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!