title: The faster potassium-lowering effect of high dialysate bicarbonate concentrations in chronic haemodialysis patients.
abstract: BACKGROUND
  Hyperkalaemia is common in patients with advanced renal disease. In this double-blind, randomized, three-sequence, crossover study, we compared the effect of three dialysate bicarbonate concentrations ([HCO3-]) on the kinetics of serum potassium (K+) reduction during a conventional haemodialysis (HD) session in chronic HD patients.
  
  
  METHODS
  We studied eight stable HD patients. The choice of dialysate [HCO3-] followed a previously assigned treatment protocol and the [HCO3-] used were low bicarbonate (LB; 27 mmol/l), standard bicarbonate (SB; 35 mmol/l) and high bicarbonate (HB; 39 mmol/l). Polysulphone dialysers and automated machines provided blood flow rates of 300 ml/min and dialysis flow rates of 500 ml/min for each HD session. Blood samples were drawn at 0 (baseline), 15, 30, 60 and 240 min from the arterial extracorporeal line to assess blood gases and serum electrolytes. In three of the eight patients, we measured serum K+ 1 h post-dialysis as well as K+ removal by the dialysis. The same procedures were followed until the completion of the three arms of the study, with a 1 week interval between each experimental arm.
  
  
  RESULTS
  Serum K+ decreased from 5.4+/-0.26 (baseline) to 4.96+/-0.20, 4.90+/-0.19, 4.68+/-0.13 and 4.24+/-0.15 mmol/l at 15, 30, 60 and 240 min, respectively, with LB; from 5.38+/-0.21 to 5.01+/-0.23, 4.70+/-0.25, 4.3+/-0.15 and 3.8+/-0.19 mmol/l, respectively, with SB; and from 5.45+/-0.25 to 4.79+/-0.17, 4.48+/-0.17, 3.86+/-0.16 and 3.34+/-0.11 mmol/l, respectively, with HB (P<0.05 for high vs standard and low [HCO3-] at 60 and 240 min). The decrease in serum K+ correlated with the rise in serum [HCO3-] in all but LB (P<0.05). Potassium rebound was 3.9+/-10.2%, 5.2+/-6.6% and 8.9+/-4.9% for LB, SB and HB dialysates, respectively (P=NS), while total K+ removal (mmol/dialysis) was 116.4+/-21.6 for LB, 73.2+/-12.8 for SB and 80.9+/-15.4 for HB (P=NS).
  
  
  CONCLUSIONS
  High dialysate [HCO3-] was associated with a faster decrease in serum K+. Our results strongly suggest that this reduction was due to the enhanced shifting of K+ from the extracellular to the intracellular fluid compartment rather than its removal by dialysis. This finding could have an impact for those patients with life-threatening pre-HD hyperkalaemia.
authors.affiliation: Unidad de Nefrología, Hospital Juan A. Fernández, Paraguay 5259 Piso 3 Apt A, C1425BTG Buenos Aires, Argentina. rheguilen@hotmail.com
authors.forename: Ricardo M
authors.initials: RM
authors.lastname: Heguilén
authors.forename: Claudia
authors.initials: C
authors.lastname: Sciurano
authors.forename: Angel D
authors.initials: AD
authors.lastname: Bellusci
authors.forename: Paula
authors.initials: P
authors.lastname: Fried
authors.forename: Graciela
authors.initials: G
authors.lastname: Mittelman
authors.forename: Guillermo
authors.initials: G
authors.lastname: Rosa Diez
authors.forename: Amelia R
authors.initials: AR
authors.lastname: Bernasconi
mesh_terms: D000136:Acid-Base Equilibrium / Q000187:drug effects; D000328:Adult; D001639:Bicarbonates / Q000032:analysis / Q000494:pharmacology*; D002021:Buffers; D018592:Cross-Over Studies; D004311:Double-Blind Method; D015312:Hemodialysis Solutions / Q000737:chemistry* / Q000494:pharmacology*; D006801:Humans; D007676:Kidney Failure, Chronic / Q000097:blood* / Q000628:therapy; D008875:Middle Aged; D011188:Potassium / Q000097:blood* / Q000493:pharmacokinetics; D006435:Renal Dialysis
chemical_list: D001639:Bicarbonates; D002021:Buffers; D015312:Hemodialysis Solutions; D011188:Potassium