Solutes removal characteristics at various effluent rates during different continuous renal replacement therapy modalities

Some studies suggest the effluent as a surrogate solute removal indicator in continuous hemodialysis or hemofiltration, but the delivered clearance is frequently smaller than prescribed. This study aims at testing whether the effluent, represented by mL/kg/h, could measure solute clearance and whether increasing effluent increases clearance proportionately in continuous hemodialysis or hemofiltration. Patients treated with continuous renal replacement therapy for various diagnoses were included. The range of dialysate flow rate or substitution fluid flow rate was 1–5？L/h; solutes in the effluent and in the plasma entering the filter were measured, and the ratio of solutes in the effluent and in the plasma entering the filter and the clearance of blood urea nitrogen, creatinine, phosphate, and β2-microglobulin were calculated. The ratio of solutes in the effluent and in the plasma entering the filter showed a decreasing trend with increased dialysate flow rate or substitution fluid flow rate (p？<？0.05), but solute clearance showed an increasing trend. The increase in solute clearance was less than expected from the increased effluent (p？<？0.01), and actual delivered clearance was always below the corresponding prescribed clearance (p？<？0.001). With increasing prescribed clearance of continuous renal replacement therapy, effluent rate overestimated the delivered clearance