Renal replacement therapy (dialysis) is based on each of the following principles EXCEPT:
a) Pressure-related movement of solute across a semipermeable membrane
b) Evaporation of solvent to reduce the total patient volume
c) Pressure-related movement of solvent across a semipermeable membrane
d) Normalization of electrolytes due to diffusion
Answer b. Diffusion is the underlying principle behind renal replacement therapies. In addition to diffusion, solute (convection) and solvent (ultrafiltration) may be moved against a concentration gradient by manipulations of pressure gradients. All forms of dialysis generally occur in a closed system (including peritoneal dialysis); evaporative losses are minimal and do not contribute significantly to the observed effects of dialysis.