Hi, so my good friend Jeff Scott, ED/ICU doc and serious POCUSologist, asked me to summarize our current approach to fluid management, which is an amalgam of literature, physiology and bedside medicine-based evidence.
A few points to emphasize:
- does my patient need fluid/ will he/she benefit from fluid.
- is my patient fluid tolerant
- is my patient fluid responsive – yes, it’s the last and least important
I figure we may follow this up with a discussion – that’s often the best way to get to the real clinical decision points, and it’s always interesting to hear the questions and ideas that come up, so looking forward to it!
I figured might as well make a mini podcast of it, so here it is:
So the discussions go on about volume status and POCUS, and recently one in particular made me realize that it is important to reframe the way we think about “volume status.” As Segun Olusanya (better known as @iceman_ex) said, “the IVC is not a fuel tank indicator,” and indeed it is not. But even if it was, would that be useful? If somehow, an 18 mm IVC (short axis circular or average of course!) corresponded exactly to a 0.70 ml/kg blood volume, would that be of any use?
No. Of course not.
I get asked this question in consult a lot. So I could be a stickler on principle and answer, whether verbally or in a consult, that the volume status cannot be precisely ascertained using POCUS, and keep walking down the hospital hallway.
But let’s instead reconsider the true clinical question for a moment. What does “volume status” mean when requested by a colleague. The truth is that he or she is likely asking you whether there is a need to give fluid, remove fluid, or stay the course.
Ahhhh. Now POCUS, the IVC and its friends can help. A lot. A lot more that most clinical examinations and chart reviews of weights or ins and outs can. Way more. Why? Because if you are cool, with a normodynamic heart and a small IVC, you are on the low side of volume. Now you may also have a lot of B lines from your pneumonia and the lack of volume tolerance will give your answer to be very careful with fluids. If you are warm and hyperdynamic with a small IVC and totally clear lungs, no elevated ICP and a soft belly, you may just be vasodilated but, if your BP is on the low side, some fluid is a fair go, so long as you follow closely thereafter for fluid stop points. If you have a low urine output, a big IVC, a pulsatile PV and a poor LV, you probably need lasix, no matter how clear your lungs are and even if your creatinine is rising, in fact, especially since it is rising.
The permutations are myriad. But that’s why we have MDs and are supposed to be able to integrate bits and pieces of physiological data to come up with an understanding of our patients. And POCUS gives us an unprecedented bedside view into this physiology.
So if you do have legit POCUS skills, and are able to do a bit more than a long axis M mode of the IVC, then try this instead:
“Sure thing, now tell me a bit about your patient – I imagine you’re debating whether to give some fluids or diurese?”
Forget about volume status in terms of absolutes. Just think of what the clinical question is, and give your colleagues the answers they need.
I think the patients will do a lot better that way.
I’ve already put up a lot of stuff about the IVC here over the years.
(original figure from this old post)
So Rory (@EMnerd) hit us last week with an interesting question that was brought up by David Gordon, a resus fellow working with him, and thought some of us may be willing to belabour his point. A lengthy and really fascinating exchange ensued, which I felt was worth sharing with the #FOAMed community:
Rory (Spiegel @EMnerd) find him on emcrit.org
Korbin Haycock (please leave comments to encourage him to get on Twitter)
Segun (Olusanya @iceman_ex) find him on LITFL.com and The Bottom Line
Me (@ThinkingCC) also thinkingcriticalcare.com
My editorial comments!
David brought up an interesting question today. Why not do a straight leg raise and use TAPSE to assess the likelihood the pt will be “volume responsive”?
Lets say we use Korbin’s gold standard I think we still have to ask what is the benefits of giving this pt fluids? There are many patients I see who would meet all the criteria outlined by Korbin in whom I still don’t administer fluids because whatever increase in cardiac output I get will be transient at best. I am inclined to sit tight allow my antibiotics to take effect and let the pt correct their own vasoplegia. After an initial small aliquot of fluid in the ED I like to see obvious signs of hypovolemia before I give additional boluses. I do like the CLASSIC trials criteria:
(1) Lactate of at least 4 mmol/L
(2) MAP below 50 mmHg in spite of the infusion of norepinephrine
(3) Mottling beyond the edge of the kneecap (mottling score greater than 2)
In my mind lactate in and of itself uninterruptible. In a pt who is otherwise improving and the lactate is not clearing as fast as I would like I tend to just stop checking it. The one I find troublesome is in the post resus pt who doesn’t look great, I don’t have an obvious source, their pressor requirements are slowly rising and the lactate is hovering in the 4-5 range. That’s the pt that tends to do poorly if you don’t identify and establish source control
How does the RV respond to a fluid bolus?
To answer this question first we must understand the role of the right heart in the circulatory system. Often the right ventricle (RV) is compared to the left ventricle, in reality it serves an entirely different function. The left ventricle generates the necessary pressures required to maintain systemic perfusion. The right ventricle’s job is to enable venous return, which is generated by the gradient between the mean systemic filling pressure and the right atrial pressure (RAP). The role of the RV is to maximize that gradient by keeping the RAP as low possible.
With this in mind let us examine the RV’s response to a fluid bolus. As the RV becomes filled, conformational changes occur within the RV that allow it to increase its stroke volume without increasing the distending pressure.Under normal circumstances, the RV end diastolic distending pressure does not increase in response to fluid loading. Therefore, if the RV is functioning appropriately, RAP does not accurately reflect RV preload. But in pathological states, when the RV is hypertrophied, diseased, or overdistended there is an inverse relationship between RVEDV and RV stroke volume. Any fluid, or increased RV pressure beyond this point results in an increase in RAP, decreasing venous return.1
1. Pinsky MR. The right ventricle: interaction with the pulmonary circulation. Critical care (London, England). 2016;20:266.
So that was the discussion. I certainly thought it was very interesting. Following this, we decided we’d band together and try to hammer out what we think should be the optimal management of shock, trying to tie in physiology, the scant evidence that is out there about resuscitation, and the pitfalls of venous congestion. Finding the sweet spot in the balance between vasopressors, inotropes and fluids is a very real challenge that all resuscitationists face regularly, and it is very unlikely that, given the complexity of such a protocol, looking at tolerance, responsiveness and perfusion, that an RCT would be done anytime soon.
We’ll be sure to share when we come to a consensus, but certainly the broad strokes can be seen here, and I’d love to hear anyone’s take on this!
And of course, we’ll definitely be discussing this further with smarter people at H&R2019 – think Jon-Emile Kenny (@heart_lung), Andre Denault and Sheldon Magder!
In Greek mythology, Prometheus (/prəˈmiːθiːəs/; Greek: Προμηθεύς, pronounced [promɛːtʰeús], meaning “forethought”) is a Titan, culture hero, and trickster figure who is credited with the creation of man from clay, and who defies the gods by stealing fire and giving it to humanity, an act that enabled progress and civilization. Prometheus is known for his intelligence and as a champion of mankind.
So, fresh from reading Jon’s post, I felt I had to add a bit of nuance in my previous post to what I feared some might extract as a take-home message, even if in fact, we are not that differing in opinion at all – which Jon expressed here:
i agree with ultrasound for finding the uncommon causes of shock. these examples seems to permeate twitter and make ultrasound very appealing. because ultrasound is non-invasive, it makes the risk-to-benefit ratio very low for these uncommon but highly-lethal and treatable causes.
but that needs to be compared to the risk-to-benefit ratio of ultrasound for the more common causes of shock – like ‘non-cardiogenic, septic’ etiologies as seen in SHOC-ED. here, “static’ ultrasound [as per the RUSH and ACES protocols] – per SHOC-ED – appears to be neither helpful nor harmful. your read of the discussion is perfect, but i was depressed because it read as if the authors only realized this ex post facto – study of previous monitoring utensils [e.g. PAC] should have pre-warned the authors …
i will take some mild issue with markers of volume responsiveness and tolerance. you are correct on both fronts – but what the data for the IVC reveals – perhaps paradoxically – is that true fluid responders can have a very wide-range of IVC sizes from small to large and unvarying … this was born out in most of the spontaneously breathing IVC papers [airpetian and more recent corl paper] the sensitivity was rather poor.
the same *could* be true for the opposite side of the coin. a large great vein may not mean a volume intolerant patient. i tried to exemplify how that could be so in the illustrative case in my post. an elderly man, with probable pulmonary hypertension and chronic TR who probably “lives” at high right-sided pressures. nevertheless, he likely has recurrent C. diff and is presenting 1. hypovolemic and 2. fluid responsive despite his high right-sided pressures. portal vein pulsatility *could* be quite high in this patient – but he still needed some volume.
the obvious underlying issue here – which I know you are well attuned to – is that a Bayesian approach is imperative. when you PoCUS your patients, you are inherently taking this into consideration – i know that you are a sophisticated sonographer. my hidden thesis of the post is that if ultrasound findings are followed in a clinical vacuum and followed without really understanding the physiology [which can explain clinico-sonographic dissociation – like the patient in my fictitious case]… disappointment awaits.
nice analogy – i think Korbin’s response is appropriate and i look forward to speaking alongside him in May. as i chew on the SHOC-ED a little and try to distill my concerns – i think what it boils down to is this: it’s less about playing with fire – i think – and more about how this fire is brought to the community as a whole. my post on pulmccm was more of a warning to the early adopters [like us] who are planning these trials. imagine 40 years ago:
-the flotation PAC is introduced, a small group of clinical physiologists use it thoughtfully, understand the caveats, the problems of data acquisition, interpretation, implementation, the problems with heart-lung interactions, intra-thoracic pressure, etc.
-these early adopters present their results to the community as a whole
-the physiology of the PAC is simplified
-the numbers from the PAC are introduced into algorithms and protocols and **widely** adopted into clinical practice
-the PAC is studied based on the above and found to make no difference in patient outcome.
-in 2010 a venerable intensivist suggests floating a PAC in a complicated patient and the fellow on rounds chuckles and states that their is ‘no evidence of benefit’
does this sound eerily familiar? is our present rhyming with the past? if the planners of POCUS trials are not careful, i promise you that the same will happen but insert any monitoring tool into the place of PAC. i can very easily visualize a fellow on rounds in the year 2030 scoffing at the idea of PoCUS because trials [SHOC-ED, and future trials x, y and z] showed no difference in patient outcome. is it because PoCUS is unhelpful or is it because the way it was introduced and studied was unhelpful? and the three of us will sound like the defenders of the PAC from 30 years ago: “PoCUS isn’t being used correctly, it’s over-simplified, it works in my hands, etc. etc.”
it’s not PoCUS that’s unhelpful, it’s how we’re implementing it – and i was most depressed when the authors of SHOC-ED appeared to stumble upon this only in the discussion of their paper – like you mentioned phil. imprecise protocols will result in equally imprecise data and the result will be nebulous trial outcomes. we should all be worried.
Excellent points Jon. The PAC example is very relevant, as on more than one occasion, I’ve had the argument put to me by some colleagues that essentially how I’m applying POCUS is really no different than the information gleaned from the PAC, and “that’s been shown to not be helpful to outcomes” etc. So, therefore, why do I bother?
Then again, I’ve seen a fair amount of phenylephrine being thrown at hypotensive cardiogenic shock patients after a 2 liter normal saline bolus didn’t do the trick.
You are absolutely spot on when you point out that seeing the big picture, knowing the physiology, and being aware of the pitfalls of isolated data points is important to making the right decisions in patient care.
Furthermore, I agree that when a clinical trial is done that doesn’t consider some of the nuances of all this, and “shows” that POCUS, or any other diagnostic modality for that matter, doesn’t contribute to better patient outcomes, it probably only serves to marginalize a potentially valuable diagnostic tool to an actually astute intelligent clinician.
I’m not meaning by saying this to bash the good intentions of the SHOC-ED trial. To be fair, it’s really hard to design a trial that can take into account all the permutations that are involved in any individual patient presents with, having their own unique clinical situations, hemodynamic profiles, co-morbidities (both known and undiagnosed), etc. POCUS, PAC, transpulmonary thermodilution, ECG, chest x-ray, CT scans, labs, physical exam–these are all merely tools that guide patient care. Albeit some are way more powerful than others. I can image various amounts of uproar if some of these traditional tools were subjected to clinical trials to prove their utility. The argument, if proven “useless” in a study for the oldest and well accepted tools would always be, “put it in the clinical context, and its value speaks for itself.” For me, I’d happily like to make clinical descisions based on information based on an advanced POCUS exam or PAC, rather than interpreting hepatojugular reflux or a supine chest x-ray.
Any diagnostic test requires that the clinician understand the limitations of that test, and understand that the whole clinical scenario must me taken into account. You’ve hit on that, I think, with your argument. This surely has implications when any technology or test is studied.
This event is past. It was awesome. If you really wish you’d been there, you can catch most of it here!
And don’t miss H&R2020!
Registration is open and we have said goodbye to the snail mail process. Fortunately, we are a lot more cutting edge in medicine than in non-medical technology.
We are really excited about this programme, and a lot of it comes from the energy and passion coming from the faculty, who are all really passionate about every topic we have come up with.
The hidden gem in this conference is the 4 x 40 minutes of meet the faculty time that is open to all. Personally I’ve always felt that I learn so much from the 5 minute discussions with these really awesome thinkers and innovators, so wanted to make it a priority that every participant should get to come up to someone and say ‘hey, I had this case, what would you have done?’ Don’t miss it!
CME Accreditation for 14 hours of Category 1.
This programme has benefitted from an unrestricted educational grant from the following sponsors (listed alphabetically):
The Accreditation is as follows:
Here is the Final Programme:
Wednesday May 22 – PreCongress course
- Full day Resuscitative TEE course
FOR DETAILS SEE HERE
2. Full day Keynotable
3. Half day Hospitalist POCUS (PM)
4. Half day Critical Care Procedures (AM)
5. Half day Brazilian Jiu-Jitsu for MDs (AM)
for more details on these pre-conference courses please see here.
Main Conference Programme: H&R2019 Full Pamphlet
Thursday May 23rd Meet the Faculty cocktail! 1900 – Location TBA – BOOKMARK THIS PAGE!
So I had the chance to catch my friend Josh today, and, as always, he had some unique insights to contribute.
I really like the IR idea from the standpoint of objectivity and reproducibility. At first it sounded like a fancy (and fun, of course) way to check skin temperature as I routinely do, but the ability to objectify from doc to doc could be really interesting. Will get on that with my colleagues in my unit. We’ll see what we can come up with in the next months!
Love to hear from some others trying to tweak and optimize their resus!