The relationship between the delivered dose of hemodialysis and patient mortality
remains somewhat controversial. Several observational studies have shown improved
patient survival with higher levels of delivered dialysis dose. However, several other
unmeasured variables, changes in patient mix or medical management may have impacted
on this reported difference in mortality. The current study of a U.S. national sample
of 2,311 patients from 347 dialysis units estimates the relationship of delivered
hemodialysis dose to mortality, with a statistical adjustment for an extensive list
of comorbidity/risk factors. Additionally this study investigated the existence of
a dose beyond which more dialysis does not appear to lower mortality. We estimated
patient survival using proportional hazards regression techniques, adjusting for 21
patient comorbidity/risk factors with stratification for nine Census regions. The
patient sample was 2,311 Medicare hemodialysis patients treated with bicarbonate dialysate
as of 12/31/90 who had end-stage renal disease for at least one year. Patient follow-up
ranged between 1.5 and 2.4 years. The measurement of delivered therapy was based on
two alternative measures of intradialytic urea reduction, the urea reduction ratio
(URR) and Kt/V (with adjustment for urea generation and ultrafiltration). Hemodialysis
patient mortality showed a strong and robust inverse correlation with delivered hemodialysis
dose whether measured by Kt/V or by URR. Mortality risk was lower by 7% (P = 0.001)
with each 0.1 higher level of delivered Kt/V. (Expressed in terms of URR, mortality
was lower by 11% with each 5 percentage point higher URR; P = 0.001). Above a URR
of 70% or a Kt/V of 1.3 these data did not provide statistical evidence of further
reductions in mortality. In conclusion, the delivered dose of hemodialysis therapy
is an important predictor of patient mortality. In a population of dialysis patients
with a very high mortality rate, it appears that increasing the level of delivered
therapy offers a practical and efficient means of lowering the mortality rate. The
level of hemodialysis dose measured by URR or Kt/V beyond which the mortality rate
does not continue to decrease, though not well defined with this study, appears to
be above current levels of typical treatment of hemodialysis patients in the U.S.