BOUND SOLUTE DIALYSIS

Abstract

Bound solute dialysis (BSD), as practiced by MARS (“albumin dialysis”) and the Biologic-DT (“sorbent dialysis”), has shown potential efficacy in treatment of liver failure patients. The thermodynamic principles governing BSD are used to develop a comprehensive understanding of the process. The dimensionless parameters that govern BSD are: (1) Λ, the binding power of the solute binding moiety (2) κ, the membrane clearance/blood flow rate ratio (3) α, the dialysate/blood flow rate ratio and (4) β, the dialysate/blood binding moiety concentration ratio. Mathematical modeling of counter-current BSD indicates that for a given binding moiety (fixed Λ), the most important parameter for achieving high removal rates is the dialyzer clearance for free (unbound) solute. The results also show solute removal approaching an asymptote with increasing β that is dependent on κ and independent of α. More importantly, results indicate that once a dialysis membrane is chosen, solute removal is virtually independent of blood flow rate, dialysate flow rate, and amount of binding moiety in the dialysate provided the amount is greater than about 90% of that required to reach the asymptote. Experimental observations over a range of blood flow rates, 100 to 400 mL/min, dialysate flow rates, 50 to 400 mL/min, and dialysate/blood albumin concentration ratios, β = 0 to 0.3, corroborate the model predictions and indicate that less than 4 g/L albumin in the dialysate solution is all that is required for effective BSD. The experimental results also show evidence of enhanced clearance once the dialysis membrane pore structure surface saturates with albumin.