The Hemodialysis Product (HDP): A Better Index of Dialysis Adequacy than Kt/V {January 2002}

n a recent issue of this journal, Dr. Peter Blake and others commented on the ADEMEX (Adequacy of Peritoneal Dialysis in Mexico) study, a brilliantly planned and conducted study on the influence of increases in Kt/V on the outcome of anuric continuous ambulatory peritoneal dialysis (CAPD) patients in Mexico. This prospective, controlled study was presented at the recent meeting of the International Society for Peritoneal Dialysis (Montreal, June 2001), but has not yet been published. The results were clear-cut and highly significant. Specifically, they demonstrated that increasing the dose of CAPD—as measured by Kt/V and weekly creatinine clearance— among anuric CAPD patients had no effect on patient survival when compared to a control group on a lower dose of dialysis. This result provides additional evidence that Kt/V is a flawed concept upon which to base the dose of dialysis in general. The prime example that Kt/V is flawed is that it fosters short hemodialysis, which is inefficient in removing toxic middle molecules. Short hemodialysis may give a false impression of highly efficient hemodialysis by removing fast-diffusing urea and, thus, resulting in a high Kt/V. However, removal of toxic middle molecules and PO4, which dialyzes like a middle molecule, is reduced because of the shortened time. Short hemodialysis sessions have great appeal only to the uninformed dialysis patient and to for-profit dialysis centers. For the last three decades worldwide, but especially in the U.S.A., belief among the hemodialysis community in the reliability of Kt/V, combined with the natural desire of the patient to have the shortest possible time on dialysis, has resulted in the underdialysis of the vast majority of hemodialysis patients.