Saturday, 23 July 2011 12:54

Nx Stage at Home -Progress

Written by  Steve Bone
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Had some more problems, this time with the cartridges (the lines and dialyser) where they fail priming at the same stage every time. It happened to four cartridges from the same batch (out of about 27 used so far). However, Kimal are on to this and have sent me some cartridges from a different batch – and so far, so good. My blood results last week very greatly improved, no I am going to see what they are like this week. I’ll be doing my next bloods, probably on Tuesday and I would love to see some consistency. To date the results have been erratic, but like all things, stick with it and allow things to develop. I am using slower pump speeds, and hence longer sessions to ensure I hit the middle molecule(MM)  clearance, e.g. PO4 (phosphate). At the moment I am looking for the balance between phosphate, calcium, and the impact on PTH (parathormone). My PTH has come down, but it still has a way to go.

The suggestion from Kimal is to reduce the Flow Fraction from my set 35, to say 32/33, so to saturate the dialysate more, and by increasing the time dialysed, so improve the MM removal that way.

So, to Flow Fraction. Let me have a go at this.

Flow fraction (FF) defines level of dialysate saturation, a key component of the way the NXStage works, divided by the blood flow rate.

Flow fraction is the ratio of effluent flow divided by blood flow rate. The Effluent is the spent dilaysate plus the UF (ultrafiltration). I am on dialysis at the moment and taking off 2 litres and so this is what is added to the spent dialysate, over a period of 3 hours on today’s session. Once the UF finishes, then the effluent is just composed of spent dialysate, so the Flow Fraction reduces – so it needs to be increased back to the prescription rate, and so shortens the final stage of dialysis. Keeping up?

So, I’ll have a go at expressing that in one line:

FF = (Spent dialysate + UF)/Blood flow rate

There is a fancy formula for working this out a bit more precisely, so if you are interested, let me know.

The longer the dwell time of dialysate in the dialyser, the better the absorption of waste/toxins etc. Better use is made of the dialsyate, and overall the system uses way less water – made this point in an earlier blog post. So for any treatment I am using 30 litres of water, give or take, against in excess of 200+ for a conventional machine. When I last dialysed at home, using a Gambro, my water bills were horrendous, and I was dialysing every other day. Imagine daily! Hmmm, best not!

The key to NxStage is better utilisation of the dialysate, mimicking the way that PD works. It’s, on the face of it, a logical idea, but then armed with hindsight, we can all be scientists! Odd nobody went down this route before. Still, all part of the developing works of dialysis treatment. Long may it continue!

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Steve Bone

Steve Bone

Hi, I'm Steve and have been a dialysis patient on some form of self-care or other since 1990. I've dialysed at home, abroad, in hospital, oh and had a transplant for 7 years. I work in the insurance industry for a City based business, but am very fortunate to be able to work from home 4 days a week. I hope, with my experiences, I can help others on dialysis or those facing dialysis in the future! It ain't so bad! Steve

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