Hdp

Sure does! I hope you don’t mind some more questions though.

  1. Is it the dialysis machines that calculate Kt/V? Or is that something done elsewhere?

  2. And are dialysis machines capable of calculating HDP?

  3. Do these machines keep a log of recent treatments, or are capable of doing that? I’m trying to think like a state inspector who might want to see how treatments have been going before coming into a clinic.

To answer all 3 questions:

1) Is it the dialysis machines that calculate Kt/V? Or is that something done elsewhere?

No … most dialysis machines don’t or can’t calculate Kt/V directly and/or online. While the measurement of Kt/V in real time can be done by solute concentrations in the spent dialysate using ultraviolet light absorption techniques or by using sodium flux as a ‘surrogate’ for urea, both techniques are surrogate marker techniques.

Kt/V - when done - is by pre-urea and post-urea blood sampling and then by off-line calculation using any one of a number of ‘Kt/V formulae’ and ‘Kt/V calculators’ that are out there. And not all calculators use the same formula … and though stdKt/V should be the one that is used, it is not always clear that that is so.

So … how many more error and/or apples v oranges examples do you want?

There-in lies the ridiculousness of the whole Kt/V reliance theory. There-in lies the seeds for distrust and disbelief. My seed grew to Jack’s bean-stalk size, long, long ago. To the point of saying … well, if Kt/V is ‘crap’, what else is there … and along came thoughts of a better way to look at dialysis.

I know that people love a ‘measure’, a ‘number’, a ‘lab’ (to pit it in US terminology). Well, I hate to disappoint, by in my view Kt/V isn’t it. As I have said, it has set a minimum point to aim for. But, that’s all. Optimum lies far beyond an ‘adequate’ Kt/V.

Enough of Kt/V questions - they bore me!

2) And are dialysis machines capable of calculating HDP?

No … but it doesnt take a calculator to multiply the duration B[/B] of a dialysis session x B[/B], the frequency per week. The only ‘iffy’ bit is that in the HDP prposal of Scribner and Orepoulos,[B] (f)[B] is squared.

But as B[/B] can only be a number from 1-7, even that doesn’t need a calculator to work out as the squares of B[/B] are either 2x2 = 4, 3x3 = 9, 4x4 =16, 5x5 = 25, 6x6 =36 … or for the masochists, 7x7 = 49. The only tricky one is the B[/B] for alternate day (or night) regimes where 3.5x3.5 = 12.25.

So … pick the frequency range (squared) and multiply by the sessional duration and you have HDP.

Scrib and Dimitri’s HDP measured B[/B] in hours … but a minute calculation would be best as it allows more flexibility to the generated number.

If we go back to the previous post where I said the mean US sessional duration was between 210 and 220 minutes, for a 3 session per week regime of 215 minutes, the HDP would be f = 3x3 = 9 x t = 215 = 1935. The mean Australian corresponding HDP where mean sessional time = 270 minutes would be f = 3x3 = 9 x t = 270 … = 2430.

NB … both generate the same Kt/V as flow rates in Australia are +/- 100 ml/min lower … and we think that is good, not bad, for the fistula (but that is a whole different story).

If you were to do an HDP on our 35 NHD patients who, between them, do a mean 5.2 mean nights/week and 8+ hours dialysis per session (as a group), the group HDP would be f = 5.2x5.2 = 27.04 x t = 8x60 = 480 … = 12,979

Short daily x 2.5 hours x 6 sessions a week, in contrast would yield an HDP of f = 6x6 = 36 x t = 2.5x60 = 150 … = 5400

By HDP alone, US Conventional HD = 1935, Aust Conventional HD = 2430, US Short Daily HD = 5400 and Aust NHD = 12,979.

I rest my case.

3) Do these machines keep a log of recent treatments, or are capable of doing that? I’m trying to think like a state inspector who might want to see how treatments have been going before coming into a clinic.

How you make this a regulatory requirement is difficult. I can see many ways to circumvent any regulation that requires an accurate reporting of B[/B], if one had a mind to do it. The machines all have time logs (to the minute) that record running time - but most don’t differentiate between tick-over time between sessions (= bad t) and tick-over time during a session (= good t).

It ought to be easy to in-build a system that could detect actual dialysis B[/B] vs bypass B [/B]or prime B [/B]or purring-in-a-corner machine activity (t) … but that’s not a discussion I would plan to have here - that’s a question for the techs and regulators to solve.

How to fool-proof the system so it doesn’t depend on human recording … I have no idea. At the moment, it wouldn’t be possible - or if possible, is unlikely to be done - reliably and with certainty.

So … there you have it … finally, a brick wall!

I see the light! And I see a brick wall that I hope can someday soon be circumnavigated.

While things were bubbling and boiling in the back of my mind, something did pop out about your GDI. If things go according to plan, I should be bumping into a few nephrologists - I’m thinking I ought to bring along printouts of your GDI. In my more aggressive days, I did like to take postcards I got from Home Dialysis Central and put them on the windshields of autos at some of the local clinics - wouldn’t be a big deal to hand out some printouts.

Anyway, thinking usually gives me headaches - but I will try it anyway with what you have given me.

Chris

Plugger - maintain the drive!

Don’t for a moment think I am trying to dampen your enthusiasm to seek a better way … never! It’s just that there are points in the process where one feels (or gets) stymied.

In the end, and this is a personal conclusion, I believe more in a big t, than I believe in a big K.

That is not to say that the factors that drive K are not important too … they still are … it is just that, in my view, K has come to dominate the broader thinking and t has been rather sacrificed to K.

While K matters, I think the emphasis to beef up K and ignore t - or more accurately, to minimize t because its seen as a patient (and financial)-friendly thing to do - has come at a huge outcome and survival cost and that the equation should be re-balanced by ensuring a greater t.

Remember though, that if you leave the factors that comprise K largely alone and just improve (or lengthen) t, that the multiplier on the numerator line (K x t) will enlarge. For a Kt/V believer, that still improves the overall ‘outcome’ - if Kt/V is an ‘outcome’.

So … a longer t is the goal, let the rest look after itself.

As for regulating, mandating, measuring and ‘quality-assurancing’ (is there such a word?) for t, that’s another matter altogether - and one for a techie to solve.

Thanks for the encouragement! To tell you the truth, I don’t think I have much choice. I felt like I did my civic duty back in 2007 when I helped head up a group that put through a Colorado bill for certification of dialysis techs - but something inside won’t let me be, even to the point of going through insomnia. So if all I ever get out of this is a good night’s sleep, I’ll be happy!

Sometimes I feel like Bill Cosby’s Noah. If you never heard his comedy routine, it is a riot: