Exemplary compounds useful as an osmotic agent include those commonly used in peritoneal dialysis, such as dextrose and other sugars, as well as less common materials taught to be suitable for peritoneal dialysis, such as sugar polymers, synthetic non-calorigenic materials, such as saccharin, cyclamate, and aspartylphenylalanine methyl ester, commonly referred to as aspartame; amino acids, alpha-k