How can we tell if we are delivering good dialysis?

This blog post was made by Dr. John Agar on November 13, 2013.
How can we tell if we are delivering good dialysis?

When it comes to assessing what is 'good dialysis', what should we take cognizance of?

Should we embrace Kt/V? Or URR (PRU)? Or just Kt? Or, with apologies to William Shakespeare, should we decide "a pox on all their houses" and simply embrace a Scribner and Oreopoulos gem – the haemodialysis product (HDP)1...a gem far too few have ever read or considered: treatment x frequency squared (t x f2).

Of all the choices, the latter does it for me. While I do see some transitional justification in abandoning V and using Kt alone, perhaps with the inclusion of surface area normalization (SAN), modern biocompatible membranes, high efficiency and reliable equipment, commercially batched dialysates, and established dialysis protocols should turn us back, now, to examine the only two things that really matter – longer time and higher frequency dialysis.

It is past time that we collectively agreed that Kt/V simply doesn't cut the mustard, no matter which contortion of the concept one adopts. These contortions (or distortions) emerged as Kt/V was found wanting, yet as each has trended to a greater mathematical complexity than the last, we have simply been digging the same hole...deeper and deeper. Convoluted mathematical discourse supporting or debunking Kt/V, spKt/V, eKt/V, stdKt/V, SAN-spKt/V, SAN-eKt/V, SAN-stdKt/V have attempted to further modify an equation that, arguably, should never ever have been applied to dialysis in the first place. But, apply it we did, while some—and here I direct particular opprobrium to the US—accorded it the imprimatur of a national Key Performance Indicator.

My patient, as he (or she) sits beside me in 'that chair', umbilically attached to a big beige or blue machine, is not an equation. He (or she) is not a maze of multiplications, divisions, logarithms, constants, and powers to the 'n'. He (or she) is my patient, a person just like me, and what right do I have to reduce that sinew and muscle, mind and emotion, thinking, loving amalgam of hope, pain and despair to a mathematical equation? I contend, none!

While all that matters to my patient is "how long" and "how often," two questions that rise above all others, we have again chosen a diametrically opposite direction. Rather than explaining and persuading for longer and more frequent treatments, and exploring the best ways to make those goals more palatable for our patients, we have chosen to shorten and brutalize dialysis, not lengthen and 'subliminalize' it. We have sought to test the limits of biochemical and volume change—like some bizarre reality TV show that seeks to test the limits a human body can withstand before it collapses. Why construct a TV set? Just film a dialysis session!

Mathematical dialysis makes no sense. Humanized dialysis should. We should seek a haemodialysis model that espouses three key factors: dialysis at home, dialysis during sleep, dialysis while mobile.

PD embodies all these—and PD patients don't keel over! Why not? Because PD is continuous, slow, and gentle. PD mobilises deep tissue solutes through muscular activity (it's called walking), but, while PD should clearly be markedly up-valued, it is not for all, nor is it forever.

Meanwhile, HD patients—the silent majority—remain chair bound. But, why? Because we "go at them" so hard, so fast, so Kt/V-driven, that if they were to stand, their sucked-dry circulations would collapse. The Kt/V mantra? "Get 'em all to their 'required' Kt/V as fast as possible, then stop their treatment and welcome the next victims in." The faster you can get 'em "there," the shorter their treatment time will be. And, when profit is brought to the mix, a mathematical solution seems even more compelling.

HD can be, should be, must be delivered by much longer and gentler paradigms. Scrib and Dimitri knew this when they proposed t x f2 as the only measure of dialysis that matters. Lengthen 't', they wrote. Even more, increase 'f'. They squared it—as their only math.

It can be done, and done successfully in almost all patients. Take a moment to look at the Christchurch and Dunedin model in New Zealand if you remain uncertain.

If they can, why not others?


  • Scribner BH, Oreopoulos DG. The Hemodialysis Product (HDP): A better index of dialysis adequacy than Kt/V. Dialysis and Transplantation, 2002 40 (10: 431- 433.
    Also found at:


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