Three Versus 4 Daily Exchanges and Residual Kidney Function Decline in Incident CAPD Patients: A Randomized Controlled Trial.

BACKGROUND: Incident patients treated with continuous ambulatory peritoneal dialysis (CAPD) are often prescribed either 3 or 4 exchanges per day. However, the effects on residual kidney function and clinical outcomes of 3 versus 4 exchanges are not known.

STUDY DESIGN: Prospective, randomized, controlled, open-label study.

SETTING & PARTICIPANTS: Incident CAPD patients aged 18 to 80 years with glomerular filtration rates (GFRs; mean of renal urea and creatinine clearance from a 24-hour urine collection) ≥ 2mL/min and urine volume ≥ 500mL/d. Exclusion criteria included refusal for informed consent, history of maintenance hemodialysis therapy or transplantation, or limited life expectancy.

INTERVENTION: 24-month intervention with 3- or 4-exchange CAPD using glucose-based peritoneal dialysis fluids.

OUTCOMES: Primary outcomes were GFR, urine volume, and anuria-free survival. Secondary outcomes included peritonitis, patient survival, and technique survival.

RESULTS: The study recruited 139 patients, 70 in the 3-exchange group and 69 in the 4-exchange group. Baseline body mass indexes were 21.4±3.0 and 21.9±3.2kg/m2 for the 3- and 4-exchange groups, respectively (P=0.4). After 24 months, for 3 versus 4 exchanges, GFR (1.6±2.0 vs 1.7±1.9mL/min; P=0.8), urine volume (505±522 vs 474±442mL/d; P=0.8), and anuria-free survival (log-rank test statistic = 0.055; P=0.8) did not differ between groups, but Kt/V (1.95±0.39 vs 2.19±0.48; P=0.03) and ultrafiltration (404±499 vs 742±512mL/d; P=0.004) were lower in the 3-exchange group. The 3-exchange group had nominally longer peritonitis-free survival time (log-rank test statistic = 3.811; P=0.05), and nominally fewer patients had peritonitis in this group, though this was not statistically significant (13% vs 26%; P=0.06). Patient survival (log-rank test statistic = 0.978; P=0.3) and technique survival (log-rank test statistic = 0.347; P=0.6) were similar between groups.

LIMITATIONS: Single-center design; no formal sample-size calculations.

CONCLUSIONS: In this small trial, CAPD regimens with 3 and 4 exchanges had similar effects on residual GFR, urine volume, and time to anuria. Incremental peritoneal dialysis starts appear safe when patients are monitored.