Hi Amba
I'm guessing you are an Aussie? I started on Nocturnal last year using blood pump speeds of 225 as that was Prof Agar's suggested speed (he said that he chose it is because it is halfway between 200 - 250. This was my personal choice and I have had great results doing 3x 8 hours and 1 x 5 (300ml speed) a week.
Just for an experiment the last couple of weeks I have just been doing every alternate night ( 3and haf nights per week) but speed of 250. Blood tests tonight so will see if results still good. I don't want to increase my nights if I don't have too or flow rate as my fistula is relatively young.
Prof Agars website http://www.nocturnaldialysis.org/faq_pages.htm
Question on website explains his reasoning.
You use lower NHHD flow rates than we do – why is this and aren’t high flow rates beneficial and necessary?
Your question says you use a blood flow rate (Qb) of 300 ml/min and dialysate flow rate (Qd) of 500 ml/min. We use an average Qb of 225-250 and a Qd of 300. The following reasons underpin our decision …
Initially in 1993-4, when Uldall and Pierratos began the first NHHD program in Toronto, they used a program of 8 hr dialysis/treatment, 6 x week and a Qd of 100 and Qb of +/- 250.
When I visited in 1999 and decided to ‘import’ his program to Australia, he only recently had increased the Qd from 100 to 200 and finally to 300. We chose to use 300 based on his experience at that time.
Since then, others have used even higher rates - see below - but remember, our two programs (Toronto and Geelong) are based, in the main, on 6 treatments/week whereas many of the more recent ones are alternate nights (7/fortnight or ‘3.5’/week). The less frequent the dialysis, the greater the need to up-regulate flows to compensate for the loss of time and to ensure adequate dialysis.
So, what are the positives and negatives of all this?
Clearly the greater the Qd and the Qb, the more efficient the dialysis … but we already were achieving super-efficient and effective dialysis. Our patients’ Kt/V's (the current 'measure' of dialysis efficiency which, incidentally, I do not believe in for a moment nor agree with at all) were far in excess of those achieved by CHD. Our patients were reaching a glomerular filtration rate (GFR) equivalent of 50 ml/min. 2 normal kidneys produce a GFR equivalent of 100 while CHD produces an equivalent of 13 and chronic kidney disease (CKD) just before entry into a dialysis program is usually equivalent to ~8-10. Compare 8-10, 13, 50 and 100 and you will see that NHD is achieving about 1/2 of normal two-kidney function whereas CHD achieves about 1/8th .
As such we felt no need to ‘push' the fistula but to simply 'cruise' with gentle blood flows and a Qd which didn’t risk either the concentrate or the Bi-bag running out before the planned end of the treatment. The initial rationale for a low Qd was to extend the life of the treatment time and thus ensure bi-bag and concentrate continuity. Remember, our NHHD program is primarily six treatments/week.
As we have introduced patients to alternate night NHHD (7 nights/fortnight or ‘3.5’ nights/week) as well as 6/week NHHD.... and here I stress my very strong belief in 3.5/week not 3/week regimes, we have kept our initial Qb and Qd regime for no better reason than it was in our protocol! OK, I know this is not a good scientific reason, but it is truthful! Despite this, we are very happy with our phosphate control, dialysis efficiency and other parameters under both options so I suppose there has been no driving cause to review or change.
As for why higher flow rates are beneficial? ... simply, the more 'passes' that occur between blood and dialysate, the more efficient is the solute removal. There is therefore some theoretical benefit from both a higher Qd and Qb but if one only - which?
Well, a Qd of 500 compared with a Qd of 300 significantly raises solute removal whereas increasing Qb from, say, 250 to 300 has only a small effect on efficiency - certainly a correspondingly smaller effect than changing Qd. In addition, I have a personal belief (founded more in my experience and ‘gut feelings’ than in my scientific head) that higher AVF flows don’t do the fistula much good. So … if a Qb of 225-250 gives good numbers and outcomes, I think I am justified to be happy with it. In my view then, if one flow rate is to be increased, make it the Qd.
