Dialysis – Transplantation
Kidney International (2004) 66, 1669–1676; doi:10.1111/j.1523-1755.2004.00934.x
Kinetics of urea and 
2-microglobulin during and after short hemodialysis treatments
JOHN K LEYPOLDT, ALFRED K CHEUNG, R BARRY DEETER, ALEXANDER GOLDFARB-RUMYANTZEV, TOM GREENE, THOMAS A DEPNER and JOHN KUSEK
VA Salt Lake City Health Care System, Salt Lake City, Utah; University of Utah, Salt Lake City, Utah; Cleveland Clinic Foundation, Cleveland, Ohio; University of California, Davis, Sacramento, California; National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, Maryland
Correspondence: John (Ken) Leypoldt, Ph.D., Dialysis Program, University of Utah, 85 N. Medical Drive East Room 201, Salt Lake City, UT 84112-5350. E-mail: Ken.Leypoldt@hsc.utah.edu
Received 23 September 2003; Revised 26 April 2004; Accepted 11 May 2004.
Abstract
Kinetics of urea and 
2-microglobulin during and after short hemodialysis treatments.
Background
Daily short hemodialysis (HD) is often prescribed by simply doubling treatment frequency and halving treatment time; however, the effect of this prescription approach on the equilibrated HD dose (urea eKt/V) and whole body clearance for 
2-microglobulin has not been established.
Methods
We compared urea and 2-microglobulin kinetics during and 60 minutes after a short HD treatment and a conventional HD treatment in a crossover study on 22 maintenance HD patients: 16 male and 6 female, 61 
18 (mean standard deviation) years of age. One patient in each treatment modality was excluded from certain analyses because of missing data. Short and conventional HD treatments were essentially identical, except for treatment times, which were 116 14 and 241 27 minutes, respectively. Blood samples were collected at regular intervals during and after treatments, and additional blood and dialysate samples were collected at 60 minutes of treatment to evaluate dialyzer clearances.
Results
Plasma water urea clearances measured directly across the dialyzer during short and conventional HD treatments were not different (255 23 mL/min and 255 28 mL/min, respectively). The 60-minute postdialysis blood urea nitrogen concentration rebounded more (P < 0.01) after short HD than conventional HD (5.9 3.1 vs. 4.0 1.5 mg/dL, respectively). Calculated urea eKt/V values using the Daugirdas-Schneditz rate equation were not different from those measured during conventional HD using the 60-minute postdialysis concentration but significantly overestimated measured urea eKt/V values during short HD. Postdialysis rebound of 2-microglobulin concentrations was variable but similar after short and conventional HD treatments (0.1 3.4 vs. 0.7 1.8 mg/L, respectively). Whole body clearances of 2-microglobulin calculated from predialysis and immediate (10-second) postdialysis serum concentrations during short and conventional HD treatments were not different from each other (42.9 24.1 vs. 41.9 22.4 mL/min, respectively).
Conclusion
These observations show that the Daugirdas-Schneditz rate equation is accurate in predicting urea eKt/V during conventional, but not during short, HD. In contrast, whole body clearances of 2-microglobulin during short and conventional HD treatments were similar. We conclude that calculation of accurate estimates of urea eKt/V, but not clearances of 2-microglobulin, differ during short and conventional HD treatments.
Keywords:
adequacy, clearance, dose, middle molecule, postdialysis rebound
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