Scribner's formula: where does BFR and dialysate volume sit in this

[amanda100wilson]

I am a great believer that Scribner's formula (adequacy = frequency squared x time) is a better measure of whether a patient is getting adequate dialysis.  How does BFR and dialysate volume factor into this.  Is it simply that a lower BFR and greater volume will give you a longer time?  I hope that this is not a stupid question, but I want to get a better understanding of this.  I wish the whole thing was simple.  I struggle with trying to balance what is right for my health, versus terms what is right for living my life (and my sanity because I have been unable to sleep on extended , and sitting in the chair for any longer than four hours drives me to distraction and eats into my day!)

[obsidianom]

I am a great believer that Scribner's formula (adequacy = frequency squared x time) is a better measure of whether a patient is getting adequate dialysis.  How does BFR and dialysate volume factor into this.  Is it simply that a lower BFR and greater volume will give you a longer time?  I hope that this is not a stupid question, but I want to get a better understanding of this.  I wish the whole thing was simple.  I struggle with trying to balance what is right for my health, versus terms what is right for living my life (and my sanity because I have been unable to sleep on extended , and sitting in the chair for any longer than four hours drives me to distraction and eats into my day!)

Tha formula is a good guide but it also is limited as it is for standard dialysis , not specifically Nxstage. It doesnt take into account dialysate volume .
I like the general rule Dr. Agar writes about , that you need at least 10% of total time on the machine. That comes out to about 17 hours per week.
Now on Nxstage that assumes you are using the correct formula they give for volume of dialysate on the online calculator. Then you run the dialysate slow enough to get 17 hours per week.
For example we run 30 liters per treatment, 5 days per week. To get 17 hours we run 3.5 hours per treatment(17.5 hours). So we slow down the dialysate to about 8.5 liters per hour to go 3.5 hours. The blood speed is a constant at 340 . That also goes with Dr. Agars writing that blood speed  should be at or below 350  to save the fistula and not stun the heart. Since we upped the time from 3 hours to 3.5 the results have been better. The extra 2.5 hours per week has helped a lot.

[Hemodoc]

The Hemodialysis Product is validation of the Middle Molecule hypothesis and has been rejected in large part by the American nephrology community who remain fixated on urea clearance measurements. Middle molecules are larger than urea and are believed to have more of a role in uremic toxicity than urea which is held as a non-toxic uremic component. Urea is cleared very quickly and easily especially with high flux artificial kidneys in wide use today.

Middle molecules on the other hand are larger molecules ordinarily cleared by the kidney that are poorly cleared even with high flux artificial kidneys. The manner in which to clear these middle molecules is by increased time and increased frequency of dialysis.  The Hemodialysis Product is a direct result of evidence based medicine in large part based on the Tassin France experience of dialyzing patients 5-8 hours in-center. Bernard Charra learned his techniques from Scribner in Seattle and is one of the few clinicians who continued the original thrice weekly 5-8 hour sessions as developed in the early years of dialysis in the 1960's.

Dr. Charra has published his results with profoundly improved outcomes compared to the standard thrice weekly 3-4 hours regimens dealing in large part with extended dialysis sessions coupled with strict sodium restrictions. In doing so, 90% of his patients become normotensive without any hypertension medicatioins.

The Scribner/Oreopoulos Hemodialysis Product utilizes the Tassin data and other sources to postulate that TIME and FREQUENCY are related to improved outcomes in a mathematical relationship that is measurable and predictable.

In such, phosphorus which is a smaller molecule but acts in the same fashion is easily cleared by NxStage with extended daily regimens often requiring phosphorus supplementation. In such middle molecule clearance is much less volume dependent than it is TIME dependent noting that the Kt/V of a 20 L NxStage treatment over 2 hours or 8 hours has the same clearance yet for PO4 the clearance of PO4 is dramatically improved by TIME without any added volume. Not that increased volume is not important in my opinion with NxStage, but the MOST important parameter is TIME and Frequency.

I have considered the HDP in designing my own treatment regimen and I believe it is still valid in the NxStage application because of the middle molecule theory.

You can read the article here directly to here how Scribner described his measurement. Once again, this advance has not met with the critical acclaim it should have to date, but that is once again a unique American issue unfortunately with our industry plagued by greed.

http://www.therenalnetwork.org/qi/resources/HDP.pdf