Dialysis - Transplantation

Kidney International (1997) 52, 1395–1405; doi:10.1038/ki.1997.467

Comparison of methods to predict equilibrated Kt/V in the HEMO Pilot Study

HEMO Study Group1John T Daugirdas1, Thomas A Depner1, Frank A Gotch1, Tom Greene1, Prakash Keshaviah1, Nathan W Levin1 and Gerald Schulman1

1National Institutes of Health, NIDDK, Bethesda, Maryland

Correspondence: Gerald J Beck PhD, HEMO Study Data Coordinating Center, Department of Biostatistics and Epidemiology, P88, Cleveland Clinic Foundation, 9500 Euclid Avenue, Cleveland, Ohio 44195, USA.

1The institutions and investigators who participated in the Hemodialysis (HEMO) Pilot Study are: Garabed Eknoyan (Baylor College of Medicine), Joel Kopple (Harbor/UCLA), Andrew Levey (New England Medical Center), Nathan Levin (Beth Israel Medical Center), Gerald Schulman (Vanderbilt University Medical Center), Gerald Beck (Data Coordinating Center, Cleveland Clinic Foundation), and John Kusek, (NIDDK Project Officer).

Received 13 March 1997; Revised 2 July 1997; Accepted 3 July 1997.

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Abstract

Comparison of methods to predict equilibrated Kt/V in the HEMO Pilot Study. The ongoing HEMO Study, a National Institutes of Health (NIH) sponsored multicenter trial to test the effects of dialysis dosage and membrane flux on morbidity and mortality, was preceded by a Pilot Study (called the MMHD Pilot Study) designed to test the reliability of methods for quantifying hemodialysis. Dialysis dose was defined by the fractional urea clearance per dialysis determined by the predialysis BUN and the equilibrated postdialysis BUN after urea rebound is completed (eKt/V). In the Pilot Study the blood side standard for eKt/V was calculated from the predialysis, postdialysis, and 30-minute postdialysis BUN. Four techniques of approximating eKt/V that eliminated the requirement for the 30-minute postdialysis sample were also evaluated. The first adjusted the single compartment Kt/V using a linear equation with slope based on the relative rate of solute removal (K/V) to predict eKt/V (rate method). The second and third techniques used equations or mathematical curve fitting algorithms to fit data that included one or more samples drawn during dialysis (intradialysis methods). The fourth technique (dialysate-side) predicted eKt/V from an analysis of the time-dependent profile of dialysate urea nitrogen concentrations (BioStat method; Baxter Healthcare, Inc., Round Lake, IL, USA). The Pilot Study demonstrated the feasibility of conventional and high dose targets of about 1.0 and 1.4 for eKt/V. Based on the blood side standard method, the mean plusminus SD eKt/V for patients randomized to these targets was 1.14 plusminus 0.11 and 1.52 plusminus 0.15 (N = 19 and 16 patients, respectively). Single-pool Kt/Vs were about 0.2 Kt/V units higher. Results were similar when eKt/V was based on dialysate side measurements: 1.10 plusminus 0.11 and 1.50 plusminus 0.11. The approximations of eKt/V by the three blood side methods that eliminated the delayed 30-minute post-dialysis sample correlated well with eKt/V from the standard blood side method: r = 0.78 and 0.76 for the single-sample (Smye) and multiple-sample intradialysis methods (N = 295 and 229 sessions, respectively) and 0.85 for the rate method (N = 295). The median absolute difference between eKt/V computed using the standard blood side method and eKt/V from the four other methods ranged from 0.064 to 0.097, with the smallest difference (and hence best accuracy) for the rate method. The results suggest that, in a dialysis patient population selected for ability to achieve an equilibrated Kt/V of about 1.45 in less than a 4.5 hour period, use of the pre and postdialysis samples and a kinetically derived rate equation gives reasonably good prediction of equilibrated Kt/V. Addition of one or more intradialytic samples does not appear to increase accuracy of predicting the equilibrated Kt/V in the majority of patients. A method based on dialysate urea analysis and curve-fitting yields results for equilibrated Kt/V that are similar to those obtained using exclusively blood-based techniques of kinetic modeling.

Keywords:

urea kinetics, pharmacokinetics, hemodialysis, modeling, rebound, clearance, organ blood flow

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