Small-solute and middle-molecule clearances during continuous flow peritoneal dialysis.

Previous theoretic and clinical studies have shown that continuous flow peritoneal dialysis (CFPD) provides a high dose of small-solute removal; however, the dose of middle-molecule removal with CFPD therapy has not been evaluated. We used a variable-volume, two-compartment model to calculate theoretical steady-state solute kinetic profiles during CFPD, continuous ambulatory peritoneal dialysis (CAPD), and hemodialysis using a high-flux dialyzer (HFHD), for an anuric 70-kg patient and two measures of dose: equivalent renal clearance (EKR) and standard Kt/V (stdKt/V). Dose measures during each therapy were calculated for five solutes: urea, creatinine, vitamin B12, inulin, and beta 2-microglobulin. Fluid (1 L daily) was assumed to accumulate in and to be removed from the extracellular space, and non renal clearance was assumed to be zero for all solutes except beta 2-microglobulin. Calculated doses for CFPD were higher than for CAPD or HFHD when assessed by either EKR or stdKt/V. Dose enhancements for CFPD were highest for small solutes, but were still considerable for middle molecules. We conclude that CFPD achieves higher doses than CAPD or HFHD for both small-solute and middle-molecule removal.