The impact of increasing the daytime dialysis exchange frequency on peritoneal dialysis adequacy and nutritional status of Chinese anuric patients

Abstract

Objective: To study the effect of increasing the daytime dialysis exchange frequency on dialysis adequacy and nutritional status of Chinese anuric patients. Setting: University teaching hospital. Patient: 100 anuric patients on continuous ambulatory peritoneal dialysis (CAPD). Design: 50 patients had one additional daytime 2-L exchange (intervention group); the dialysis regimen remained unchanged in the other 50 patients (control group). Outcome: Dialysis adequacy [Kt/V, weekly creatinine clearance (wCCr), and net ultrafiltration (UF)] and nutritional status [serum albumin, dietary protein intake, represented by normalized protein nitrogen appearance (nPNA), and percent lean body mass (%LBM)] were measured at 0 and 6 months. Results: Baseline dialysis adequacy and nutritional indices were comparable between the two groups. In the control group, all parameters remained stable at month 6. In the intervention group, there were significant increases in UF, Kt/V, wCCr, nPNA, and %LBM from months 0 to 6. The improvement in nPNA was affected by daily exchange volume. In 30 patients, the number of exchanges was increased from 3 to 4 per day; their Kt/V and nPNA rose significantly from month 0 to month 6. In the other 20 patients, the number of exchanges was increased from 4 to 5 per day; there was a significant increase in Kt/V but nPNA remained static. The change in nPNA correlated inversely with Kt/V at month 0 (Pearson's r = -0.352, p = 0.012). Multivariate analysis with a general linear model showed that age, Kt/V at month 0, and 3 dialysis exchanges per day at month 0 (versus 4 exchanges) were independent predictors of the change in nPNA. Conclusions: Increasing the number of peritoneal dialysis exchanges effectively increased Kt/V in Chinese anuric CAPD patients. However, the improvement in nPNA correlated inversely with baseline Kt/V. Although increasing the number of exchanges from 3 to 4 per day improved nPNA, increasing the number of daily exchanges beyond 4 may not improve nPNA further.