Session SB1.3

Model-Based Analysis of Na-K Pump Influence on Potassium Depuration during Hemodialysis

A Ciandrini*, S Severi, S Cavalcanti, F Fontanazzi,
F Grandi, A Santoro

Hospital S.p.A. Bologna
Bologna, Italy

Potassium ion (K+) kinetics in intra and extracellular compartments during hemodialysis was studied by means of a double-pool computer model which included potassium-dependent active transport (Na-K-ATPase pump). Thirty-four patients (21M/13F; aged 66±22 years old, dry weight 66±15 kg, height 163±10 cm) on renal replacement therapy with thrice weekly 4 hour double-needle hemodialysis were enrolled.
Each patient was studied during acetate free biofiltration (AFB) with a constant K+ dialysate concentration (KCONST therapy) and with a time-varying (profiled) K+ dialysate concentration (KPROF therapy). The two therapies induced different levels of K+ plasma concentration (KCONST: 3.7±0.9 vs. KPROF: 4.0±0.6 mmol/L, time-averaged values, p<0.01).
The computer model was tuned to accurately fit plasmatic K+ measured in the course and one hour after KCONST and KPROF 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 minutes of dialysis was mainly 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 KPROF vs 41±14% in KCONST.
These results suggest that the Na-K pump plays a major role in K+ apportionment between extracellular and intracellular compartments, and potassium dialysate concentration strongly influences pump activity. Moreover, this aspect can be important to understand and consequently control the resting membrane potential during the hemodialysis treatment in order to not affect the cardiac cell excitability of the patient. For this reason the computer-model here presented may represent a useful tool to quantitatively assess the impact of dialysate potassium on K+ kinetics in intra and extracellular compartments and to design dialysate potassium content tailored to the patient’s needs.

(Abstract Control Number: 119)