
authors.forename: Annalisa
authors.initials: A
authors.lastname: Teutonico
authors.affiliation: Division of Nephrology, Perrino Hospital, Brindisi, Italy.
authors.forename: Luigi
authors.initials: L
authors.lastname: Vernaglione
authors.affiliation: Division of Nephrology, Miulli General Hospital, Acquaviva delle Fonti, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Casucci
authors.affiliation: Division of Nephrology, Miulli General Hospital, Acquaviva delle Fonti, Italy.
authors.forename: Carlo
authors.initials: C
authors.lastname: Lomonte
mesh_terms: D000136:Acid-Base Equilibrium; D001002:Anuria / Q000097:blood* / Q000473:pathology / Q000628:therapy; D019540:Area Under Curve; D001639:Bicarbonates / Q000493:pharmacokinetics*; D015314:Dialysis Solutions / Q000737:chemistry*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D011188:Potassium / Q000097:blood*; D012044:Regression Analysis; D006435:Renal Dialysis; D013997:Time Factors; D014018:Tissue Distribution
chemical_list: D001639:Bicarbonates; D015314:Dialysis Solutions; D011188:Potassium
keywords: acid-base balance; diffusion concentration gradient; haemodialysis; plasma potassium; potassium mass balance