Comparison of sodium removal in peritoneal dialysis patients treated by continuous ambulatory and automated peritoneal dialysis

BACKGROUND: Optimal fluid balance for peritoneal dialysis (PD) patients requires both water and sodium removal. Previous studies have variously reported that continuous ambulatory peritoneal dialysis (CAPD) removes more or equivalent amounts of sodium than automated PD (APD) cyclers. We therefore wished to determine peritoneal dialysate losses with different PD treatments. METHODS: Peritoneal and urinary sodium losses were measured in 24-h collections of urine and PD effluent in patients attending for their first assessment of peritoneal membrane function. We adjusted fluid and sodium losses for CAPD patients for the flush before fill technique. RESULTS: We reviewed the results from 659 patients, mean age 57 ± 16 years, 56.3% male, 38.9% diabetic, 24.0% treated by CAPD, 22.5% by APD and 53.5% APD with a day-time exchange, with icodextrin prescribed to 72.8% and 22.7 g/L glucose to 31.7%. Ultrafiltration was greatest for CAPD 650 (300-1100) vs 337 (103-598) APD p < 0.001, vs 474 (171-830) mL/day for APD with a day exchange. CAPD removed most sodium 79 (33-132) vs 23 (- 2 to 51) APD p < 0.001, and 51 (9-91) for APD with a day exchange, and after adjustment for the CAPD flush before fill 57 (20-113), p < 0.001 vs APD. APD patients with a day exchanged used more hypertonic glucose dialysates [0 (0-5) vs CAPD 0 (0-1) L], p < 0.001. CONCLUSION: CAPD provides greater ultrafiltration and sodium removal than APD cyclers, even after adjusting for the flush-before fill, despite greater hypertonic usage by APD cyclers. Ultrafiltration volume and sodium removal were similar between CAPD and APD with a day fill