A New, Dialysis Fluid Restriction Calculator

A New, Dialysis Fluid Restriction Calculator
May 13, 2021 0 Comments

Over the previous few years, the great dialysis pendulum has lastly—if a bit belatedly—swung away from a singular concentrate on solute clearance (seemingly mounted on the incorrect solute) and in direction of understanding quantity and the methods to realize optimum quantity administration.

I’ve written various blogs like this one (https://www.homedialysis.org/news-and-research/weblog/113-how-much-can-i-drink-doc) for KidneyViews on the central significance of quantity in each the intravascular and extravascular areas, and absolutely the dialytic crucial to change it gently, and slowly. A number of litres of fluid merely can’t be eliminated in a rush. Brief, sharp, excessive UF dialysis lays a fast path to circulatory instability and organ stun: the center, the mind, the intestine, the muscular tissues, the residual kidneys…all and any are threatened by the fast fall in perfusion (blood circulation) and tissue oxygenation that accompanies the sudden discount in blood quantity and it’s surrogate measure, blood strain, that brutal dialysis brings.

Within the dialysis hours—and they need to be lengthy, not quick—the dialysis prescription holds the important thing to slower quantity change. That is primarily achieved by a mixture of longer session length and better session frequency. Each matter. Every compliments the opposite. Every wants the opposite.

However there may be multiple option to pores and skin a cat! What is finished inside the hours of dialysis is basically ours to regulate, however exterior dialysis classes, the affected person is, to all intents and functions, on his/her personal. Within the 12 – 15 hours of typical centre-based care, the machine and the prescription have management, however within the 143-146 hours/week the place the affected person is away from the dialysis unit, the affected person is in sole management. The treating workforce has little or no management over that important interval past giving the standard post-dialysis exhortations to restrict fluid consumption, restrict sodium, restrict “moist” meals (like watermelon), and so forth. However, on the subject of the encouragement to “restrict fluid consumption,” it begs the query: “By how a lot?” Right here, we flounder …

It’s clear that the charge of fluid removing—the ultrafiltration charge (UFR)—issues, and issues deeply, although there stays disagreement over what that charge needs to be:

  • Charles Chazot (Tassin, France) has knowledge to indicate that perfusion damage begins to happen because the UFR rises past 6-7ml/kg/hr.

  • In our personal service in Geelong, Australia, we now goal to maintain, and we largely obtain, a cross-service UFR of <8ml/kg/hr, though I confess to suggesting a UFR most of 10ml/kg/hr solely 2-3 years in the past.

  • In 2010, the Facilities for Medicare and Medicaid Providers (CMS) proposed a UFR of <15 ml/kg/hr because the fluid removing charge goal,, although this was revised downwards to a suggestion of <13 ml/kg/hr in 2016.

  • Within the US, the presently really helpful goal UFR is <13ml/kg/hr—regardless of that Jennifer Flythe confirmed compelling however imperfect knowledge in 2011 from a re-working of the HEMO trial that advised a fast ramping of all-cause mortality and cardiovascular danger occurred because the UFR rose above 10ml/kg/hr.

As but there is no such thing as a worldwide settlement on which charge (or which “suggestion”) is appropriate, however Chris McIntyre’s group has clearly demonstrated that the sooner fluid is eliminated, the higher the chance of tissue misadventure by hypo-perfusion and oxygen deprivation. Although clearly extra work is required on this house, I’ll let the reader attain his/her personal conclusion about the place higher restrict for the speed of ultrafiltration ought to seemingly lie. One factor is definite: the length of the dialysis session is the one rational option to management the speed of fluid removing, and slower means longer.

Simply as clearly, the quantity of fluid that should be eliminated, estimated by its surrogate, interdialytic weight (IDWG), can also be crucial. Drink extra, achieve extra, and there may be extra to take away! In flip, this could solely translate into sooner removing, or an extended dialysis session. With out exception, the latter is the higher choice, although sadly and all too usually, it’s the removing charge that’s ramped up inside a unusually immutable quick session time slightly an apparent—however prevented—session extension.

Mel Hodge wrote an erudite weblog on the “damaged” US for-profit dialysis enterprise mannequin (https://www.homedialysis.org/news-and-research/weblog/117-it-s-past-time-to-destroy-the-dialysis-business-model) suggesting that if dialysis have been reimbursed by the hour, longer dialysis classes would instantly consequence—to the good thing about the affected person, slightly than the supplier. Although clearly the very best answer I’ve ever seen for the unusually quick dialysis practices of US suppliers, as but there appears little urge for food for change.

The “strategies” taken to restrict interdialytic weight achieve are as restricted as is their success. Salt restriction in all, and sugar management in diabetics, are our cornerstone directions and chief weapons in opposition to extreme inter-dialytic fluid positive aspects, and a excessive subsequent UFR. In sequence, then, a excessive UFR results in on-dialysis cramps, nausea, vomiting, crashing BPs and “flats,” post-dialysis torpor, and a raging post-dialysis thirst. The dried-to-a-crisp affected person is left to limp residence after dialysis to hoe into pickles and salt—no matter something we’d advise on the contrary. Whereas we plead: “drink much less fluid,” there is no such thing as a science, and no formulation, to information a reasoned stage of fluid consumption.

And so to the purpose of this weblog:

…I’d love a buck for each time I’ve heard a dialysis affected person ask, “So, how a lot can I drink, John?

We ought to know the reply, however, oddly, we nonetheless don’t appear to have ever thought by a smart reply to this easy query. Too usually a response is prevented, or prompts a suggestion like, “500 ml + urine output.” The literature is filled with this poorly suggested recommendation; an oddly inconsiderate instruction that pays no heed to affected person measurement, age, gender, dietary standing, or dialysis prescription. 500 ml for a forty five kg aged girl is not the identical as 500 ml in a 120 kg teen, regardless of urine output!

However, all of the mandatory parameters to foretell and advise a secure, individualized fluid restriction, and a secure ultrafiltration charge through the subsequent dialysis are recognized! Work although this easy train to determine an individualized fluid restriction (FR):

  • IDWG – interdialytic weight achieve will be measured. It’s physique weight previous to the upcoming dialysis minus the burden on the finish of the final dialysis.

  • UO – the typical every day urine output will be measured.

  • DI – the dialytic interval is thought: it’s the length from the tip of 1 dialysis to the meant begin of the following (generally 1-3 days).

  • SD – the session length (SD) is thought. It’s the meant, prescribed length of the upcoming dialysis remedy (mostly between 3 and 5 hours).

  • TW – the goal weight is thought (or needs to be) … it’s the weight the nephrologist has suggested needs to be the goal to realize by the tip of dialysis.

Utilizing these easy measures, an equally easy formulation will be devised that individually advises the required fluid restriction, remedy by remedy, that may make sure that the following dialysis session will obtain any desired ultrafiltration charge, understanding the interval to the following remedy and its’ meant length.

For these within the arithmetic, right here is the formulation:

Truth 1
IDWG in Kg = [FR in mL – UO in m:] x DI in days.
IDWG = [FR – UO] x DI
Truth 2
As IDWG in Kg = the specified upcoming UFR mL/Kg/Hr x SD in hours x TW in Kg,
then, IDWG = UFR x SD x TW
Truth 3
As every formulation equates to IDWG, one should equal the opposite.
[FR – UO] x DI = UFR x SD x TW
Closing Components
FR = [(UFR x SD x TW) ÷ DI] + UO.

This formulation can simply be transformed right into a easy calculator to advise interdialytic fluid restriction, utilizing the next knowledge set by the doctor:

As well as:

  • Dialysis interval is often decided by the dialysis roster.

  • Interdialytic urine output is a quantity that ought to most likely be re-measured as soon as each couple of months, because it tends to slowly decline in most sufferers over time. That is the one required affected person enter.

This formulation then informs a solution to the query, “How a lot can I drink, Doc?” backed by some easy science and permitting patient-centred individuality. This appears a more sensible choice than both guessing, and even avoiding the problem utterly. Thus, it lastly turns into doable to realize the important thing end result: a desired, secure, and predictable UFR for each dialysis.

Whereas FR = (UFR x SD x TD) ÷ DI + UO has not but been validated or examined in opposition to massive populations, a requisite step to realize extensive acceptance, particular person dialysis companies are inspired to play with it in parallel with their different fluid restriction practices and see if it really works and helps.

CAVEAT: Till the formulation is validated and any populations the place it might not be dependable have been recognized, it ought to solely be used as a parallel support, not an infallible predictor. It might not be dependable in youngsters, in low weight adults, or in those that are very heavy. The constraints of the formulation—and there’ll undoubtedly be some—have to be totally understood. However, trial use in our personal affected person inhabitants means that for many, it really works effectively.

The Medical Schooling Institute (MEI) by its Residence Dialysis Central website has constructed the formulation into an open entry Dialysis Fluid Restriction Calculator.

Use it right here https://join.calcapp.internet/?app=2adoxr#/ or set up it to your homescreen in your cell gadget to make use of offline!

MEI already printed the Barwon Well being UFR calculator we developed in Geelong, Australia in 2014 [see: https://www.homedialysis.org/ufr-calculator], a useful resource that many sufferers, particularly these at residence, discover helpful. Tell us what you consider our Dialysis Fluid Restriction Calculator. You could even prefer to recommend a greater identify for it!


Up to now, solely two choices exist to regulate the UFR most throughout anyone remedy:

(1) Extension of session time to limit the UF charge

(2) Limitation of IDWG to cut back the necessity for an extreme UF charge

Whereas longer dialysis classes stay the very best and optimum answer for extreme interdialytic weight positive aspects, the introduction of variable extensions of session time can be, not less than for many companies, logistically advanced. Because of this, a easy formulation that individualizes the interdialytic fluid consumption for every interdialytic interval is a pretty different alternative.

A easy calculator developed at Barwon Well being, Geelong, Australia, and translated into an Web useful resource by MEI, Madison, Wisconsin, could assist reply the age-old dialysis affected person query, “How a lot can I drink, Doc?”

For centre-based sufferers, dialysis nurses will be capable of work with every particular person on the finish of every remedy to advise a extra structured fluid restriction plan, understanding the interval until the following, the length of the following, the goal weight for the following, and the standard interval urine quantity earlier than the following dialysis remedy. This could guarantee a volume-safe dialysis the following time spherical, each time spherical, assuming a smart UFR most has been set.

For residence sufferers, self-entry/self-selection of the identical knowledge set into the calculator ought to allow a fluid consumption plan to evolve.

If IDWG and fluid restriction will be higher suggested, it needs to be doable to forestall the frequent want for extreme UF charges throughout dialysis, and the chance(s) of organ hypo-perfusion and “stun” ought to thus be lessened.


  1. Chazot C et al. Even a Average Fluid Elimination Charge throughout Individualised Haemodialysis Session Occasions Is Related to Decreased Affected person Survival. Blood Purification. 2017: 44. 89-97. See: https://www.karger.com/Article/Pdf/464346. –

  2. Agar JWM. Private Viewpoint: Limiting most ultrafiltration charge as a possible new measure of dialysis adequacy. Hemodialysis Worldwide. 2016. 20(1). 15-21. –

  3. Arbor Analysis Collaborative for Well being and College of Michigan Kidney Epidemiology and Price Heart: Scientific and Information Technical Skilled Panel Conferences Synthesis Report, 2010.  https://www.cms.gov/Medicare/Finish-Stage-Renal-Illness/CPMProject/Downloads/ESRD2010TechnicalExpertPanelReport.pdf. –

  4. Nationwide High quality Discussion board #2700: Ultrafiltration charge higher than 13 ml/kg/hr.  http://www.qualityforum.org/ProjectTemplateDownload.aspx?SubmissionID=2700. Accessed Could 31, 2016 –

  5. Flythe JE et al. Fast fluid removing throughout dialysis is related to cardiovascular morbidity and mortality. Kidney Worldwide 79(2). 250-257 –

  6. McIntyre CW. Recurrent circulatory stress: The darkish aspect of dialysis. Seminars in Dialysis. 2010; 23:449–451 –

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