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Ultrafiltration Rate, Residual Kidney Function, and Survival Among Patients Treated with Reduced-frequency Hemodialysis

American Journal of Kidney Disease. 75(3): 342-350

Recently, clinical application of less-frequent hemodialysis (HD), such as twice-weekly HD, has increased in consideration of the potential benefits including higher health-related quality of life, better preservation of residual kidney function, reduced risk related to the dialysis procedure, and comparable survival rates compared with thrice-weekly hemodialysis. However, patients receiving less-frequent HD may need to undergo higher ultrafiltration rates (UFRs) to maintain acceptable fluid balance, which may lead to increased mortality. Hence, we investigated that higher UFRs are associated with faster decline in residual kidney function (RKF) and a higher rate of mortality.

We performed a retrospective cohort study using a cohort of adult patients with kidney failure who initiated maintenance HD at a frequency of twice or less per week for at least 6 consecutive weeks at some time between 2007 and 2011 and for whom baseline data for UFR and renal urea clearance was available. The exposure of interest was average UFR during the first less-frequent HD patient-quarter (<6, 6-10, 10-<13, and ≥13 mL/h/kg). The primary outcomes were all-cause and cardiovascular mortality. The secondary outcome was a slope of decline in RKF during the first year after initiation of less- frequent HD (with slopes above the median categorized as rapid decline).

Among 1,524 patients, higher UFR was associated with higher all-cause mortality; hazard ratios (HRs) were 1.43 (95% CI, 1.09–1.88), 1.51 (95% CI, 1.08–2.10), and 1.76 (95% CI, 1.23–2.53) for UFR of 6 to <10, 10 to <13, and ≥13 mL/h/kg, respectively (reference: UFR <6 mL/h/kg). Higher UFR was also associated with higher cardiovascular mortality. Baseline RKF modified the association between UFR and mortality; the association was attenuated among patients with renal urea clearance ≥5 mL/min/1.73m2 (P for interaction = 0.005) (Fig. 1). Higher UFR had a graded association with rapid decline in RKF; odds ratios were 1.73 (95% CI, 1.18–2.55), 1.89 (95% CI, 1.12–3.17), and 2.75 (95% CI, 1.46–5.18) at UFRs of 6 to <10, 10 to <13, and ≥13 mL/h/kg, respectively (reference: UFR <6 mL/h/kg).

In conclusion, the results of the current study indicate that higher UFR is associated with worse outcomes, including shorter survival and more rapid loss of RKF, among patients receiving regular HD treatments at a frequency of twice or less per week.