Influence of continuous ambulatory peritoneal dialysis on the anemia of endstage renal disease.

To evaluate the effect of continuous ambulatory peritoneal dialysis (CAPD) on the anemia of endstage renal disease, serial measurements of red cell mass and other hematological parameters were performed in 34 patients. Twenty-five patients were measured at the start and at 6 months (group 1), 13 at the start, at 6 and 12 months (group 2), and 11 were followed during their second year of treatment with measurements at 12, 18, and 24 months (group 3). In group 1 the hematocrit rose from 24.6 +/- 0.9 to 29.9 +/- 0.8% (P less than 0.01). The red cell mass increased from 879 +/- 44 to 1019 +/- 47 ml (P less than 0.01). The calculated plasma volume decreased from 2915 +/- 174 to 2568 +/- 136 ml (P less than 0.01). In group 2 at 6 months the hematocrit rose from 24.7 +/- 1.2 to 30.7 +/- 1.0% (P less than 0.01); the red cell mass increased from 924 +/- 66 to 1059 +/- 71 ml (P less than 0.05). The calculated plasma volume decreased at 6 months from 3001 +/- 201 to 2555 +/- 170 ml (P less than 0.01). No significant changes occurred between 6 and 12 months. In group 3 no significant changes in hematocrit, red cell mass, or plasma volume were observed. It is concluded that the rise in hematocrit in CAPD patients is due to an increase in red cell mass and also to a decrease in plasma volume. These changes are manifest within 6 months of treatment. The rise in red cell mass represents an improvement in renal anemia in these patients.