Determinants of prescribed dialysis dose and survival in a cohort of chronic hemodialysis patients

Abstract

Background: The Determinants of the prescribed dialysis dose have not been well studied in a large patient population. Few studies have examined survival rates after adjusting for dose determinants.

Methods: Data were obtained from a cohort of chronic hemodialysis patients for the period January 1991 through December 2000. The prescribed dialysis dose was calculated as the dialyzer membrane area (m2) times session hours, and was expressed as m2h per week. Determinants of the prescribed dialysis dose were examined by multivariate logistic regression analysis of baseline clinical and laboratory variables. Survival curves for each prescribed dose were calculated by the Kaplan-Meier method. Cox proportional hazards analysis was used to evaluate differences in the survival curves after adjusting for confounding variables. The delivered dose of dialysis, Kt/V, was calculated in a subgroup of the cohort.

Results: For 1041 patients receiving thrice-weekly dialysis, the mean (SD) dialysis dose was 19.8 (5.8) m2h/week (range, 6.3 to 33.0 m2h/week). The significant and independent determinants of prescribed dialysis dose were sex, age, diabetes mellitus (DM), body mass index (BMI), serum albumin, diastolic blood pressure, serum creatinine, duration of dialysis, and comorbidity. The dialysis dose received by women and patients with DM was relatively low, even when adjusted for BMI ( P < 0.01 for both). During the follow-up period, 463 patients died, 60 underwent renal transplant, and 10 were transferred away from Okinawa. The hazard ratio (95% confidence interval) for death was 1.016 (0.995-1.037; not significant) for the dialysis dose (m2h/week) after adjustment for multiple confounding factors. The mean (SD) Kt/V was 1.31 (0.28). The hazard ratio (95% confidence interval) for Kt/V > or = 1.31 vs Kt/V < or = 1.30 was 0.706 (0.553-0.900; P = 0.0049).

Conclusions: The prescribed dialysis dose did not significantly influence mortality in our cohort. Empirically based prescription practice, such as increasing the prescribed dialysis dose in male patients, when the BMI is large, or when serum creatinine or diastolic blood pressure is high may explain the relatively good prognosis of chronic hemodialysis patients in Japan.