Dialysis: a Duopoly of Solutes and Volume—Not a Solute Monopoly Alone

This blog post was made by Dori Schatell, MS, Executive Director, Medical Education Institute on September 3, 2015.
Dialysis: a Duopoly of Solutes <em>and</em> Volume—Not a Solute Monopoly Alone

co-authored by Dori Schatell and Dr. John Agar

A couple of weeks ago, I was honored to have a chance to present on a webinar with Dr. Paul Miller, organized by the CMS Clinical Standards and Quality (CCSQ) group, which sets the quality parameters for US dialysis, along with other beneficiary care. Our topic was dialysis volume as a safety issue, with an audience of ESRD Network Executive Directors, Medical Directors, and Quality Directors. For a couple of weeks longer (don’t wait!) you can download the presentation and Webex player for it here.

Astoundingly, the USRDS does not include data on the speed of water removal during dialysis, or ultrafiltration rate (UFR). The word “ultrafiltration” does not even appear in the Annual Data Report! Until now, we have actually been ignoring one of the most important numbers we have to guide safe and effective HD treatments. So, it is very exciting to see CMS start to devote some attention to the vital issue of UFR in dialysis and how to optimize care, starting with measuring this critical parameter. The 2016 proposed QIP measures include a target UFR of 13 mL/Hr/Kg, which MEI, in our public comment, suggested changing to 10 mL/Hr/Kg.

My Australian nephrologist collaborator and partner in crime, John Agar, has long had much to say about this forgotten issue, and taught me much of what I know. For more than a decade, he has:

  1. Warned of the dangers of rapid fluid removal, especially as it is commonly practiced in the U.S. The mean dialysis session time in the US (also not collected for the USRDS!) is among the shortest in the world, and the mean UFR is among the most rapid.
  2. Proselytized the need to measure UFR, not only here, but also in his most recent paper in Hemodialysis International(1) and in many answers to patient questions at his message board Q&A site on Home Dialysis Central.

When I told him about my CCSQ interaction, he sent me a ‘Volume 101’ email that gathered key volume dot-points that he would have wanted to make clear. With his permission, I am sharing it below, for those of you who didn’t get a chance to attend that webinar.

Dear Dori,

What follows is a synthesis of the dot points I would want to cover at any meeting you might have with those in the US who might really care about improving the poor dialysis outcomes you have over there. By all sensible criteria, you should be ahead of the game, not—as you are—bringing up the international rear by a number of trailing laps.

Key dot points:

  • The kidneys are one of our “vital organs.”
  • If the kidneys fail, death results.
  • To prevent death, we have dialysis and/or transplantation.
  • Transplantation, the best option, is unfortunately impractical for many as a result of advancing age, co-morbidity, sensitisation, unavailability, or combinations of these.
  • Thus, waiting-time or permanent dialysis is the only option for the majority.
  • But, if applied inefficiently, or for an inadequate duration or frequency, dialysis kills, too.
  • Dialysis kills in two ways: through solute or electrolyte imbalance, or through fluid overload.
  • Of these, solute and electrolyte accumulation has always been of lesser outcome impact, yet it has always received the lion’s share of attention.
  • Over time, better membranes, smarter technology, dietary management, and keener understanding have all combined to largely eliminate the risk of “death by solute”—not that it ever was the greatest enemy of the dialysis patient.
  • The real enemy has always been “volume.”
  • Despite its lesser impact, death by solute has largely been defeated by the introduction of a solute Key Performance Indicator (KPI)—in the US, Kt/V, or commonly elsewhere, the PRU – two similar measures of solute “adequacy” that are now regularly monitored and widely achieved. Kt/V has served a purpose: (2) it has set an achievable minimum to protect against “death by solute,” and, for that, we should rightly acknowledge its role.
  • “Death by volume”—always the more prevalent and insidious killer—remains unconquered. Volume is the elephant in the dialysis room.
  • Volume overload leads to death by drowning, while the brutal rate of volume removal that accompanies rapid dialysis leads to death by organ and tissue stun—functional tissue or organ ischaemia induced by hypo-perfusion (diminished blood flow) and hypo-oxygenation (diminished oxygen delivery).
  • In my view, there is little doubt that a volume KPI would have a far greater outcome impact than ever the current solute KPI’s have had.
  • So…I made a personal decision to try to lead the elephant into the light! (1)

What we know:

  • We know pre-dialysis weight—always.
  • We know post-dialysis target weight—we set this for every dialysis.  NOTE: this is not necessarily “dry weight,” but is the weight we aim to reach by the end of a run. These are not always the same thing.
  • We know that removing fluid at >10 ml/kg/hr risks a rapid escalation in morbidity and mortality:
Associations between UFR and CV and all-cause mortality
From Flythe et al:
Kidney International (2011) 79, 250–257; doi:10.1038/ki.2010.383; 6 October 2010
  • If we know these, then we also know how long any one treatment should last to ensure that the rate of fluid removal remains, for each and every treatment, at <10 ml/kg/hr.

What should we conclude:

  • Dialysis duration should be the key variable in all and every dialysis program.
  • Dialysis should last long enough to ensure that the solute KPI (a Kt/V of 1.3, or a PRU >70%) is achieved.
  • But dialysis must also last long enough to ensure that a volume KPI of <10 ml/kg/hr is achieved.
  • To shoot for one, but not the other, abrogates our duty of care to our patients.
  • Both matter, and both must be achieved.


So, Dori, these are the simple, bare-arsed truths that our decision-makers—often administrators without medical training—need to understand, in addition to:

  • While dialysis has been a solute monopoly, in truth, it is a duopoly, and solutes play the lesser part.
  • Volume must be better understood. It must be recognised, quantified, and corralled.
  • We will never achieve optimal dialysis by calling our patients non-compliant when, after rapid and excessive volume contraction by aggressive, fast dialysis, they crawl home, their thirst centres fully activated by volume depletion, desperate to drink and regain all that fluid—and more—before the next treatment. Draconian fluid restriction has never worked, and is rarely enforceable.
  • This is not rocket science, yet, oddly, this simplest of dilemmas is poorly understood! Indeed, while volume control is a far easier, simpler and more concrete concept to grasp than the nebulous, notional concept of Kt/V, it is Kt/V that has ruled our roost, while the volume argument has been relegated to a “compliance issue.”
  • As programs are forced to change practise patterns and deliver more time (durational) flexibility in their programs, there will be the kickers and screamers. So be it. The dust will settle!
  • But, in the end, the dialysis will be a far more humane, far more effective, and far less murderous process than it is under current practices. And, this can only be a good thing!



  1.  Agar JWM. Personal Viewpoint: Limiting maximum ultrafiltration rate as a potential new measure of dialysis adequacy. Hemodialysis International. Published as a ‘early view’ doi at: http://authorservices.wiley.com/bauthor/onlineLibraryTPS.asp?DOI=10.1111/hdi.12288&ArticleID=2602771
  2. Agar JWM, Schatell D. Kt/V has served its’ purpose, so let us now move on. Nephrology News and Issues (on-line edition). To be found at: http://www.nephrologynews.com/ktvurea-has-served-its-purpose-so-let-us-now-move-on/

So, I did try to channel John, and use what he’s taught me to share key messages with the webinar audience, but thought you might appreciate a chance to see his full-on chain of logic. I’ll be keeping an eye out to see if the proposed QIP measure for UFR of 13 mL/Hr/Kg becomes a real measure, and if so, if there is a potential to shift it to where it should be for safety: 10mL/Hr/Kg. If I needed dialysis, I wouldn’t want a UFR over 10—and you wouldn’t, either.


  • Diane Walker

    Sep 06, 2015 9:29 AM

    I have been a renal nurse for the past 27years and the last 10 years focusing on self care. I found that by educating my patients about fluid control and its effects if not managed within certain restrictions received the best outcomes. They take control and as a result become extremely proficient in managing both their dialysis and fluid needs. Well done John and Dori for highlighting and pushing this important aspect of dialysis care forward.
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    • John Agar

      Sep 16, 2015 5:51 AM

      Thank you, Diane. I personally think that a volume KPI would make far more difference than ever has the solute one. I note that this blog has been picked up by RenalWeb with an editorial comment suggesting I did not look at the whole picture and that the patient's emotional and psychological health was important too. While the author of the editorial at RenalWeb is correct, perhaps they missed the point of this particular exercise, which was to provide Dori with a 'Volume 1:01" for her meeting with CCSQ ... a meeting which had the express purpose of discussing a volume measure. My blog was not intended to be a over-arching treatise on the whole dialysis treatment paradigm, but to be volume-pointy and volume-specific - expressly for the purposes of her meeting.
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    • Dori

      Sep 08, 2015 3:27 PM

      Thank you for your very kind words, Diane. It sounds as if you are doing a GREAT job teaching your patients! They are lucky to have someone who helps them to self-manage.
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  • John Agar

    Sep 06, 2015 4:46 AM

    Argh ... I give up ... the posts are not translating! Common sense will dictate my meaning.
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  • John Agar

    Sep 06, 2015 4:44 AM

    Some of my previous post seems to have fallen off the page in the posting process. I think you will get my gist, however.

    Point (2) was meant to read:

    2. at a UFR below 10 ml/kg/hr, my patient is in a cardiovascular 'safe zone'.

    And ... my final paragraph was meant to read:

    "I vote for <10 ... wouldn't you? It seems that QIP doesn't seem to think so - but then who am I to judge? Perhaps the thought of re-crafting US dialysis programs to bring the mean UFR down to 10 or less is a step too far."
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  • John Agar

    Sep 06, 2015 4:37 AM

    I probably shouldn't blog my own blog, but it seems that the UFR cut-off point needs more careful thought.

    Dori's summary suggests that QIP has proposed that a UFR >13 ml/kg/hr should be the cut-off point but, when I look at Flythe's graph, I see things differently:

    1. at a UFR <10 ml/kg/hr, my dialysis patient is within a 'safe zone' for cardiovascular risk.

    2. at a UFR >13 ml/kg/hr, my patient has effectively attained maximal risk.

    3. between 10 and 13 ml/kg/hr, my patient's cardiovascular risk is rapidly escalating from 'safe' to 'unsafe'.

    If I were a patient, I rather fancy I would prefer to be <10 and 'safe', not >10 but <13 with 'escalating' risk, or >13 and in all sorts of trouble.

    I vote for <10 ... not <13. Wouldn't you?

    So ... has QIP got it right? I don't think so - but then who am I to judge. Perhaps the thought of re-crafting US dialysis programs to bring the mean UFR down to 10 or less is a step too far.
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    • Dori

      Sep 08, 2015 2:09 PM

      If it were me, there is NO WAY I would accept a UFR greater than 10 mL/Kg/hour, knowing what I know now. I'm sure there is a lot of industry push-back about 10 (vs. 13) because it would mean longer chair times, possible overtime for staff, etc. Too. Darned. Bad. Delivering "minimally adequate" treatment in a way that we KNOW increases the risk of death is morally unsupportable. If we are going to do dialysis at all--a choice we made 50+ years ago--we need to do it RIGHT, and we are not. If CMS would pay for dialysis by the hour, you can bet that next week everyone's treatments would get longer. If they insisted, based on SAFETY, that the UFR cannot exceed 10, it wouldn't. They have a sacred trust to protect the lives of the people whose care they pay for. I would love to see them step up and use that to improve care, instead of letting industry drive the guidelines and rules.
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