Role of residual renal function in phosphate control and anemia management in chronic hemodialysis patients

Abstract

Background and objectives: There is increasing awareness that residual renal function (RRF) has beneficial effects in hemodialysis (HD) patients. The aim of this study was to investigate the role of RRF, expressed as GFR, in phosphate and anemia management in chronic HD patients.

Design, setting, participants, & measurements: Baseline data of 552 consecutive patients from the Convective Transport Study (CONTRAST) were analyzed. Patients with a urinary output≥100 ml/24 h (n=295) were categorized in tertiles on the basis of degree of GFR and compared with anuric patients (i.e., urinary output<100 ml/24 h, n=274). Relations between GFR and serum phosphate and erythropoiesis-stimulating agent (ESA) index (weekly ESA dose per kg body weight divided by hematocrit) were analyzed with multivariable regression models.

Results: Phosphate levels were between 3.5 and 5.5 mg/dl in 68% of patients in the upper tertile (GFR>4.13 ml/min per 1.73 m2), as compared with 46% in anuric patients despite lower prescription of phosphate-binding agents. Mean hemoglobin levels were 11.9±1.2 g/dl with no differences between the GFR categories. The ESA index was 31% lower in patients in the upper tertile as compared with anuric patients. After adjustments for patient characteristics, patients in the upper tertile had significantly lower serum phosphate levels and ESA index as compared with anuric patients.

Conclusions: This study suggests a strong relation between RRF and improved phosphate and anemia control in HD patients. Efforts to preserve RRF in HD patients could improve outcomes and should be encouraged.

Trial registration: ClinicalTrials.gov NCT00205556.

Figure 1.

Percentage of patients below, within, or above phosphate treatment targets by GFR category.

Figure 2.

Relationship between RRF and use of phosphate-binding agents. Each box shows the distribution of phosphate-binding agent use in DDD for the range of RRF as indicated on the horizontal axis. The mean dose is shown by the black circle, the median by the middle horizontal line, and the 25th and 75th percentiles by the bottom and top of the box, respectively. P for univariable linear trend = 0.008.

Figure 3.

Relationship between residual renal function and ESA index. Each box shows the distribution of ESA index, defined as the ESA dose per week (in DDD) per kilogram of body weight per percent hematocrit, for the range of RRF as indicated on the horizontal axis. The mean dose for each group is shown by the black circles, the median by the middle horizontal line, and the 25th and 75th percentiles by the bottom and top of the box, respectively. P for univariable linear trend = 0.001.