CVVH and CHF fluid

[waterbottle10]

I'm a bit confused about this topic. I had a patient that was on CVVH due to acidosis/electrolyte derangements. However CVVH wasn't able to be performed due to technical difficulties.. and the machine was just ran with CHF fluid alone, and I was explained that using CHF fluid alone only removes volume, but doesn't fix electrolyte issues, so we have to get CVVH running asap to remove other stuff.

Can someone explain this to me? CVVH uses hydrostatic pressure i thought. Not sure how CHF fluid alone can remove volume, and only volume..?

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[jdh71]

Maybe there is some technical lingo nuance here but what are your acronyms standing for here?

CHF = convention hemofiltration??

 

[Raryn]

I think what he means is that they had a machine that could do ultrafiltration (like people used to do for CHF before it was shown to be useless/equivalent to lasix) but not actual CVVH. Simple ultrafiltration is slower and only removes fluid but not solutes. Both are modes of CRRT. I'm not sure of the difference in the technical specifications of the machines. Do we have any nephrologists around?

 

[jdh71]

I think what he means is that they had a machine that could do ultrafiltration (like people used to do for CHF before it was shown to be useless/equivalent to lasix) but not actual CVVH. Simple ultrafiltration is slower and only removes fluid but not solutes. Both are modes of CRRT. I'm not sure of the difference in the technical specifications of the machines. Do we have any nephrologists around?

I've never heard of ultrafiltration referred to as "CHF".

It's all pretty much bull**** when it comes to treating congestive heart failure though. If you can't get the fluid off by conventional means and they aren't a transplant candidate they need a palliative/hospice consult not a request to renal to do something that has been shown not to ultimately be helpful.

 

[waterbottle10]

Maybe there is some technical lingo nuance here but what are your acronyms standing for here?

CHF = convention hemofiltration??

I believe continuous hemofiltration

I think what he means is that they had a machine that could do ultrafiltration (like people used to do for CHF before it was shown to be useless/equivalent to lasix) but not actual CVVH. Simple ultrafiltration is slower and only removes fluid but not solutes. Both are modes of CRRT. I'm not sure of the difference in the technical specifications of the machines. Do we have any nephrologists around?

Simple ultrafiltration? What is that. If only fluids are removed but not filtrates, wont it just concentrate the blood, making things worse in electrolyte derangements/acidosis?

 

[Raryn]

I believe continuous hemofiltration



Simple ultrafiltration? What is that. If only fluids are removed but not filtrates, wont it just concentrate the blood, making things worse in electrolyte derangements/acidosis?

(Per google), apparently the appropriate name is "Slow Continuous Ultrafiltration" or SCUF. It takes plasma/water off but doesn't use a dialysate or anything so it doesn't change the concentration of electrolytes in the remaining plasma. As opposed to CVVH which also fixes the stuff you're putting back into the patient.

 

[thehundredthone]

I'm a bit confused about this topic. I had a patient that was on CVVH due to acidosis/electrolyte derangements. However CVVH wasn't able to be performed due to technical difficulties.. and the machine was just ran with CHF fluid alone, and I was explained that using CHF fluid alone only removes volume, but doesn't fix electrolyte issues, so we have to get CVVH running asap to remove other stuff.

Can someone explain this to me? CVVH uses hydrostatic pressure i thought. Not sure how CHF fluid alone can remove volume, and only volume..?

CHF (as it's used in this context) and CVVH are really the same thing, CVVH being a form of CHF with CAVH being the other form. The only principle in use is convection (high flow).

Once you add diffusion (and countercurrent dialysate) to the mix, it becomes CVVHDF (hemo-dia-filtration). And I wonder if this is what they might have meant by adding CVVH fluid - that they wanted to add a dialysate?

Simple ultrafiltration? What is that. If only fluids are removed but not filtrates, wont it just concentrate the blood, making things worse in electrolyte derangements/acidosis?

SCUF has a low rate of ultrafiltration so the solutes don't get as much time to move across the membrane, hence more water is taken off than solute. And yes, it is not very useful in the setting of acidosis. In fact, theoretically at least, in severe hyperkalemia IHD/SLED can be more useful than any CRRT because of higher efficiency of LMW solute removal.

 

[waterbottle10]

I see, thanks, very complicated topic for my simple mind.. I will have to read more about SCUF... and all these filtration mechanisms

 

[jdh71]

Now. ITT. Dorks.

 

[thehundredthone]

Now. ITT. Dorks.

You were the only one in the thread when you posted that?

Btw this guy doesn't like you. What better way to open a chapter than by saying "Why should we wait for the results of clinical trials to provide evidence when CHF patients need obvious water and sodium depletion?"

I see, thanks, very complicated topic for my simple mind.. I will have to read more about SCUF... and all these filtration mechanisms

If there's one thing to take away from this thread it's that we're all dorks there's no role for "taking off volume" by dialysis in acidosis.

 

[jdh71]

You were the only one in the thread when you posted that?

Btw this guy doesn't like you. What better way to open a chapter than by saying "Why should we wait for the results of clinical trials to provide evidence when CHF patients need obvious water and sodium depletion?"


If there's one thing to take away from this thread it's that we're all dorks there's no role for "taking off volume" by dialysis in acidosis.

Are you mad?

 

[Raryn]

Btw this guy doesn't like you. What better way to open a chapter than by saying "Why should we wait for the results of clinical trials to provide evidence when CHF patients need obvious water and sodium depletion?"

Maybe because when they did the randomized controlled trial it was shown to not be any better than loop diuretics?

 

[jdh71]

Maybe because when they did the randomized controlled trial it was shown to not be any better than loop diuretics?

Also. ITT. Someone who is mad.

 

[thehundredthone]

Are you mad?

What about? Or do you mean mad in the insane way.

Maybe because when they did the randomized controlled trial it was shown to not be any better than loop diuretics?

I would be pedantic and talk about studies looking at SCUF as an option in diuretic resistant patients, but maybe you didn't get my amusement at a man who says "Why should we wait for the results of clinical trials to provide evidence" while basing his info on selected trials that support his stance. You realize I didn't even talk about heart failure in any of my posts. @jdh71 brought it into this thread and I'm pretty much on board with what he said.

ITT. People not having the best day with reading.

 

[jdh71]

To be fair. Reading is hard.

 

[instatewaiter2]

I've never heard of ultrafiltration referred to as "CHF".

It's all pretty much bull**** when it comes to treating congestive heart failure though. If you can't get the fluid off by conventional means and they aren't a transplant candidate they need a palliative/hospice consult not a request to renal to do something that has been shown not to ultimately be helpful.

For run of the mill volume overload, I completely agree. However, in certain circumstances it is helpful. For a patient who is very tenuous with renal function that is worsening, if you try to push them too hard with diuretics, you will push them over the edge and never revive their kidneys.

For those with severely decompensated HF, they have a combination of poor forward flow and bad renovascular congestion. The combination creates a bad transglomerular pressure. Afterload reducing it worsens this and yyou don't have the renal perfusion to diurese them. These patients respond well to UF. You reduce the CVP, you can then use diuretics and afterload reduction and keep them chugging along for a few more months. But I agree, it is so sparingly needed that perhaps 1 in 100 HF admissions would benefit. Usually a little diuresis and little afterload reduction is all you need

 

[jdh71]

For run of the mill volume overload, I completely agree. However, in certain circumstances it is helpful. For a patient who is very tenuous with renal function that is worsening, if you try to push them too hard with diuretics, you will push them over the edge and never revive their kidneys.

For those with severely decompensated HF, they have a combination of poor forward flow and bad renovascular congestion. The combination creates a bad transglomerular pressure. Afterload reducing it worsens this and yyou don't have the renal perfusion to diurese them. These patients respond well to UF. You reduce the CVP, you can then use diuretics and afterload reduction and keep them chugging along for a few more months. But I agree, it is so sparingly needed that perhaps 1 in 100 HF admissions would benefit. Usually a little diuresis and little afterload reduction is all you need

I promise I don't need any pathophysiology lectures.

CVP is bull****. Might as well have a random number generator for what it can tell you.

 

[instatewaiter2]

I promise I don't need any pathophysiology lectures.

CVP is bull****. Might as well have a random number generator for what it can tell you.

yeah wasn't really meant for you. In the studies, right atrial pressure (which usually is reasonably estimated by CVP) was the most closely correlated to worsening of renal function in those with decompensated HF.

 

[Raryn]

For run of the mill volume overload, I completely agree. However, in certain circumstances it is helpful. For a patient who is very tenuous with renal function that is worsening, if you try to push them too hard with diuretics, you will push them over the edge and never revive their kidneys.

For those with severely decompensated HF, they have a combination of poor forward flow and bad renovascular congestion. The combination creates a bad transglomerular pressure. Afterload reducing it worsens this and yyou don't have the renal perfusion to diurese them. These patients respond well to UF. You reduce the CVP, you can then use diuretics and afterload reduction and keep them chugging along for a few more months. But I agree, it is so sparingly needed that perhaps 1 in 100 HF admissions would benefit. Usually a little diuresis and little afterload reduction is all you need

*shrug*. I've yet to see a patient where we had to resort to UF to compensate their HF. Occasionally one will require a short term inotrope to help maintain, but assuming they're not ESRD, diuretics will get you there eventually.

 

[IMreshopeful]

*shrug*. I've yet to see a patient where we had to resort to UF to compensate their HF. Occasionally one will require a short term inotrope to help maintain, but assuming they're not ESRD, diuretics will get you there eventually.

Ditto, I've actually had numerous patients unable to tolerate UF and actually ended up hastening renal failure by initiating UF earlier than adequate. Obviously generally it is a bad idea in people with functioning kidneys.