1. Six patients established on continuous ambulatory peritoneal dialysis entered a trial of treatment with dialysis fluid containing glycerol instead of glucose as the osmotic agent in an attempt to decrease the energy load. They were observed for a further 6 months after reconversion to glucose-based dialysis.
2. During the 6 month control period fluid balance was achieved mainly with a solution containing 76 mmol of glucose/l. Fluid balance was maintained during the 6 month period of treatment with glycerol only by the increased use of solutions containing a high concentration of glycerol (152 mmol/l and 272 mmol/l). Thus the energy value of the absorbed osmotic agent did not differ at a mean of 1607 kJ (384 kcal)/day using glycerol and 1669 kJ (399 kcal)/day using glucose as the osmotic agent.
3. In five subjects, fasting and peak blood glycerol levels did not change over the 6 months, but one subject, who accumulated glycerol, developed symptoms of hyperosmolality after 2 months and glycerol therapy was discontinued. In a further subject glycerol-based dialysis was terminated at 3 months when increasing angina was reported.
4. Mean fasting plasma triglyceride concentrations were 50% higher during the 6 months on glycerol (3.12 ± 1.12 mmol/l) than on glucose (2.19 ± 0.97 mmol/l) (P < 0.05). There was a small rise in very low density lipoprotein-cholesterol concentrations with glycerol dialysis but total cholesterol levels were unchanged.
5. The absorption of glycerol was not associated with an acute rise in circulating glucose or insulin but the mean blood glucose, over a 6 h dialysis cycle, had risen by 0.5 mmol/l after 3 months' treatment with glycerol and the mean serum insulin had risen from 5.9 ± 0.7 m-units/l to 9.8 ± 0.6 m-units/l (P < 0.01).
6. This study demonstrated no substantial advantage of glycerol over glucose as an osmotic agent in non-diabetic patients on continuous ambulatory peritoneal dialysis.