title: A regenerable potassium and phosphate sorbent system to enhance dialysis efficacy and device portability: a study in awake goats.
abstract: BACKGROUND
  Patients on standard intermittent haemodialysis suffer from strong fluctuations in plasma potassium and phosphate. Prolonged dialysis with a wearable device, based on continuous regeneration of a small volume of dialysate using ion exchangers, could moderate these fluctuations and offer increased clearance of these electrolytes. We report in vivo results on the efficacy of potassium and phosphate adsorption from a wearable dialysis device. We explore whether equilibration of ion exchangers at physiological Ca 2+ , Mg 2+ and hypotonic NaCl can prevent calcium/magnesium adsorption and net sodium release, respectively. Effects on pH and HCO3- were studied.
  
  
  METHODS
  Healthy goats were instrumented with a central venous catheter and dialysed. Potassium and phosphate were infused to achieve plasma concentrations commonly observed in dialysis patients. An adsorption cartridge containing 80 g sodium poly(styrene-divinylbenzene) sulphonate and 40 g iron oxide hydroxide beads for potassium and phosphate removal, respectively, was incorporated in a dialysate circuit. Sorbents were equilibrated and regenerated with a solution containing NaCl, CaCl 2 and MgCl 2 . Blood was pumped over a dialyser and dialysate was recirculated over the adsorption cartridge in a countercurrent direction.
  
  
  RESULTS
  Potassium and phosphate adsorption was 7.7 ± 2.7 and 4.9 ± 1.3 mmol in 3 h, respectively. Adsorption capacity remained constant during consecutive dialysis sessions and increased with increasing K + and PO43-. Equilibration at physiological Ca 2+ and Mg 2+ prevented net adsorption, eliminating the need for post-cartridge calcium and magnesium infusion. Equilibration at hypotonic NaCl prevented net sodium release Fe 2+ and arterial pH did not change. Bicarbonate was adsorbed, which could be prevented by equilibrating at HCO3- 15 mM.
  
  
  CONCLUSIONS
  We demonstrate clinically relevant, concentration-dependent, pH-neutral potassium and phosphate removal in vivo with small volumes of regenerable ion exchangers in our prototype wearable dialysis device. Application of the selected ion exchangers for potassium and phosphate removal in a wearable dialysis device appears to be effective with a low-risk profile.
authors.affiliation: Department of Nephrology and Hypertension, Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Maarten
authors.initials: M
authors.lastname: Wester
authors.affiliation: Department of Nephrology and Hypertension, Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Karin G
authors.initials: KG
authors.lastname: Gerritsen
authors.affiliation: Nanodialysis BV, Oirschot, The Netherlands.
authors.forename: Frank
authors.initials: F
authors.lastname: Simonis
authors.affiliation: Department of Nephrology and Hypertension, Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Walther H
authors.initials: WH
authors.lastname: Boer
authors.affiliation: Department of Nephrology and Hypertension, Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Diënty H
authors.initials: DH
authors.lastname: Hazenbrink
authors.affiliation: Central Laboratory Animal Research Facility, Utrecht University, Utrecht, The Netherlands.
authors.forename: Koen R
authors.initials: KR
authors.lastname: Vaessen
authors.affiliation: Department of Nephrology and Hypertension, Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Verhaar
authors.affiliation: Department of Nephrology and Hypertension, Regenerative Medicine Center Utrecht, University Medical Center Utrecht, Utrecht, The Netherlands.
authors.forename: Jaap A
authors.initials: JA
authors.lastname: Joles
mesh_terms: D000327:Adsorption; D000818:Animals; D001639:Bicarbonates / Q000097:blood; D017743:Equipment Reuse; D005290:Ferric Compounds / Q000737:chemistry; D006041:Goats; D006801:Humans; D007474:Ion Exchange; D008274:Magnesium / Q000097:blood; D010710:Phosphates / Q000097:blood / Q000302:isolation & purification*; D011188:Potassium / Q000097:blood / Q000302:isolation & purification*; D058996:Quality Improvement; D006435:Renal Dialysis / Q000295:instrumentation* / Q000379:methods; D012964:Sodium / Q000737:chemistry
chemical_list: D001639:Bicarbonates; D005290:Ferric Compounds; D010710:Phosphates; C000499:ferric oxide; D012964:Sodium; D008274:Magnesium; D011188:Potassium
keywords: animal trial; dialysate regeneration; haemodialysis; sorbent-based dialysis; wearable artificial kidney