Is turning the utrafiltration off ok?

westieluv · Feb 19, 2014

I am fairly new to dialysis (9 months now), but at our clinic, as well as in our acutes department, we are never to turn the UF completely off. The minimum we can go is 300 ml/hr. and if that is not sufficient to stop the cramping or hypotension we give fluid back. It would take someone with more experience than me to give you the rationale behind that policy, but at no time do we ever completely turn off the UF, even if we are not to remove any fluid. We simply set the UF rate to 300 and return whatever we remove.

NurseRies, BSN, RN · Feb 19, 2014

I know that if a person is crashing or cramping etc that it is acceptable to turn the uf off until the patient is stabilized then turn it back on. My question is can you leave the uf off for an extended amount of time without having any harmful effects or decreasing clearance? A lot of nurses that have many years experience say not to but there are doctors now that say it is ok. Can anyone explain the different reasonings for this?

It is a manufacturers recommendation. If you use the Fresenius K machines, the manufacturer recommends no less then300ml/hr. If UF is off or too low, supposedly you won't get great clearance. If you use the Phoenix machines, the minimum rate is 100ml/hr per manufacturer. I have asked this question many, many times. And this is always the answer. Doctors and nurses have either told me it didn't matter or it truly did. But if you want best results from dialysis, I'd go with what the people who made the machine recommend. It has to do with convection and pressure going in and out of the dialyzer (I think lol.. So they say). They say if you aren't pulling off some fluid, then the particles have nothing to travel with out of the blood stream. It makes sense, but it's usually not a nursing policy, more of a recommendation for best clearance. Replace with saline if you must, go with your policy. Personally, I never turn the UF off unless the patient is in tears cramping. You should always set the machine to at least remove prime.

Just explain that to docs and they have always agreed. "I see here you wrote for no UF, but the manufacturer recommends a minimum UFR of 300ml/hr to achieve optimal clearance and best treatment, is that ok? I will replace with saline, flush 100ml every 30 minutes. " if they say no , ok--The patient will still get HD, but it won't be as effective. Clearance also goes down if you reverse the lines, low bfr, low Dfr, or clotting in the dialyzer.

westieluv · Feb 19, 2014

It has to do with convection and pressure going in and out of the dialyzer (I think lol.. So they say). They say if you aren't pulling off some fluid, then the particles have nothing to travel with out of the blood stream.

That makes perfect sense. How can we pull off potassium, urea, etc. if it has no medium in which to travel? it seems like it would just pass through the dialyzer with the other blood components.

NurseRies, BSN, RN · Feb 19, 2014

That makes perfect sense. How can we pull off potassium urea, etc. if it has no medium in which to travel? it seems like it would just pass through the dialyzer with the other blood components.[/quote']
Yes the dialyzer is made up of small fibers that also "catch" particles, so some clearance will still occur. But if you think about it like a flushing or washing out, more excess electrolytes and urea will be removed with both mechanisms working towards best clearance. The filter catches a lot of the molecules. I am learning a lot about CRRT using the prismaflex right now. I know it is different in many ways, but I'm learning more about how the processes actually work and it's awesome! Have you ever dialyzed a septic patient or a really sick patient who almost immediately clots? That's because the dialyzer or filter is catching all the Lactic acid and CKMBs (don't quote me on this since I'm going by memory), but really septic patients will rapidly clot a filter. On the other side though, if a really sick patient has a platelet count of 45, I doubt they will clot even if really septic. Just learning about the clotting cascade. It's all interesting to me. Even after a year of doing dialysis, I really didn't understand things properly. I've had several "ah-Ha" type moments that really helped me understand how all these technical treatments actually work! Going into my fourth year now and still learning more and more... It's nice to have a specialty.

nurseREA · Feb 19, 2014

Thank you for the info! It has helped me understand it a little bit better.

kdunurse · Feb 20, 2014

I thought that most of the waste products are removed through diffusion rather than ultrafiltration, and that ultrafiltration regulated the amount of fluid removed. Some solute will be removed with the fluid, but it can still diffuse across the dialyzer membrane when the UF is off. The only time there is no waste removal is during SCUF, when the dialysate flow is turned off. I've never heard of having to keep the UF on during dialysis - in fact, we have one patient on whom we do dialysis with the UF completely off throughout the treatment - she's not my primary patient, but I'm pretty sure her numbers are good.

NurseRies, BSN, RN · Feb 20, 2014

to kdunurse-- I think you're absolutely right. You will still have clearance with the UF off, but it won't be as good. Just like you could reverse the lines on someone's treatment every single time, and they still manage okay, they just aren't getting the maximum clearance that is possible. HD is diffusion, UF is fluid removal, but there is a recommendation to get the best diffusion, you have to use both modalities. I have worked at hospitals where the nurse managers says it doesn't make a difference. But I know that many large companies have it written into their policy to have the minimum UFR at 300ml/hr. This is because of manufacturer recommendation. That is all I can say. I have tried to look up literature and articles and can't find anything of the sort on the topic. After asking many nurse managers and experiences dialysis nurses, the majority of them agree, it is always best for the patient to have the minimum UFR recommended for treatment. We can't always accommodate, but it is something to think about.

MMAnurse · Feb 23, 2014

Within my company which is a large, worldwide company (no names mentioned) the UF is never turned off, with a lowest being a 300 UF. Unless if course the pt is on a PUFF tx.

Chisca, RN · Feb 23, 2014

Even with the UF removal off solutes are removed because the concentration gradient is still there. 10 on one side and 3 on the other means that diffusion will want to balance the solutions whether are not water wants to come along. Water is not removed by diffusion but by augmenting the pressure in the dialsate solution. The only thing you lose with the UF off is the removal of some particles by convection. Convection was a hard concept for me to understand but I look at them as hitchikers. But if your QD is going by at 1.5x your QB you still have some convection.

MMAnurse · Feb 23, 2014

Tha k you so much for that explanation Chisca. I had no idea some solutes were still removed with UF off:)

gollybabbler · Feb 28, 2014

There's also the concept of "backfiltration", (paraphrasing work info here) which is the movement of fluid from the dialysate compartment of the filter into the blood, and can occur with minimal fluid removal & when the TMP is low; potential contaminants in the dialysate can be transported across the membrane. This is why minimum UF is used, instead of turning it off completely.