Journal
NEPHROLOGY DIALYSIS TRANSPLANTATION
Volume 30, Issue 3, Pages 505-513Publisher
OXFORD UNIV PRESS
DOI: 10.1093/ndt/gfu376
Keywords
acid-base balance; diffusion concentration gradient; haemodialysis; plasma potassium; potassium mass balance
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One of the most important pathogenetic factors involved in the onset of intradialysis arrhytmias is the alteration in electrolyte concentration, particularly potassium (K+). 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 (similar to 4 h) and one long-hour (similar to 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 t(60), t(120), t(180) 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 t(360) 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. 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. 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.
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