Obstacles to reducing plasma levels of uremic solutes by hemodialysis

More intensive hemodialysis has provided limited clinical benefit. The lack of benefit may be due in part to the failure of intensive dialysis to reduce uremic solute levels in plasma. Two well-described factors limiting the reduction in these levels are the intermittency of dialysis treatment and the distribution of solutes in multiple body compartments. Efforts to increase the clearance of large solutes and protein-bound solutes have revealed two other considerations-the presence of nonrenal clearance and increases in solute generation. For β₂ microglobulin, a commonly measured large solute, nonrenal clearance limits reduction in its levels. For the bound solute p-cresol sulfate, an increase in generation appears to limit its reduction. A variety of factors likely determine the behavior of different solutes. More data on solute toxicity are needed as is better knowledge of solute kinetics. We will then be better able to design optimal therapeutic interventions. A combination of dialytic and nondialytic strategies may well be needed to reduce the plasma levels of toxic solutes and improve patients' health.