Beclometasone
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Hey guys,

I was wondering if I can pick the brains of anyone here who is Renal/anaesthetics/GenMed/ITU.

I am an F2 in a general medical/AMU ward, and I often get AKI/CKD/heart failure patients with sepsis/infections etc where I need to think about giving fluids. My consultant often asks the nursing staff to keep an accurate fluid balance and measure urine output, or do daily weights etc. (I know they're a pain to do, and are rarely done accurately). I have a few questions regarding the theory behind why we do this in a general medical/AMU context (I know ICU have their own fancy things - but I'm not directly interested in this). Any help much appreciated!!

1) I've seen a few 'fluid balance' charts. The main thing seems to be a row recording all the 'fluid IN' and another row with all the 'fluid OUT'. I understand the difference between IN and OUT is the NET change. But this still doesn't tell us the 'total fluid BALANCE'.
Surely we are missing an important piece of information - i.e. the initial fluid amount? (initial fluid balance + net change = final fluid balance).
The fluid chart tells us the net change, but how do you know the initial fluid status? Is this by clinical examination? But if you are using a clinical exam to estimate initial fluid status, then why not just do that every time you wanted to know the fluid status of a patient? (rather than messing around with input/output calculations?)

Spoiler:
Show

Monitoring urine output seems reasonable (as an indirect measure of renal perfusion in AKI/CKD patients). But if the patient is not getting enough fluid, urine output will fall. And if fluid overloaded, then it will show up on clinical examination (basal crackles, puffy ankles, SOB, CXR changes etc etc). Why bother with this fluid balance malarkey?



2) Some guidelines tell me to ‘set daily targets for fluid balance’ in these AKI/CKD/HF patients who are unwell. What target!?? Surely if there is evidence of fluid depletion, I need to give more fluids, and vice-versa until they are euvolemic. What's this concept of target?

Spoiler:
Show

I've been reading that in the acute phase, one needs to aim for positive fluid balance, but then aim for a neutral or negative fluid balance afterwards - because hypervolemia is associated with poorer outcomes etc etc. All well and good in theory, but I have yet to find specific numerical 'targets'. Can anyone give me ballpark figures to use for AKI on CKD patients/ patients with overloaded HF etc? Also, it would be pretty ballsy of me to aim for negative fluid balance in someone who originally came in with hypovolemic AKI surely?


3) Measuring Daily weights in cardiac failure. My issue with this is similar to fluid balance. You often won't know a patient's dry weight (e.g. it's the first time they're presenting with decompensated HF). So if a patient with overloaded HF is commenced on IV furosemide, here's what happens:
They lose a lot of weight in the first few days, and the weight loss slowly tapers off. This could either be due to (a) the fact they are plateauing as they approach their usual dry weight, or (b) the effectiveness of the diuretic therapy is falling (and they're still miles away from their dry weight). But if you don't know their original dry weight....surely it makes the entire exercise pointless? Therefore, daily weight not worth doing surely?


4) Bit of an unrelated question this one. I often start fluid overloaded HF patients on IV furosemide, and they end up developing low Na+ and K+ over a few days. I'm not sure how to treat these electrolyte abnormalities, especially because IV fluids are often avoided.
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With K+, I can always use Sando-K I guess. Not sure about low Na+ though - I usually give 0.9% NaCl, but obviously I can't in someone with recovering from decompensated HF.
Last edited by Beclometasone; 7 months ago
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Shivscape
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1) you sometimes need to know fluid balance to know how much IV fluid to replace: e.g high output stomas, diarrhoes/vomiting. Clinical examination is often unreliable. especially in young and fit patients who can compensate at the even /- 2 litres ofextracellular fluid2_ yes give positive FB in pre-renal AKI however once euvolaemic no benefit to giving more fluid, creatining comes down however if they continue to recieve excess IV fluid post euvolaemia then they might get pulmonary oedema and respiratory distress. I have seen this in post-op hypovolaemia several times.3) true: however patients will often have their regular weights documented by the cardiac failure nurses etc anyway so you may have a reference, also bear in mind that you aim for 0.5-1kg/day at most of weight reduction in most patients (unless severe overload), for this checking daily weights is the most accurate method: even more so than fluid balance on a general medical/surgical ward as with a 1:8 nurseatient ratio some things get missed4)for low K can add in spironolactone (has survival benefit in stage 3/4 CCF anyway) or amiloride. For low NA you can give slow sodium tablets, or can sometimes use urea tablets too. ALso sometimes you have to just accept the sodium will drop a bit more before it improves with diuresisAnyway thats my 2 cents
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nexttime
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(Original post by Beclometasone)
1) I've seen a few 'fluid balance' charts. The main thing seems to be a row recording all the 'fluid IN' and another row with all the 'fluid OUT'. I understand the difference between IN and OUT is the NET change. But this still doesn't tell us the 'total fluid BALANCE'.
Surely we are missing an important piece of information - i.e. the initial fluid amount? (initial fluid balance + net change = final fluid balance).
The fluid chart tells us the net change, but how do you know the initial fluid status? Is this by clinical examination? But if you are using a clinical exam to estimate initial fluid status, then why not just do that every time you wanted to know the fluid status of a patient? (rather than messing around with input/output calculations?)

Spoiler:
Show

Monitoring urine output seems reasonable (as an indirect measure of renal perfusion in AKI/CKD patients). But if the patient is not getting enough fluid, urine output will fall. And if fluid overloaded, then it will show up on clinical examination (basal crackles, puffy ankles, SOB, CXR changes etc etc). Why bother with this fluid balance malarkey?
Urine output is probably what they are mainly after. But if someone is losing a lot of fluid from say a stoma, you will want to know that your 3L daily IVI is more than their 5L lost via stoma or not, right?

In heart failure or bad CKD a positive fluid balance will show overload before clinical signs. Like almost all clinical examination, clinical signs are also variably accurate - these patients will almost always have at least some peripheral oedema right? Is it more or less today, when you weren't the one to examine them yesterday? How long have their legs been up? What time of day are you examining? Have they just taken off their TEDs? Etc.

2) Some guidelines tell me to ‘set daily targets for fluid balance’ in these AKI/CKD/HF patients who are unwell. What target!?? Surely if there is evidence of fluid depletion, I need to give more fluids, and vice-versa until they are euvolemic. What's this concept of target?

I've been reading that in the acute phase, one needs to aim for positive fluid balance, but then aim for a neutral or negative fluid balance afterwards - because hypervolemia is associated with poorer outcomes etc etc. All well and good in theory, but I have yet to find specific numerical 'targets'. Can anyone give me ballpark figures to use for AKI on CKD patients/ patients with overloaded HF etc? Also, it would be pretty ballsy of me to aim for negative fluid balance in someone who originally came in with hypovolemic AKI surely?
I've not seen specific fluid balance targets given in this way either. Doing so would kind of assume that the patient is getting reviewed multiple times per day and adjusting fluids to the 'target', when in reality you review them once, prescribe 24 hours of fluid and review again tomorrow, at which point any 'target' would be subject to change and review!

I'm not sure how you've interpreted this to mean giving hypovolemic patients fluid restriction. That mantra is more for your sepsis-induced AKI, pancreatitis, ITU-level sick patients, etc. A simple hypovolemic patient who has simply been corrected back to normal, clearly does not need re-depleting again

3) Measuring Daily weights in cardiac failure. My issue with this is similar to fluid balance. You often won't know a patient's dry weight (e.g. it's the first time they're presenting with decompensated HF). So if a patient with overloaded HF is commenced on IV furosemide, here's what happens:
They lose a lot of weight in the first few days, and the weight loss slowly tapers off. This could either be due to (a) the fact they are plateauing as they approach their usual dry weight, or (b) the effectiveness of the diuretic therapy is falling (and they're still miles away from their dry weight). But if you don't know their original dry weight....surely it makes the entire exercise pointless? Therefore, daily weight not worth doing surely?
What if their weight doesn't decrease? What if their weight decreases by 5kg in the first day? Would that change your plan at all?

4) Bit of an unrelated question this one. I often start fluid overloaded HF patients on IV furosemide, and they end up developing low Na+ and K+ over a few days. I'm not sure how to treat these electrolyte abnormalities, especially because IV fluids are often avoided.

With K+, I can always use Sando-K I guess. Not sure about low Na+ though - I usually give 0.9% NaCl, but obviously I can't in someone with recovering from decompensated HF.

Spiro is better than using some of their precious daily fluid allowance on disgusting sando-K!

Normally just tolerate low sodiums tbh unless it gets really really low.
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Beclometasone
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(Original post by Shivscape)
1) you sometimes need to know fluid balance to know how much IV fluid to replace: e.g high output stomas, diarrhoes/vomiting. Clinical examination is often unreliable. especially in young and fit patients who can compensate at the even /- 2 litres ofextracellular fluid2_ yes give positive FB in pre-renal AKI however once euvolaemic no benefit to giving more fluid, creatining comes down however if they continue to recieve excess IV fluid post euvolaemia then they might get pulmonary oedema and respiratory distress. I have seen this in post-op hypovolaemia several times.3) true: however patients will often have their regular weights documented by the cardiac failure nurses etc anyway so you may have a reference, also bear in mind that you aim for 0.5-1kg/day at most of weight reduction in most patients (unless severe overload), for this checking daily weights is the most accurate method: even more so than fluid balance on a general medical/surgical ward as with a 1:8 nurseatient ratio some things get missed4)for low K can add in spironolactone (has survival benefit in stage 3/4 CCF anyway) or amiloride. For low NA you can give slow sodium tablets, or can sometimes use urea tablets too. ALso sometimes you have to just accept the sodium will drop a bit more before it improves with diuresisAnyway thats my 2 cents
Thanks so much for this, it's gold! I see your point about daily weight; I guess if fluid balance was done perfectly there would be no need for daily weight (because you know 1L of fluid approx equals 1kg), so it's a useful fallback. I didn't know about Na+ tablets either, thanks.
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Beclometasone
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(Original post by nexttime)
Urine output is probably what they are mainly after. But if someone is losing a lot of fluid from say a stoma, you will want to know that your 3L daily IVI is more than their 5L lost via stoma or not, right?

In heart failure or bad CKD a positive fluid balance will show overload before clinical signs. Like almost all clinical examination, clinical signs are also variably accurate - these patients will almost always have at least some peripheral oedema right? Is it more or less today, when you weren't the one to examine them yesterday? How long have their legs been up? What time of day are you examining? Have they just taken off their TEDs? Etc.



I've not seen specific fluid balance targets given in this way either. Doing so would kind of assume that the patient is getting reviewed multiple times per day and adjusting fluids to the 'target', when in reality you review them once, prescribe 24 hours of fluid and review again tomorrow, at which point any 'target' would be subject to change and review!

I'm not sure how you've interpreted this to mean giving hypovolemic patients fluid restriction. That mantra is more for your sepsis-induced AKI, pancreatitis, ITU-level sick patients, etc. A simple hypovolemic patient who has simply been corrected back to normal, clearly does not need re-depleting again



What if their weight doesn't decrease? What if their weight decreases by 5kg in the first day? Would that change your plan at all?




Spiro is better than using some of their precious daily fluid allowance on disgusting sando-K!

Normally just tolerate low sodiums tbh unless it gets really really low.
PRSOM, thanks for this thorough reply!! I've been having a long think about what you said, especially about the stoma.

Soo if I'm understanding all this correctly.... fluid balance is not the same as hypo/euvo/hypervolemia. A negative fluid balance just means that in the last 24 hours, output is greater than input. The patient can have negative fluid balance but still be hypervolemic/fluid overloaded (e.g. when you're deloading a congested HF patient). Is this right?

Regarding the stoma example you used - so for example, in a CKD patient admitted with high stoma output, diarrhoea and vomiting etc, but is euvolemic, then fluid balance is the right thing to do because it helps you keep the patient euvolemic despite losses from multiple sites ( by allowing you to judge how much fluid to give).

But say you have a CKD patient who is 'slightly' fluid overloaded (his ankles are 'a bit' puffy, there is 'some' pulmonary congestion on CXR, and his Sats are slightly low at 94% etc) who came in with pneumonia etc. Obviously, I would have to aim for a slight negative fluid balance to make sure he/she returns to euvolemia. But how do I come up with a sensible target? Is -200ml/24hrs good? why not -500 or -1000/24hrs ? How do I convert the clinical signs into fluid balance targets?

Sorry for all the questions! But thanks for your help so far
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nexttime
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(Original post by Beclometasone)
PRSOM, thanks for this thorough reply!! I've been having a long think about what you said, especially about the stoma.

Soo if I'm understanding all this correctly.... fluid balance is not the same as hypo/euvo/hypervolemia. A negative fluid balance just means that in the last 24 hours, output is greater than input. The patient can have negative fluid balance but still be hypervolemic/fluid overloaded (e.g. when you're deloading a congested HF patient). Is this right?
Yes definitely.

To just assess how dehydrated someone is its just the fluid status exam - hopefully something med school taught you!

Regarding the stoma example you used - so for example, in a CKD patient admitted with high stoma output, diarrhoea and vomiting etc, but is euvolemic, then fluid balance is the right thing to do because it helps you keep the patient euvolemic despite losses from multiple sites ( by allowing you to judge how much fluid to give).
Sure, although they're unlikely to pitch up euvolemic in such a scenario. You'd have to make that assessment on arrival.

But say you have a CKD patient who is 'slightly' fluid overloaded (his ankles are 'a bit' puffy, there is 'some' pulmonary congestion on CXR, and his Sats are slightly low at 94% etc) who came in with pneumonia etc. Obviously, I would have to aim for a slight negative fluid balance to make sure he/she returns to euvolemia. But how do I come up with a sensible target? Is -200ml/24hrs good? why not -500 or -1000/24hrs ? How do I convert the clinical signs into fluid balance targets?

Trial and error in all honesty. No patient is the same, and even for the same patient, the scenario can change.

NICE has some fluid balance guidelines, which I'm pretty sure 80% of doctors don't know exists and I've certainly never actually seen used. It tried to make the whole process quantified (hence, much more complicated) but fundamentally still relies on very subjective measures and assessments. For example, it expects you to assess whether a patient is 5%, 10%, 15%, or 20% dehydrated (or something like that) by examination.

In reality, you think someone is say dehydrated, you guess by how much, and you try to correct it, then a set period later (usually next day, but in someone very unwell might only be a few hours later) you reassess, see if its helped, re-examine, decide what to do next. Clearly, things like creatinine, urine output etc, can be very useful in this. In people with things like CCF and AKI, this can be really tricky. Giving furosemide can actually resolve an AKI in this group. Consultant cardiologists get this wrong all the time.

Its of note that rehydration does not always have to be parental. Using oral hydration is better - less electrolyte abnormalities, less cannula infections etc. In the developing world, its normal and highly successful to treat cholera with just oral rehydration salts and fluid balance. We're talking 20 litres of diarrhoea and commensurate fluid replacement here. Whereas we'll just give a slow litre overnight to rehydrate an older person right?

NG fluid is probably underused too.
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Beclometasone
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(Original post by nexttime)
Yes definitely.

To just assess how dehydrated someone is its just the fluid status exam - hopefully something med school taught you!



Sure, although they're unlikely to pitch up euvolemic in such a scenario. You'd have to make that assessment on arrival.




Trial and error in all honesty. No patient is the same, and even for the same patient, the scenario can change.

NICE has some fluid balance guidelines, which I'm pretty sure 80% of doctors don't know exists and I've certainly never actually seen used. It tried to make the whole process quantified (hence, much more complicated) but fundamentally still relies on very subjective measures and assessments. For example, it expects you to assess whether a patient is 5%, 10%, 15%, or 20% dehydrated (or something like that) by examination.

In reality, you think someone is say dehydrated, you guess by how much, and you try to correct it, then a set period later (usually next day, but in someone very unwell might only be a few hours later) you reassess, see if its helped, re-examine, decide what to do next. Clearly, things like creatinine, urine output etc, can be very useful in this. In people with things like CCF and AKI, this can be really tricky. Giving furosemide can actually resolve an AKI in this group. Consultant cardiologists get this wrong all the time.

Its of note that rehydration does not always have to be parental. Using oral hydration is better - less electrolyte abnormalities, less cannula infections etc. In the developing world, its normal and highly successful to treat cholera with just oral rehydration salts and fluid balance. We're talking 20 litres of diarrhoea and commensurate fluid replacement here. Whereas we'll just give a slow litre overnight to rehydrate an older person right?

NG fluid is probably underused too.
Thank you so much - it all fits together in my mind now! (didn't know about those NICE guidelines; I guess it must be pretty hard telling the difference between 10% and 15% etc though)
Yes, the CCF+AKI game where we make alternate bets on fluid/furosemide challenges is sadly well known to me
Really appreciate your response - thanks again.
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(Original post by Beclometasone)
Thank you so much - it all fits together in my mind now! (didn't know about those NICE guidelines; I guess it must be pretty hard telling the difference between 10% and 15% etc though)
Give them a read maybe they will seem more... implement - able... to you.
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