Question about Ultrafiltration

[HubbysPartner]

My husband and I have noticed that even though we program a certain amount of fluid to be taken off, it doesn't show in his post treatment weight.  We have actually had times where his before and after weight was the same!   Sometimes he will have a small snack during treatment, but usually doesn't drink anything, so I don't think he is adding weight during treatment.   Is there any way to know for sure how much fluid is taken off? 

[RichardMEL]

The snack will add some weight. For example during my treatment we get given some sandwiches which, by observation, I have worked out add around 150g of body weight (not expelled during the session). The other thing to take account of is the "washback" (a.k.a. rinseback) amount. When we calculate UF total to take off we add 500ml for this, because of the saline pushed in as part of the washback. If you're not taking account of that when computing the UF goal, and you're only taking a small amount off, then that could account for the weight changes.

Also how sensitive are the scales you are using? There may well be a degree of error - again specially if you're talking about taking off small amounts (eg: under 1000 ml).

[nursewratchet]

Are you on In center or home.  If you are figuring the weight yourself, be sure to add 500 cc for the rinseback.  If he does routinely eat or drink, add that.

[HubbysPartner]

We are doing home hemo with nxstage.  When he has a snack, I usually weigh it so I know how much he has (usually about 28g of pretzels).  We were told that the machine automatically accounts for rinseback so we don't have to put it in our figure.  Is it possible for the machine to think it took off what we programmed, but the fluid didn't actually come out of him?

Also, we have a new digital scale that sits on the kitchen floor (tile).  I would think that if the scale is off, it would be off both times, but the weight difference would be the same.  Any thoughts?

[funnygarcia]

We were told that the machine automatically accounts for rinseback so we don't have to put it in our figure. 

It does only if someone has set it that way in the parameter screen. It's an option to have it set, not a pre-set parameter.

Also, dh had asked about this same situation when in his training center (short term training to use catheter while waiting for new fistula to heal). He used one of their machines, added extra to account for rinse back, his post weight was the same as pre weight. He asked the nurse and was told the cycler works on a pressure basis (how much pressure goes thru the dialyzer) and assumes fluid comes off based on that pressure. Over time the cycler doesn't measure as accurately and needs to go in to be serviced.

[M3Riddler]

Not sure if you mentioned this, but how much of a difference is there on an average tx that you are off on your weight?

///M3R

[HubbysPartner]

It can be off anywhere from .3 to 1.0.  We spoke to NxStage and they told us there can be a variance of up to 3%, so I guess we're not off as much as we thought. 

[Malibu]

We had this problem one day in training, it turned out that because the scale (of the flat electronic variety you mentioned) was moved it had given an erroneous weight.  Becaues we moved it it had to be rebalanced. 

We also were told that the Nxstage automatically calculated in the rinseback.

[rocker]

Yes, the NxStage does the rinseback.  Ever notice that if you program it for, say 0.8/hr rate, after 30 minutes it will only be down by .1 or .2?

That said, yes, I was also told by NxStage that the allowable error is 3% of total treatment.  So if you're running 25l, and removing 3l, the allowable error is (25 + 3) * .03 = 840 ml!!  That strikes me as a lot to be off, but.....not much I can do about it.  I've taken to relying on pulse rate as much as the machine to determine when he's dry, since I know how his pulse and bp reacts.  With our machine (no doubt yours is somewhat different), I just generally add .3 to the calculated amount right at the start.  Then when we hit 5, I tell him what I've taken off, what his vitals are, and ask if he wants more off.  Then I'll add UF .1 or .2 at a time until we both feel he's dry.

But yeah, we often end up off by .4 to 1.0.  It's just something you get a feel for over time.

[HubbysPartner]

I'm glad to know it's not just us.  However; it is very frustrating to try to figure out how much will be taken off.  We have started adding .5 to whatever we decide to take off and we still end up off by up to .5 or more.     Oh well, as long we get close to his dry weight, I'm happy. 

[Zog]

You might need to get a new scale.  We don't use the scale the center got us after episodes like yours.  We switched to a weight watchers scale from Target and it seems to do okay.  You may want to wait 5 minutes and check the weight again.  Or you can weigh your self and then your husband.  Scales like variety for some reason.

Our NxStage rinses back 277 ml at the end of treatment.  It used to be 273 ml with the old cartridge.  We always add 300 ml or .3 kg to the preweight.  You can tell how much it rinses back because of the number it counts down from during rinseback. 

Get familiar with your settings sometime (hold treatment button down when starting, read manual for setting numbers and codes), you will want to write all of these down somewhere or get a list of what they should be from the center.  If your machine ever breaks down and you another one from NxStage (some courier dude will show up at your house from the airport with no idea what he is carrying), you will have to reprogram all those settings before you can use it like your old machine.  If they change the cartridges again you will probably have to change these settings.  If they change your FF or your dialysate total you will have to change these settings.  We turned up the green number scrolling speed.  We got tired of waiting for the time remaining and pressures to read out.

[HubbysPartner]

We bought a digital scale and I tested it using things with known weight, so I'm pretty sure it's accurate.  My hubby has also weighed himself several times and it usually comes up with the same weight.  Good tip about the scrolling speed though, it is a pain to have to wait so long for each number.  I will look at the other settings.  We just add a little to the target UF and it seems to be coming out ok for now.

[Malibu]

NxStage at home since Jan 2. MM has been weighing-out the same as he weighed-in most days.  We typically remove .2 a day, every once in a while he will weigh in at 1 or 1.4 and for some reason when he weighs-out it has removed more than we said to.  Very strange...I just figured it was the nature of the beast.  We assess edema and as long as he is good then we just continue on...