Effect of frequent hemodialysis on residual kidney function

Abstract

Frequent hemodialysis can alter volume status, blood pressure, and the concentration of osmotically active solutes, each of which might affect residual kidney function (RKF). In the Frequent Hemodialysis Network Daily and Nocturnal Trials, we examined the effects of assignment to six compared with three-times-per-week hemodialysis on follow-up RKF. In both trials, baseline RKF was inversely correlated with number of years since onset of ESRD. In the Nocturnal Trial, 63 participants had non-zero RKF at baseline (mean urine volume 0.76 liter/day, urea clearance 2.3 ml/min, and creatinine clearance 4.7 ml/min). In those assigned to frequent nocturnal dialysis, these indices were all significantly lower at month 4 and were mostly so at month 12 compared with controls. In the frequent dialysis group, urine volume had declined to zero in 52% and 67% of patients at months 4 and 12, respectively, compared with 18% and 36% in controls. In the Daily Trial, 83 patients had non-zero RKF at baseline (mean urine volume 0.43 liter/day, urea clearance 1.2 ml/min, and creatinine clearance 2.7 ml/min). Here, treatment assignment did not significantly influence follow-up levels of the measured indices, although the range in baseline RKF was narrower, potentially limiting power to detect differences. Thus, frequent nocturnal hemodialysis appears to promote a more rapid loss of RKF, the mechanism of which remains to be determined. Whether RKF also declines with frequent daily treatment could not be determined.

Figure 1

Regression analysis of baseline urine volume as a function of ESRD vintage for the Nocturnal and Daily Trials. The drawn curves were fit using locally weighted least squares regression. The Spearman correlations between vintage and baseline urine volume were −0.49 (p < 0.0001) in the Daily Trial, and −0.53 (p < 0.0001) in the Nocturnal Trial.

Figure 2

Nocturnal Trial Subjects with Baseline Nonzero Urine Volume: Time course in level of residual kidney function measured as (a) UVol; (b) Kru; or (c) Krcreat, at baseline, Month 4 and Month 12. The bar graphs depict the proportions of patients falling into the different categories and are provided to describe the outcome distribution. The bar graph ranges represent baseline tertiles (of those with nonzero function at baseline) for each variable. See Table 3 for P -values of nonparametric tests comparing the RKF parameters between treatment groups.

Figure 2

Nocturnal Trial Subjects with Baseline Nonzero Urine Volume: Time course in level of residual kidney function measured as (a) UVol; (b) Kru; or (c) Krcreat, at baseline, Month 4 and Month 12. The bar graphs depict the proportions of patients falling into the different categories and are provided to describe the outcome distribution. The bar graph ranges represent baseline tertiles (of those with nonzero function at baseline) for each variable. See Table 3 for P -values of nonparametric tests comparing the RKF parameters between treatment groups.

Figure 2

Nocturnal Trial Subjects with Baseline Nonzero Urine Volume: Time course in level of residual kidney function measured as (a) UVol; (b) Kru; or (c) Krcreat, at baseline, Month 4 and Month 12. The bar graphs depict the proportions of patients falling into the different categories and are provided to describe the outcome distribution. The bar graph ranges represent baseline tertiles (of those with nonzero function at baseline) for each variable. See Table 3 for P -values of nonparametric tests comparing the RKF parameters between treatment groups.

Figure 3

Daily Trial Subjects with Baseline Nonzero Urine Volume: Time course in level of residual kidney function measured as (a) UVol; (b) Kru; or (c) Krcreat, at baseline, Month 4 and Month 12. The bar graphs depict the proportions of patients falling into the different categories and are provided to describe the outcome distribution. The bar graph ranges represent baseline tertiles (of those with nonzero function at baseline) for each variable. See Table 4 for P -values of nonparametric tests comparing the RKF parameters between treatment groups.

Figure 3

Daily Trial Subjects with Baseline Nonzero Urine Volume: Time course in level of residual kidney function measured as (a) UVol; (b) Kru; or (c) Krcreat, at baseline, Month 4 and Month 12. The bar graphs depict the proportions of patients falling into the different categories and are provided to describe the outcome distribution. The bar graph ranges represent baseline tertiles (of those with nonzero function at baseline) for each variable. See Table 4 for P -values of nonparametric tests comparing the RKF parameters between treatment groups.

Figure 3

Daily Trial Subjects with Baseline Nonzero Urine Volume: Time course in level of residual kidney function measured as (a) UVol; (b) Kru; or (c) Krcreat, at baseline, Month 4 and Month 12. The bar graphs depict the proportions of patients falling into the different categories and are provided to describe the outcome distribution. The bar graph ranges represent baseline tertiles (of those with nonzero function at baseline) for each variable. See Table 4 for P -values of nonparametric tests comparing the RKF parameters between treatment groups.

Figure 4

Baseline and 12-month urine volumes in both trials as a function of average frequency (left panels) and average weekly dialysis times (right panels). Only those participants with nonzero urine volume at baseline were included. The solid circles represent 12-month urine volume for participants randomized to the frequent arm and open circles indicate 12-month urine volume for participants randomized to the control arm. Values of some of the points were shifted laterally slightly to reduce overlap between plot symbols. The endpoint of each vertical line linking to each circle depicts the baseline urine volume level for that particular subject.