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      Urea Reduction Ratio Considering Urea Rebound

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          An American National Study shows that survival benefits from higher dialysis doses appear to be present up to a Kt/V level of 1.3 or a urea reduction ratio (URR) of 70%. The effect of increasing dialysis efficiency magnified urea rebound and the error in URR determinations. Several formulas have been developed to calculate URR considering the urea rebound (URRr). Smye and coworkers have proposed a method whereby the equilibrated blood urea nitrogen is predicted by additional intradialytic urea sample. Maduell and colleagues, based on analysis of postdialysis urea rebound, have proposed a method whereby the urea rebound is predicted. To compare measured URRr to estimated by Smye and Maduell formulas, 384 patients were studied, 211 males and 173 females, who received a dialysis session with their habitual parameters. Measurements of plasma urea concentration were obtained at the beginning, 90–100 min following the start of dialysis, at the end, and 45 min after dialysis. The postdialysis urea rebound was 22.4 ± 9.7%. The urea kinetic model Kt/V was 1.365 ± 0.26, and Kt/Vr was 1.14 ± 0.23. URR was 68.7 ± 6.6%, and when it was calculated with urea rebound, it decreased to 61.9 ± 7.4%. The URRr correlated with calculations by Smye and Maduell formulas: 60.7 ± 8.4 (r = 0.722, p < 0.001) and 61.8 ± 6.6 (r = 0.933, p < 0.001), respectively. The precision of estimated limits of agreement and percentage of error by Bland and Altman analysis show that URRr estimated Maduell formula could be used in place of the URRr. Otherwise, the degree of agreement of the Smye method was not clinically acceptable. In conclusion, our results led us to suggest that in actual dialysis, the use of URR is not adequate for delivered hemodialysis dose, and URRr should be used. URRr estimated by Maduell formula could be a simple and accurate method for use in clinical practice. The recommended dialysis dose by the American National Study of URR of 70% could correspond, considering urea rebound, to Kt/Vr 1.18 or URRr of 64%.

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          The urea reduction ratio and serum albumin concentration as predictors of mortality in patients undergoing hemodialysis.

          Among patients with end-stage renal disease who are treated with hemodialysis, solute clearance during dialysis and nutritional adequacy are determinants of mortality. We determined the effects of reductions in blood urea nitrogen concentrations during dialysis and changes in serum albumin concentrations, as an indicator of nutritional status, on mortality in a large group of patients treated with hemodialysis. We analyzed retrospectively the demographic characteristics, mortality rate, duration of hemodialysis, serum albumin concentration, and urea reduction ratio (defined as the percent reduction in blood urea nitrogen concentration during a single dialysis treatment) in 13,473 patients treated from October 1, 1990, through March 31, 1991. The risk of death was determined as a function of the urea reduction ratio and serum albumin concentration. As compared with patients with urea reduction ratios of 65 to 69 percent, patients with values below 60 percent had a higher risk of death during follow-up (odds ratio, 1.28 for urea reduction ratios of 55 to 59 percent and 1.39 for ratios below 55 percent). Fifty-five percent of the patients had urea reduction ratios below 60 percent. The duration of dialysis was not predictive of mortality. The serum albumin concentration was a more powerful (21 times greater) predictor of death than the urea reduction ratio, and 60 percent of the patients had serum albumin concentrations predictive of an increased risk of death (values below 4.0 g per deciliter). The odds ratio for death was 1.48 for serum albumin concentrations of 3.5 to 3.9 g per deciliter and 3.13 for concentrations of 3.0 to 3.4 g per deciliter. Diabetic patients had lower serum albumin concentrations and urea reduction ratios than nondiabetic patients. Low urea reduction ratios during dialysis are associated with increased odds ratios for death. These risks are worsened by inadequate nutrition.
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            Paediatric haemodialysis: estimation of treatment efficiency in the presence of urea rebound

             S. W. Smye,  J. EVANS,  E Will (1992)

              Author and article information

              S. Karger AG
              February 1998
              26 January 1998
              : 78
              : 2
              : 143-147
              Nephrology Departments, a Hospital General de Castellón, b Hospital Clínico de Granada, c Hospital de Gandia, d Hospital de Xàtiva, e Hospital de Alcoy, f Hemogan, Gandia, g Hospital General de Valencia, h Cedicas, Castellón, Spain
              44902 Nephron 1998;78:143–147
              © 1998 S. Karger AG, Basel

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              Page count
              Figures: 2, Tables: 1, References: 21, Pages: 5
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              Original Paper

              Cardiovascular Medicine, Nephrology

              Urea reduction ratio, Hemodialysis dose, Urea rebound


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