If yes how long can we use isolated UF ?
and in isolated UF can we have reduction of BUN and Creatinine and potasium ?
Isolated ultrafiltration is sometimes used to reduce volume overload, e.g. in anasarca, cardiac failure, nephrotic syndrome, excessive volume overload. The isolated ultrafiltration is well tolerated because no reduction of BUN, Creatinine and Potassium occur. The blood pressure is stable. For reduction of metabolite products normal haemodialysis or haemodiafiltration should be used.
Certainly agree with Oskar. Isolated UF can be done in the first hour of hemodialysis. However, it has not been established as yet whether this can have an impact on electrolytes such as serum K. Due to this, I routinely check pre HD serum K before performing Isolated UF. Theoretically, you would think that as you dry out the patient, the serum K levels are expected to rise. So, for a patient requiring isolated UF, but presenting with hyperkalemia at the same time, I would not recommend Iso UF immediately.
Ultrafiltration is an alternative strategy to diuretic therapy for the treatment of patients with acute decompensated heart failure or excessive fluid overloading. However, it is not appropriate for eletrolyte imbalance such as hyperkalemia or severe metabolic acidosis.
Dear Edward
Do you mean no electrolyte passes the filter during Iso UF ? then what is the difference between HD and iso while the base is convection and the filter is the same ?
yes, we use the same dialysis filter -- no dialysis or eletrolyte change -- only convection.
Agree with Chen. The issue is whether Iso Uf has an impact on the electrolyte levels though. We know that with for instance, Hb as you take fluid off , Hb levels go up. If the same principle applies to electrolytes such as K, then we need to be careful when performing Iso UF to patients with hyperkalemia especially in the first hr.
Isolated ultrafiltration used to be popular in the ancient times of dialysis, when bicarbonate dialysis solution were not available and acetat based dialysis solution used to make patient prone to hypotension. Using modern high flux dialysers, bicarbonate dialysis solutions or hemodiafilatration make isolated ultrafiltratiion rather obsolete. There is big risk of mistaking hyperhydratation and hyperkalemia in chronic dialysis patient. Launching isolated ultrafiltration or waitting for the lab results in the case of symptomatic hyperkalemia can have death consequences. On the other hand high volume isolated ultrafiltration is well tolerated in the case of hyperhydratation.
The aim of isolated ultrafiltration is reduction of volume overloud without osmolality reduction. It can be useful for hemodynamic stability and prophylactics disequilibrium syndrome in dialysis patients or for treatment of a volume overload without uremia. Reduction of BUN and Creatinine and other metabolites will be equal to their content in the ultrafiltrate, so it should be insignificant. That is why - if you use isolated ultrafiltration for treatment dialysis patients - the time for procedure should be proportionally increased.
We sometimes use isolated UF in markedly hypervolemic patients to easy shortness of breath. An alternative is to start dialysis without connecting the venous line. Therefore, a circulatory volume reduction of approximately 100 to 150 ml (depending on the volume of the extracorporeal circuit) is reached and often may resume the patient´s symptoms or may at least may relieve dyspnea to some extent.
Practically, I agree with most what have been said.
My question is: what is your indication to use it? In other words: what is the case that you are planning to use it?
I think to have replied to this question in past time, even replying to a different form of the same question. As already very correctly replied by the many colleagues above, isolated ultrafiltration can be usefully used as a treatment per se, in case needing to reduce the body water in various clinical events, not necessarily linked to renal insufficiency, as in case of heart congestive insufficiency, but also at hemodialysis seance starting, maintaining in the following time ultrafiltration zero, or subtracting at the first time with isolated ultrafiltration the greater part of weight gain and the remaining water in the following by marginal removals per hour. This strategy is very useful in patients suffering of cardiovascular instability in case of water removal along all the time of a standard treatment
Isolated ultrafiltration can be used for the first hour of hemodialysis in overhydrated patients with severe dyspnoe.
Isolated ultrafiltration is a simple technique used for removing fluid overload . However if you start dialysis after ultrafiltration you can have a decrease of blood pressure . So , in my opinion , is better to begin with dialysis and to apply ultrafiltration at the end . Remember that ultrafiltration does not modify electrolite serum concentrations and that you can have an increase of serum potassium . When do i use ultrafiltration ? When i have a pt that is overhydrated and difficult to arrive to the dry weight especially at the third dialysis session of the week . Ultrafiltration is not dangerous , overhydration is dangerous .
There may not be a big difference between three methods of removing fluid by ultrafiltration (UF) whether it is done before or after or during the whole dialysis procedure. If the time taken for the whole procedure is limited by scheduling issues etc then adding UF as a separate process would shorten the actual dialysis time. Conversely if you commit to spending more time on the whole treatment, why not spend the time to allow you to remove the fluid slowly over the whole treatment as we do during the conventional dialysis process? The removal of volume during conventional dialysis is achieved by applying pressure across the dialyzer membrane. It is really no different than doing isolated ultrafiltration. But you can spread the filtration over a longer period of time causing slower volume shifts in the patient. There is the competing process of disequilibrium affecting volume shifts in the patient but I will leave that to another time.
If you have a pt overhydrated ( 5 - 6 kg over dry weight ) , which is your strategy ? Removing the fluid slowly ? I am waiting for an answer.
It depends on how the patient presents. Do they look compromised with that fluid? How long have they been carrying the fluid? How do they feel? Do they actually need to have all the fluid off or they need their base weight to be reviewed? What day of the week is it? Did they have a longer break? Answering these questions will help you to know whether you need to remove the fluid urgently or not.
Dear Ennio
if it is not emergency i try to increase the hemodialysis session and if so i increase the time .
Dear Ennio
if it is not emergency i try to increase the hemodialysis session and if so i increase the time .
The reply of Dr Zimbudzi replies very well to the numerous aspects of treatment of an over fluid condition. But if I would add something, A vascular overcharge of 5 - 6 kg is not something to be easy suffered for many hours by a chronically dialyzed patient, all of them being notoriously affected by an alternating condition of a less or more great overcharge and always presenting less or more important heart damages . So I think that independently from the day of the week and from the day of stated new dialysis seance should be advisable to undergo the patient to an isolated ultrafiltration as soon as this treatment could be done.
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I think I could make an argument for doing hemofiltration (HF) at the end of dialysis. In 1977-1980 I worked on building three pool mathematical computer models of fluid and electrolyte shifts in patients undergoing hemodialysis. These days you are probably aware of dialysis disequilibrium but I will describe the fluid shifts here.
As various chemicals are removed from the blood by diffusion across the dialyzer membrane their concentrations drop. (This doesn't happen with ultrafiltration.) Unless these solutes move across cell membranes very quickly a concentration difference develops between the intracellular compartment (ICF) and extracellular compartment (ECF).
Since the extracellular compartment becomes more dilute it drives osmosis which is really diffusion of water down its own concentration gradient. A lower solute concentration in ECF means a higher water concentration in the ECF. So water diffuses into the cells. The ICF is a big pool, twice the size of ECF so it can soak up a lot of water.
The ECF can be split into two compartments: intravascular fluid (IVF) and interstitial fluid (ISF), the so called third space. As the volume in the ECF decreases so does the intravascular volume (IVF) as the interface between IVF and ISF is highly permeable and a significant concentration does not develop at that interface. So as ECF volume drops the IVF volume also drops, blood pressure drops and the patient feels sick.
Now what if we carry out ultrafiltration (UF) during dialysis as well. That is what we normally do. It does not directly affect any concentrations significantly but it does decrease ECF volume very quickly. So now we have two competing processes decreasing intravascular volume.
My job (in Newcastle UK) was to try to work out how to use computer control of hemodialysis machines to minimize this effect and we looked at separate UF and hemodialysis (HD) and also haemodiafiltration (in Ulm, Germany). I came to the conclusion that the solute that was most important was not urea but sodium since it is confined to the ECF.
We needed to increase the dialysate sodium concentration which at the time was 134 and use UF to remove sodium.
Secondly I recommended varying the sodium concentration in the dialysate during dialysis to minimize the peak fluid shifts and derived equations to do that. I was funded in part by Fresenius and they patented the idea and built it into their dialysis machines as sodium modeling.
So now to the question. If we want to do UF separately from dialysis is it better to do it before or after HD? The disequilibrium problem reaches its peak near the beginning of HD and then drops off exponentially with time so it reaches a minimum at the end of HD. So if we minimize ultrafiltration during dialysis and remove volume by UF after completion of HD the competing fluid shifts caused by disequilibrium would be at their minimum and it should be better tolerated.
So that is the long answer to a simple question. I hope it is helpful.
Dr Duranti, I was interested in your comment about using ultrafiltration during the third dialysis treatment of the week. One of my proposals based on modeling was to use a longer dialysis treatment on the third day in preparation for the longer interdialysis interval over the weekend. So on a Monday-Wednesday-Friday schedule you would do a longer dialysis on Friday. This would avoid fluid and toxin overload during the weekend. We simply called it Short-Short-Long or SSL dialysis. I was working with Dr Goggin in Kent, UK at the time and he studied it successfully in a group of patients. Some people thought it was too difficult to do different scheduling on different days of the week although that wouldn't be a problem for home dialysis. You could even do UF for an additional hour every Friday and not other days of the week on a routine basis as you implied.
Dear Dr Lewis, I read with care of your program concerning a longer dialysis treatment in the last seance of the week. There is no doubt that this could improve the general condition of the patient during the longer time without dialysis, but this ,I think, concerns only the metabolic aspect of the patent ,including, may be acid base balance, even if problematic to induce a light alkalosis to prevent a possible future acidosis . But, the fundamental problem in the greatest part of patents is the risk of a greater gain of the weight along the two days without treatment. Because its impossible to perform a significant greater loss of water beyond the correct one's dry weight, each h patent has to control his/herself water input as usual, to avoid the dangerous excessive increasing in weight.
In other words you confirm my answer that isolated ultrafiltration is better at the end of Hd because starting with ultrafiltration and continuing with Hd can induce volume shifts between intra and extracellular space so that hypovolemia can induce markded hypotension and require fluid replacement , vanishing the precedent ultrafiltration .
Yes Dr Duranti, you already hit the nail on the head. I just added a bit of theory to substantiate it. I think it would be interesting to do a bit more work on this. A lot depends on how sodium is removed. It seems to me that we could minimize fluid shifts by minimizing the amount of sodium removed by dialysis and instead removing it by filtration either during dialysis or after.
If we want to reduce the diffusive losses to zero we would need to make the dialysate sodium concentration the same as the concentration in plasma water. We think of a normal plasma sodium concentration as 140 but if we correct for the protein concentration in plasma it is really 154 mmol/L in plasma water. That is exactly the same as normal saline and I am sure that is no coincidence!
If we used a dialysate concentration of 154 we would probably have difficulty removing enough sodium. We would need really high ultrafiltration rates which would tend to cause too much volume to be removed. In that case we can give a suitable replacement fluid back to the patient and we can regulate what solutes go back. That is the idea behind hemodiafiltration. Returning iv fluids adds to the expense.
Regarding Short-Short-Long dialysis Dr Ruggieri you are quite right. It occurred to me at the time that we may benefit from more solute removal before the long break and more volume removal after the long break, assuming the patient doesn't get too fluid overloaded during the long break. It isn't quite as straightforward as it seems. In the real world do we really get patients down to their ideal dry weight with every dialysis? If not, using the longer dialysis before a long break just increases our chances of getting the patient well dried out before the long break.
In conclusion isolated ultrafiltration is valid only if made isolated and not before or after Hd . If you want to remove fluids and clear blood , without hypotension , particularly in pts with high vascular instability , you have to recurr to HDF , AFB or HF . Do you agree ??
Hmmm... Well yes in principal if you are talking about a patient who cannot tolerate any fluid shifts perhaps you are right. But I don't think it is quite so simple in the real world. You are more likely to come across some patients who are not totally intolerant but are less tolerant than others and in those cases you may be able to modify the dialysis / filtration technique in some way to accommodate them.