INFLUENCE OF DIALYZER CLEARANCE MEASUREMENT ACCURACY ON HEMODIALYSIS PRESCRIPTION BASED ON KT V/

Kt/V urea (u) has been used as a measure of adequacy of haemodialysis (HD). However, the accurate assessment of its components is difficult and subject to error in a clinical setting. This study was designed to evaluate different forms of dialyser clearance (K) measurements and t heir influence on Kt/V Sixteen patients on high-flux HD were studied a t blood flow (Q(b)) rates of 250 and 350 ml/min and at constant dialys ate flow rates. K of urea was measured by the arteriovenous blood samp ling technique (K(bu)), corrected for access recirculation (K(bru)) an d compared with K as determined by dialysate collection (K(du)) using a new sampling device. At Q(b) 250 and 350 ml/min, K(bu) as based on d ialysate collection was significantly lower than K(bru) and K(bu) as b ased on arteriovenous blood sampling: at Q(b) 250, K(du) 169.0 +/- 13. 3, K(bru) 191.2 +/- 11.5, and K(bu) 203.0 +/- 9.3 ml/min (P < 0.0005); at Q(b) 350, K(du) 196.5 +/- 17.3, K(bru) 227.7 +/- 15.5, and K(bu) 2 43.6 +/-12.7 ml/min (P < 0.0005). At Q(b) 250 ml/min K(bu) t/v (1.33 /- 0.17) overestimated K(du) t/V (1.11 +/- 0.13) by 16.8%, at Q(b) 350 ml/min by 19.3% (1.58 +/- 0.19 versus 1.27 +/- 0.15). Dialyser cleara nces based on arteriovenous differences in blood overestimate true cle arances (and therefore Kt/V) as measured by dialysate collection. This overestimation is more marked with higher blood flow rates.