Dialysis: a Duopoly of Solutes and 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:
- 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.
- 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.
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:
- 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!
- 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
- 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.