COMPARISON OF METHODS TO PREDICT EQUILIBRATED KT V IN THE HEMO PILOT-STUDY/

The ongoing HEMO Study, a National Institutes of Health (NIH) sponsore d multicenter trial to test the effects of dialysis dosage and membran e flux on morbidity and mortality, was preceded by a Pilot Study (call ed the MMHD Pilot Study) designed to test the reliability of methods f or quantifying hemodialysis. Dialysis dose was defined by the fraction al urea clearance per dialysis determined by the predialysis BUN and t he equilibrated postdialysis BUN after urea rebound is completed (eKt/ V). In the Pilot Study the blood side standard for eKt/V was calculate d 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 slop e based on the relative rate of solute removal (K/V) to predict eKt/V (rate method). The second and third techniques used equations or mathe matical curve fitting algorithms to fit data that included one or more samples drawn during dialysis (intradialysis methods). The fourth tec hnique (dialysate-side) predicted eKt/V from an analysis of the time-d ependent profile of dialysate urea nitrogen concentrations (BioStat me thod; Baxter Healthcare, Inc., Round Lake, IL, USA). The Pilot Study d emonstrated the feasibility of conventional and high dose targets of a bout 1.0 and 1.4 far eKt/V. Based on the blood side standard method, t he mean +/- SD eKt/V for patients randomized to these targets was 1.14 +/- 0.11 and 1.52 +/- 0.15 (N = 19 and 16 patients, respectively). Si ngle-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 +/- 0.11 an d 1.50 +/- 0.11. The approximations of eKt/V by the three blood side m ethods that eliminated the delayed 30-minute post-dialysis sample corr elated well with eKt/V from the standard blood side method: r = 0.78 a nd 0.76 for the single-sample (Smye) and multiple-sample intradialysis methods (N = 295 and 229 sessions, respectively) and 0.85 for the rat e method (N = 295). The median absolute difference between eKt/V compu ted 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, i n a dialysis patient population selected for ability to achieve an equ ilibrated Kt/V of about 1.45 in less than a 4.5 hour period, use of th e pre and postdialysis samples and a kinetically derived rate equation gives reasonably good prediction of equilibrated Kt/V. Addition of on e or more intradialytic samples does not appear to increase accuracy o f predicting the equilibrated Kt/V in the majority of patients. A meth od based on dialysate urea analysis and curve-fitting yields results f or equilibrated Kt/V that are similar to those obtained using exclusiv ely blood-based techniques of kinetic modelling.