title: Model-based analysis of potassium removal during hemodialysis.
abstract: Potassium ion (K(+)) kinetics in intra- and extracellular compartments during dialysis was studied by means of a double-pool computer model, which included potassium-dependent active transport (Na-K-ATPase pump) in 38 patients undergoing chronic hemodialysis. Each patient was treated for 2 weeks with a constant K(+) dialysate concentration (K(+)(CONST) therapy) and afterward for 2 weeks with a time-varying (profiled) K(+) dialysate concentration (K(+)(PROF) therapy). The two therapies induced different levels of K(+) plasma concentration (K(+)(CONST): 3.71 +/- 0.88 mmol/L vs. K(+)(PROF): 3.97 +/- 0.64 mmol/L, time-averaged values, P < 0.01). The computer model was tuned to accurately fit plasmatic K(+) measured in the course and 1 h after K(+)(CONST) and K(+)(PROF) therapies and was then used to simulate the kinetics of intra- and extracellular K(+). Model-based analysis showed that almost all the K(+) removal in the first 90 min of dialysis was derived from the extracellular compartment. The different K(+) time course in the dialysate and the consequently different Na-K pump activity resulted in a different sharing of removed potassium mass at the end of dialysis: 56% +/- 17% from the extracellular compartment in K(+)(PROF) versus 41% +/- 14% in K(+)(CONST). At the end of both therapies, the K(+) distribution was largely unbalanced, and, in the next 3 h, K(+) continued to flow in the extracellular space (about 24 mmol). After rebalancing, about 80% of the K(+) mass that was removed derived from the intracellular compartment. In conclusion, the Na-K pump plays a major role in K(+) apportionment between extracellular and intracellular compartments, and potassium dialysate concentration strongly influences pump activity.
authors.affiliation: Department of Electronics, Computer Science and Systems, University of Bologna, Viale Risorgimento 2, Bologna, Italy. ciandrini.andrea@gmail.com
authors.forename: Andrea
authors.initials: A
authors.lastname: Ciandrini
authors.forename: Stefano
authors.initials: S
authors.lastname: Severi
authors.forename: Silvio
authors.initials: S
authors.lastname: Cavalcanti
authors.forename: Francesco
authors.initials: F
authors.lastname: Fontanazzi
authors.forename: Fabio
authors.initials: F
authors.lastname: Grandi
authors.forename: Michele
authors.initials: M
authors.lastname: Buemi
authors.forename: Carlo
authors.initials: C
authors.lastname: Mura
authors.forename: Pietro
authors.initials: P
authors.lastname: Bajardi
authors.forename: Fabio
authors.initials: F
authors.lastname: Badiali
authors.forename: Antonio
authors.initials: A
authors.lastname: Santoro
mesh_terms: D000328:Adult; D000368:Aged; D003198:Computer Simulation; D004058:Diffusion; D005260:Female; D015312:Hemodialysis Solutions / Q000737:chemistry / Q000378:metabolism / Q000627:therapeutic use*; D006706:Homeostasis; D006801:Humans; D007558:Italy; D007676:Kidney Failure, Chronic / Q000097:blood / Q000628:therapy*; D007700:Kinetics; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D017711:Nonlinear Dynamics; D011188:Potassium / Q000097:blood*; D006435:Renal Dialysis; D015203:Reproducibility of Results; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
chemical_list: D015312:Hemodialysis Solutions; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium