Incremental Hemodialysis, Residual Kidney Function, and Mortality Risk in Incident Dialysis Patients: A Cohort Study

Abstract

Background: Maintenance hemodialysis is typically prescribed thrice weekly irrespective of a patient's residual kidney function (RKF). We hypothesized that a less frequent schedule at hemodialysis therapy initiation is associated with greater preservation of RKF without compromising survival among patients with substantial RKF.

Study design: A longitudinal cohort.

Setting & participants: 23,645 patients who initiated maintenance hemodialysis therapy in a large dialysis organization in the United States (January 2007 to December 2010), had available RKF data during the first 91 days (or quarter) of dialysis, and survived the first year.

Predictor: Incremental (routine twice weekly for >6 continuous weeks during the first 91 days upon transition to dialysis) versus conventional (thrice weekly) hemodialysis regimens during the same time.

Outcomes: Changes in renal urea clearance and urine volume during 1 year after the first quarter and survival after the first year.

Results: Among 23,645 included patients, 51% had substantial renal urea clearance (≥3.0mL/min/1.73m(2)) at baseline. Compared with 8,068 patients with conventional hemodialysis regimens matched based on baseline renal urea clearance, urine volume, age, sex, diabetes, and central venous catheter use, 351 patients with incremental regimens exhibited 16% (95% CI, 5%-28%) and 15% (95% CI, 2%-30%) more preserved renal urea clearance and urine volume at the second quarter, respectively, which persisted across the following quarters. Incremental regimens showed higher mortality risk in patients with inadequate baseline renal urea clearance (≤3.0mL/min/1.73m(2); HR, 1.61; 95% CI, 1.07-2.44), but not in those with higher baseline renal urea clearance (HR, 0.99; 95% CI, 0.76-1.28). Results were similar in a subgroup defined by baseline urine volume of 600mL/d.

Limitations: Potential selection bias and wide CIs.

Conclusions: Among incident hemodialysis patients with substantial RKF, incremental hemodialysis may be a safe treatment regimen and is associated with greater preservation of RKF, whereas higher mortality is observed after the first year of dialysis in those with the lowest RKF. Clinical trials are needed to examine the safety and effectiveness of twice-weekly hemodialysis.

Keywords: Incremental hemodialysis; dialysis initiation; frequent hemodialysis; interdialytic weight gain; mortality; renal urea clearance; residual kidney function (RKF); standard Kt/V; treatment regimen; twice-weekly hemodialysis.

Figure 1

Achievement rate of the minimum total standard Kt/V >2.1 among patients with the incremental and conventional hemodialysis, stratified by renal urea clearance (KRU). Abbreviation: HD, hemodialysis.

Figure 2

Trends over time of the mean and the relative ratio of residual kidney function in the matched cohort of 8,419 patients across five patient-quarters (PQ) (the conventional vs. incremental hemodialysis regimen). Analyses of renal urea clearance (KRU) and urine volume (UV) are shown in Panels A and C, and B and D, respectively. Data are based on weighted match according to baseline KRU and UV as well as age, gender, race, central venous catheter as vascular access, and history of diabetes. Points and error bars represent point estimates and 95% confidence intervals, respectively. Abbreviation: HD, hemodialysis.

Figure 3

Kaplan-Meier survival curve and confidence intervals for all-cause death after Year 1 in the matched cohort of 8,419 patients. Abbreviation: HD, hemodialysis.

Figure 4

Over all and subgroup analyses of the association of the incremental regimen (vs. the conventional regimen) with all-cause mortality in the matched cohort of 8,419 patients. Points and error bars represent point estimates and 95% confidence intervals, respectively. Abbreviations: KRU, residual renal urea clearance; IDWG, inter-dialytic weight gain; HD, hemodialysis.

Figure 5

Casemix-adjusted mortality risk of the incremental hemodialysis regimen among patients with in the entire cohort stratified by baseline renal urea clearance (KRU), urine volume, or weekly interdialytic weight gain (IDWG) across the survival periods of 3 months, 6months, 9 months, and 12 months. Points and error bars represent point estimates and 95% confidence intervals, respectively