25 June 2001
Background/Aim: Sodium and water retention is common in peritoneal dialysis patients and contributes to cardiovascular disease. As peritoneal sodium removal depends partly on dwell time, and automated peritoneal dialysis (APD) often uses short dwell time exchanges, the aim of this study was to compare the 24-hour peritoneal sodium removal in APD and standard continuous ambulatory peritoneal dialysis (CAPD) patients and to analyze its possible influence on blood pressure control. Methods: A total of 53 sodium balance studies (30 in APD and 23 in CAPD) were performed in 36 stable peritoneal dialysis patients. The 24-hour net removal of sodium was calculated as follows: M = ViCi – VdCd, where Vd is the 24-hour drained volume, Cd is the solute sodium concentration in Vd, Vi is the amount of solution used during a 24-hour period, and Ci is the sodium concentration in Vi. Peritoneal sodium removal was compared between APD and CAPD patients. Residual renal function, serum sodium concentration, daily urinary sodium losses, weekly peritoneal Kt/V and creatinine clearance, 4-hour dialysate/plasma creatinine ratio, proportion of hypertonic solutions, net ultrafiltration, systolic and diastolic blood pressures, and need for antihypertensive therapy were also compared between the groups. Results: Peritoneal sodium removal was higher (p < 0.001) in CAPD than in APD patients. There were no significant differences in residual renal function, serum sodium concentration, urinary sodium losses, peritoneal urea or creatinine clearances, 4-hour dialysate/plasma creatinine ratio, or proportion of hypertonic solutions between groups. The net ultrafiltration was higher in CAPD patients and correlated strongly (r = 0.82; p < 0.001) with peritoneal sodium removal. In APD patients, peritoneal sodium removal increased significantly only in those patients with a second daytime exchange. The systolic blood pressure was higher (p < 0.05) in APD patients, and the proportion of patients with antihypertensive therapy was also higher in APD patients, although no significant relationship between blood pressure values and amount of peritoneal sodium removal was found. Conclusions: The 24-hour sodium removal is higher in CAPD than in APD patients, and there is a trend towards better hypertension control in CAPD patients. As hypertension control and volume status are important indices of peritoneal dialysis adequacy, our results have to be considered in the choice of the peritoneal dialysis modality.