Transcript
Speaker: Welcome to Critical Matters, a SOUND podcast covering a broad range of topics related to the practice of intensive care medicine.
Speaker: SOUND provides comprehensive critical care programs to hospitals across the country.
Speaker: To learn more about our programs and career opportunities, visit www.soundphysicians.com.
Speaker: And now your host, Dr. Sergio Zanotti.
Speaker: In patients with acute circulatory failure or shock
Speaker: Fluid administration is a cornerstone of therapy.
Speaker: However, the decision to give fluids or not should not be taken lightly.
Speaker: The risk of under or over-resuscitating a patient are both associated with poor outcomes.
Speaker: Furthermore, the therapeutic window for fluids is narrow.
Speaker: In today's episode of the podcast, we will discuss prediction of fluid responsiveness.
Speaker: Our guest is Dr. Haney Malamud.
Speaker: Dr. Malamud is a critical care intensivist and emergency medicine clinician at Cooper University Health
Speaker: He is also associate professor of medicine and of emergency medicine at Cooper Medical School of Rowan University in Camden, New Jersey.
Speaker: Haney is a great bedside clinician, an ultrasound guru, and a master educator.
Speaker: He is the editor-in-chief of Critical Care Now, an amazing educational platform for critical care, and he's also the founder of ResusX, a conference focusing on state-of-the-art resuscitation.
Speaker: I encourage you to check and explore both of those as they provide an enormous amount of resources
Speaker: for critical care clinicians.
Speaker: Hany, welcome back to Critical Matters.
Speaker: Sergio, so good to be back.
Speaker: Thanks for having me.
Speaker: So today we're going to answer the always present question in every single clinical shift that we do, which is, should I give more fluids or not, right?
Speaker: Should I stay or should I leave?
Speaker: Right.
Speaker: No, I mean, it's amazing, Sergio.
Speaker: We can do these amazing diagnostic imaging.
Speaker: We can do robotic surgery across an ocean.
Speaker: and yet we can't figure out how much fluid to give our patients.
Speaker: So it always gives me pause and a little bit of a chuckle to think about this topic.
Speaker: Man, this is a topic that obviously is very closely related to ultrasound, but it's also something that as somebody who really focuses not only on critical care, but also in the initial phase of resuscitation, you've been very, very interested in and have explored deeply.
Speaker: So I'm happy to have you today to answer all our questions and give us kind of
Speaker: the state of the art or the most current update of where we stand and this kind of ever-ending quest, right, to answer that simple question sometimes, should I give more fluids or not?
Speaker: Hany, I would like to start with physiology and maybe just with very basic physiology, if you're just going to give us kind of another view of how you frame physiology and thinking about this topic.
Speaker: Yeah, so the one thing that I try to keep in mind and I try to impart
Speaker: to my learners is the only single reason that we want to give fluids for patients is to increase the stroke volume.
Speaker: There really is no other reason to give a fluid bolus as we know it.
Speaker: And this is a concept brought by Dario Mastarini, who is the Italian physiologist who kind of came up with this concept or discovered it in frog muscles.
Speaker: And essentially, you want to stretch the muscle fibers in the heart to an optimal length to improve cardiac outputs.
Speaker: If you're already optimized, then there should be no other reason to give volume for people.
Speaker: And then Frank and Starling poached that idea and came up with the Frank-Starling curve that we all know and love from medical school.
Speaker: And when you think of stroke volume, it depends on preload, afterload, and contractility, right?
Speaker: So really when we talk about fluids, ultimately what we're really, really affecting is one of those factors, which is like you said, the preload or the stretch.
Speaker: And I think that sometimes people forget that.
Speaker: On one hand, what are you trying to achieve, but also what can you achieve?
Speaker: And I believe that what you also were mentioning is that the fact that you can increase stroke volume by giving fluid doesn't always mean that you should give fluid.
Speaker: I probably would be following that category right now.
Speaker: Yeah, exactly.
Speaker: I mean, if you take any one of us right now and you did some of the things that we'll talk about later in the podcast, you would find that we are fluid responsive.
Speaker: But does that mean that we need volume at that moment?
Speaker: And that's what adds complexities to this discussion.
Speaker: And then, as you mentioned, you know, we we think about fluid as being everything, right?
Speaker: It just increases cardiac output, but cardiac output is dependent on so many things.
Speaker: And if you take something like sepsis, for example, there are people out there who
Speaker: believe that you probably shouldn't give the amount of fluid that's even recommended that we're giving for people because sepsis is a vasodilatory process, it's not a volume process.
Speaker: So inherent in this question of fluids comes all the other aspects that we should be mindful of when we're asking the question, does this patient need volume?
Speaker: And on a very basic level, obviously the positive effect of giving volume at the appropriate time, like you said, is that it would increase stroke volume, which ultimately increases cardiac output.
Speaker: which ultimately improves oxygen delivery to the tissues.
Speaker: Could you also talk about the other side of that coin, which is something that I'm a little bit older, have more gray hair than you do, but I still remember, Haney, when I was at the bedside learning, people would talk about peripheral edema and maybe the edema we didn't see in the body as just kind of collateral damage.
Speaker: That's the way we did it.
Speaker: We gave it tons of fluid and then we eventually would deal with that.
Speaker: Today, maybe we don't think like that way.
Speaker: So what are some of the negative effects of fluid boluses in excess?
Speaker: Yeah, when I was first starting to train, I came into the Rivers era, you know, when you were giving tons and tons of volume, and the mantra was, you're not well until you swell.
Speaker: And that basically means that if your patient's not puffy, then you're not doing enough resuscitation.
Speaker: And certainly, that was sort of a sledgehammer to fix a major problem.
Speaker: But over time, what we realized is that
Speaker: The amount of volume doesn't only make it cosmetically bad for your patients, but there's lots of things that happen on a smaller scale or even a microscopic level.
Speaker: One of the things that happens, for example, is that you start to get edema in some of the tissues that are within encapsulated organs.
Speaker: So if you take the kidneys, for example, there's a tight fascia that surrounds the kidneys and giving lots of volumes causes interstitial edema, cellular swelling, and that has been associated
Speaker: with an acute kidney injury that comes from volume overload.
Speaker: Go to another organ like liver or the brain.
Speaker: Encephalopathy, for example, has been linked with volume overload for patients.
Speaker: There's a very nice study by Andre Deneau that looked at patients who are post-cardiac surgery looking for volume overload, which isn't something we'll get into during this podcast, but there is a way that you can actually see whether or not someone has too much volume on board.
Speaker: Essentially, associating
Speaker: volume overload with patients having prolonged ICU delirium, if you will.
Speaker: And what the thought is, is that there's cellular swelling, there's interestless edema, there becomes ischemia to the normal cells, and this causes injury that manifests as ICU delirium.
Speaker: So it's not just simply the fact of, you know, you have a little bit of edema, that's going to come off, they'll pee it off later, but it's also the cellular dysfunction that happens with it and associated organ dysfunction.
Speaker: When we treat patients with shock or circulatory failure, obviously there's two extremes.
Speaker: There's patients who clinically and by history and where they are in their presentation very clearly need fluids.
Speaker: And there's patients who very clearly are volume overloaded and don't need fluids.
Speaker: But the reality is that the vast majority of patients we see on a daily basis are somewhere in between or that gray zone.
Speaker: And ultimately that's really what we're trying to be better at answering today.
Speaker: So as we move forward, what I wanted to ask you, Hany, is if you could define for us fluid responsiveness.
Speaker: Yeah, it's a tricky term, but the classic definition, if you Googled it or if you went to up-to-date, fluid responsiveness is essentially giving volume or increasing the preload by a certain amount and seeing an increase in stroke volume by 10% to 15%.
Speaker: That's the classic definition.
Speaker: of what fluid responsiveness is at the bedside.
Speaker: What other people take it to mean is that there's going to be an improvement in resuscitation.
Speaker: That means an improvement in your blood pressure, a reduction in tachycardia, a lactate clearance.
Speaker: All of those are secondary outcomes from the increase in the cardiac output or the stroke volume.
Speaker: But if you want to go to the sort of granular grassroots definition, it's a 10 to 15% increase in your stroke volume in response to a fluid challenge or increase in your preload.
Speaker: And I think that like many other therapies or interventions in medicine, we should probably think about it in terms of probabilities, right?
Speaker: So if you are fluid responsive by that definition, in many clinical contexts, it's more likely than not that perhaps fluid is helpful if that's what you think the patient needs.
Speaker: On the other hand, if you're not fluid responsive, probably keep giving somebody more and more fluid is not the right answer.
Speaker: Exactly.
Speaker: I mean, at the heart of everything, you know, we don't like if you take fever, for example, you wouldn't take somebody who has a fever, give them a therapeutic dose of Tylenol and then just keep hitting them with more Tylenol because their fever wasn't breaking.
Speaker: And we have to start shifting our mindset to thinking about fluid as a drug and prescribing the appropriate amount for a desired result.
Speaker: And if we're not getting the desired result,
Speaker: then we need to shift our thesis as to whether or not there's another reason for why this person's cardiac output is low.
Speaker: Let's move into how we predict fluid responsiveness.
Speaker: And I wanted you to start, Haney, by maybe giving our listeners a little bit of an overview of this classical framework of static measures versus dynamic measures.
Speaker: What do we mean by that?
Speaker: Yeah, so this is one of those things that I call the art and the science of volume responsiveness.
Speaker: Static measures are essentially you're looking at the patient and at that moment in time, figuring out whether or not the person is volume responsive or not.
Speaker: A good example of that would be dry mucous membranes.
Speaker: I mean, you look at the person, you're saying their mucous membranes are dry.
Speaker: So they're, you know, they're fluid down.
Speaker: So they need more volume.
Speaker: Another example might be looking at the JVP or looking at the CVP, for example, if you have a central line in the subclavian or internal jugular.
Speaker: Those are measures that you're looking at one thing and from that one piece of data, trying to predict whether or not the person's volume responsive or not.
Speaker: Contrast that with a dynamic measure.
Speaker: I think of dynamic measures as you have a hypothesis.
Speaker: you are asking the question as to whether or not the person is volume down.
Speaker: And so you're going to do an intervention.
Speaker: Typically, that would be a fluid bolus.
Speaker: You give the person a fluid bolus, and then you're gonna use some method of assessment, typically looking at the stroke volume to see if the stroke volume or cardiac output has improved.
Speaker: If it improves, then your thesis is this person is volume down.
Speaker: You've dynamically assessed the situation.
Speaker: You've done a little test at the bedside to determine whether or not.
Speaker: Now, the reason why I say it's the art and the science
Speaker: is because as we get into this, you need both of these together.
Speaker: Static measures are nice because they're quick, but they're very inaccurate.
Speaker: Dynamic measures are more accurate, but take more time.
Speaker: And we need something at the bedside that combines both of these.
Speaker: So the art of medicine is determining which patients pass the static measures, and then those people that look that they're statically down by your assessment move on to dynamic measures.
Speaker: So I try to use both of these together in conjunction as sort of the art and the science of volume responsiveness.
Speaker: And historically, you had mentioned the Rivers era, or that's around 2001, but historically, obviously, a lot of ICU clinicians would rely heavily on static measures of pressures, like the central venous pressure, the pulmonary artery occlusion pressure, and would make big assumptions regarding fluid status and fluid responsiveness based on these,
Speaker: And over time, study after study has shown that these pressures have their value, like you said, but are not great predictors of whether the stroke volume will increase when I give a volume infusion because they're useful at extremes, like we said, but most patients that we're measuring are somewhere in the gray zone.
Speaker: Could you tell us how you incorporate those static measures into your day-to-day?
Speaker: And then we can maybe dive in a little bit deeper into the dynamic measures.
Speaker: Yeah, so as you said, the static measures, study after study have shown that they're not very accurate because the reality is that the static measures work on the extremes.
Speaker: So someone who's extremely volume down, the static measure, if we're going to use CVP as our, I'm going to use CVP as our prototypical example of a static measurement.
Speaker: If our CVP is extremely low, then we can make the assumption that this person is likely volume down in the right clinical context.
Speaker: They're hypotensive.
Speaker: know they've had um you know insensible losses vomiting all that things cvp low and that you can make the assumption that that person is probably volume down and on the other extreme a person who's in extremely high cvp and has been resuscitated previous to you taking care of them they likely are volume okay or probably volume overload but most of the patients that we're having this discussion are are right in between so for me
Speaker: Static measures just help me to get in the door to figure out where they are.
Speaker: And if they lie in the middle, which is most of our patients, the next step is to engage a dynamic maneuver.
Speaker: Excellent.
Speaker: Let's talk a little bit more about the dynamic measures, which, as you mentioned, involve a hypothesis and intervention and a reassessment to confirm or exclude that hypothesis, right?
Speaker: There seems to be two big categories.
Speaker: Those dynamic measures that depend on lung-heart interactions and those that are more of a functional challenge.
Speaker: Could you just give us a general overview, Haney, of those two groups?
Speaker: And then we'll start talking about them individually.
Speaker: Sure.
Speaker: The thing to remember is that when you do a dynamic measurement, you need some objective way of measuring.
Speaker: That could be an arterial line that's obviously invasive.
Speaker: and you need an ultrasound machine to tell you what the cardiac output is doing or the stroke volume change is happening.
Speaker: And then there are a variety of other monitors that are available on the market, all with their pros and cons, whether or not you're looking at something that is sort of like a thermal dilution technique or something that's more non-invasive.
Speaker: And we can get into that, but essentially the heart-lung interactions are on the premise that in a closed system with a closed chest,
Speaker: When you apply a positive pressure, you know, I should actually take a step back and say that the dynamic measures, we have to determine whether or not they're going to be an intubated or a non-intubated patient.
Speaker: Some of the measures we can use on only intubated patients and some of them you can use on intubated or non-intubated.
Speaker: So maybe we'll get a little more granular as we move on.
Speaker: But if you have a patient who's intubated and getting mechanical ventilation breaths,
Speaker: What's going to happen is as the breath is delivered, there's going to be an increase in intrathoracic pressure.
Speaker: And that's going to decrease venous return back to the right heart over to the left side of the heart.
Speaker: And what happens is when that breath is released, it's going to allow fluid to go to the other side.
Speaker: And if the person's on the steep part of the Starling curve, we expect to see some sort of change happening, an exaggerated change happening.
Speaker: And this would indicate to us that the person is in fact falling responsive.
Speaker: The prototypical classic one that we talk about is something like stroke volume variation or pulse pressure variation.
Speaker: If you see a large amount of stroke volume variation or pulse pressure variation during a few mechanical breaths, it tells you that that person is likely volume responsive, and then you should proceed with a volume challenge at that point.
Speaker: I'll pause there to see if there's any questions.
Speaker: Well, I think one of the important distinctions that you made
Speaker: Haney was regarding non-ventilated and ventilated patients, right?
Speaker: And especially when we are leveraging or utilizing the heart-lung interactions, right?
Speaker: It's more commonly that we're using these in intubated patients because it's more pronounced.
Speaker: Could you talk about some of the conditions that are necessary for those measurements of pulse pressure and stroke and systolic volume variation to be really ideal?
Speaker: Yeah, so that's a great point.
Speaker: So when you have somebody who's mechanically ventilated and you're looking for stroke volume variation or pulse pressure variation, there's not that many things that you have to worry about.
Speaker: You only have to worry about whether or not the person's in sinus rhythm and that they're mechanically ventilated at 8 to 10 cc's per kg, that they're not spontaneously breathing, there's no RV dysfunction, they have normal to moderate PEEP, their chest is closed, they have no forms of mechanical assist devices, and there's no abdominal hypertension.
Speaker: That's like
Speaker: Pretty much every patient that we see, right?
Speaker: All those things are checked off all the time.
Speaker: Obviously, I'm being sarcastic here.
Speaker: This is one of those things where to do a true dynamic test with someone who's mechanically ventilated, it's very, very hard to find somebody who checks all those boxes.
Speaker: And this is one of the reasons why doing these tests at the bedside should be used with limitation.
Speaker: I know plenty of people that do these tests and look for a lot of swing in the arterial line, and they just kind of guesstimate and gestalt it.
Speaker: It's been shown that that's kind of okay, but if you want to do the test and really restrict fluid for patients who don't need it, you have to make sure that all of these checks are checked off.
Speaker: And again, regular heart rate, that means sinus rhythm.
Speaker: You know, mechanical ventilation, eight to 10 cc per kg.
Speaker: They can't be spontaneously breathing.
Speaker: No RV dysfunction, normal to moderate PEEP.
Speaker: And the studies don't even say what moderate PEEP is.
Speaker: They just say normal to moderate PEEP and closed chest environments.
Speaker: And it's interesting that there's been more and more studies recently that show that perhaps the 8 mL per kilogram, we can do with a little bit less than that.
Speaker: There's some other conditions that may or may not be present, but ultimately what it really tells you is ideal conditions will optimize the predictive value that's what's been published in studies, right?
Speaker: And the problem is that when people translate this to the bedside, as they become less rigorous with these conditions, the predictive value starts declining.
Speaker: And in some patients that you're truly in the gray zone, that could be a problem, right?
Speaker: It could give you the wrong answer.
Speaker: However, if you do everything by the book in these patients, obviously the predictive value increases, and that might give you a better answer.
Speaker: But it's also important to remember that when we have patients who don't meet these conditions, there might be other tests that we can do, and we'll talk about those in a second.
Speaker: Any other comments on this particular topic of the dynamic measures that require the lung-heart interaction of ventilated patients?
Speaker: No, just two or three points that I want to make.
Speaker: The first thing is that if you're doing it by the bedside, don't forget that, you know, when we say, you know, eight to 10 cc's per kg and you're ventilating them at a lower tidal volume because of ARDS or whatnot, realize that this tidal volume is only during the period where you're asking the question for the test.
Speaker: So you might give them a dose of analgesic just to sort of,
Speaker: allow them to tolerate the breath so that they're not spontaneously breathing.
Speaker: That's okay.
Speaker: I mean, that's okay to do it for that period of time, but it's not that they had to have been ventilated for that amount of time.
Speaker: And then the second thing is that if you're going to do pulse pressure variation or stroke volume variation, one of the things I like to do on the monitor is actually decrease the sweep speed of the monitor because what we're going to be doing, and maybe we won't get in the weeds about how to calculate pulse pressure variation, but sometimes
Speaker: the A-line tracing going at 25 millimeters per second is a little bit too fast.
Speaker: And so what you'll do is you'll actually slow down the sweep, go to like 12 and a half, and that's going to put a lot more tracing up on the screen so that you can see it and you can calculate and you can find the largest pulse pressure and the lowest pulse pressure and do your calculations from there.
Speaker: I think it's worth, I mean, reminding our listeners because obviously the way of calculating either pulse pressure or systolic
Speaker: stroke variation is the same.
Speaker: So like you said, it's basically your maximal minus your minimal divided by your mean.
Speaker: And that gives you a number that's expressed as a percent.
Speaker: Could you tell us how you would interpret that percent?
Speaker: Yeah, and you know, it's funny because I love this stuff, so I read as much literature as I can, and the numbers, they're all over the place about where the cutoff is, but let's just remember that somewhere between 12 and 15 percent of a pulse pressure is the cutoff for volume responsive and not.
Speaker: And what that means is that if your pulse pressure variation is less than, well, again,
Speaker: 12 to 15%, that means that the person is not volume responsive.
Speaker: And if your pulse pressure is greater than that threshold, then they are likely volume responsive.
Speaker: And I think a way of equating that or inserting that into the Starling curve that we talked about is if you are below 12 and the lower you are, the more likely you're on the flat portion of that curve.
Speaker: And if you are above 15 and the higher you are, the more likely you're on the steep portion of that curve.
Speaker: Would that be a correct assessment?
Speaker: Perfectly stated.
Speaker: And another thing I just remember is like, how are you going to remember all these numbers?
Speaker: Just remember what a positive stroke volume response is.
Speaker: It's an improvement in 10 to 15% of your stroke volume.
Speaker: So all these numbers tend to hover around that, you know, 10 to 15% point.
Speaker: And that applies for all multiple choice questions with percents.
Speaker: You'll say 10 to 15, right?
Speaker: Exactly.
Speaker: Exactly.
Speaker: So this is also a how to do better on standardized exam type podcast as well.
Speaker: Well done.
Speaker: There you go.
Speaker: So.
Speaker: We talked about these dynamic measures that we can utilize on patients who are ventilated.
Speaker: And these, to be honest, are also kind of the early dynamic measures that people have studied and published.
Speaker: But as we move forward, there's other things that came along.
Speaker: And I wanted to ask you, before we go to the true functional test, if you could talk about the inferior vena cava and variations in that diameter and how that applies.
Speaker: And that's obviously something that is done with ultrasound.
Speaker: Yeah, I love ultrasound.
Speaker: And one of the things that was pushed relatively early on during ultrasound's ascent to what it is today is using IVC as a determinant as whether or not someone is volume responsive or not.
Speaker: And you can and you can't use ultrasound.
Speaker: Let me explain.
Speaker: If someone is spontaneously breathing, you cannot use ultrasound as a dynamic marker of volume responsiveness.
Speaker: You need to be on positive pressure, all the things that we talked about before.
Speaker: If they're spontaneously breathing, it's a static measure.
Speaker: And again, what a static measure means, it just tells you what the extremes are.
Speaker: So I have a patient who is a trauma patient.
Speaker: They're exsanguinating.
Speaker: I look at their IVC and I see a thin, paper thin, like the IVC is hardly filled with any fluid.
Speaker: That would suggest to me that a person who's hypotensive and I see that is likely to be volume down.
Speaker: On the other hand,
Speaker: If I see an IVC that's big, plump, there's no variation.
Speaker: Again, in a non-intubated patient, this would suggest to me that the person is volume overloaded or there's some sort of RV dysfunction or pulmonary hypertension, something downstream that's causing that IVC to become plump.
Speaker: Most of our patients though kind of fall in between.
Speaker: So IVC in a spontaneously breathing person is only a static measure.
Speaker: That's not gonna do.
Speaker: However, if you have a patient who's mechanically ventilated
Speaker: And again, all those things we talked about, they're in sinus rhythm.
Speaker: They're getting controlled ventilation.
Speaker: There's no spontaneous breathing, no RV dysfunction.
Speaker: You can use the changes of your IVC during a breath-to-breath situation to determine volume responsiveness.
Speaker: That's called the distensibility index or the DI index.
Speaker: Essentially, what you do is you take your maximum diameter, subtract it from the minimum diameter, and divide it by the minimum diameter.
Speaker: And that's all within one respiratory cycle.
Speaker: So as the mechanical breath is delivered, we increase intrathoracic pressure.
Speaker: That should make the IVC pop right open.
Speaker: That's going to be the maximum diameter.
Speaker: And when that breath is released, the IVC should come down to its minimum diameter.
Speaker: Take one respiratory cycle, take the maximum, minimum, divide it by the minimum.
Speaker: Here the number is 18%.
Speaker: If your variation is less than 18%, it suggests that the person is not volume responsive.
Speaker: Greater than 18%, it suggests that they are volume responsive.
Speaker: So you're taking IVC,
Speaker: And depending on whether they're mechanically ventilated or spontaneously breathing, we're looking at dynamic or static measurements respectively.
Speaker: And this is a very important point that I want to emphasize because like you mentioned, Haney, as we became more and more proficient and ultrasound is utilized more and more at the bedside, at one point, a lot of people translated some of these
Speaker: in a way that probably did not justify based on what we know in terms that they were using dynamic, as a dynamic measure, the IVC in people who were not intubated.
Speaker: And it doesn't give you all the answers.
Speaker: And like you said, you can definitely measure that same lung-heart interaction that we're measuring with the A-line.
Speaker: You can measure in the right conditions in patients who are intubated.
Speaker: And otherwise, basically, you're using it as a surrogate for a static measure
Speaker: that you can also use many others that you mentioned earlier.
Speaker: And I think that that distinction is important because a lot of people would just put the probe and make an overall assessment, right, of what we should do.
Speaker: And it's not always that easy.
Speaker: Yeah.
Speaker: Every time I go teach in an ultrasound course, you know, they usually have these healthy, you know, 20 to 30-year-old people who are the models.
Speaker: And whenever it's time to look at the IVC, you know, they look at the IVC, they're like, it's really small.
Speaker: And then they look over at the models like, are you dehydrated?
Speaker: Are you feeling thirsty?
Speaker: And the person's like, no, I feel fine.
Speaker: And that's just a testament to the fact that the IVC in the spontaneously breathing person really reflects nothing else more than the central venous pressure.
Speaker: And in the young, healthy person with no RV dysfunction, we should expect a CVP to be less, you know, to be zero to five.
Speaker: So, you know, I just want to kind of point that out.
Speaker: When you look at healthy people in your scanning, you see their IVC as normal.
Speaker: It does not mean that they're volume down.
Speaker: Excellent.
Speaker: So let's move forward and talk about the truly functional dynamic challenges or methods.
Speaker: And maybe we can start with a passive leg raising.
Speaker: Yeah, whenever you use these measurements, really any measurement that's dynamic, the first thing we probably should talk about is how you're going to do the assessment.
Speaker: And one thing we should be very cognizant of is that blood pressure does not indicate a positive or negative response.
Speaker: Tachycardia,
Speaker: also doesn't indicate a positive or negative response.
Speaker: And certainly sending lactates on all these tests takes too long to figure out.
Speaker: So you essentially need a way to assess the stroke volume when you're doing these tests.
Speaker: So that should be the first stop is how are you assessing stroke volume or cardiac output?
Speaker: I like to use ultrasound.
Speaker: I admit that for people who are doing repeated assessments at the bedside, it can get a little complicated because every time you have to bring the machine over,
Speaker: assess the stroke volume, you're going to have to look for VTI and all sorts of indices that people might not be familiar with.
Speaker: There are other things that are out there.
Speaker: There are things, the non-invasive cardiac monitor, the Nikon by Cheetah, and I don't get paid by anybody, but these are the things that are out there.
Speaker: It's a non-invasive way that's been shown to correlate somewhat to what the stroke volume actually is.
Speaker: If you have a patient who has a swan-Gans catheter, then you could do that then.
Speaker: The issue there is that you're going to see what the stroke volume is before
Speaker: and after you do the test.
Speaker: So whatever monitor you use, it is very, very important that you have something that's going to tell you what the stroke volume is when you start to do this dynamic indices.
Speaker: Excellent.
Speaker: So should we, yeah, I was just going to say, should we go into then the passive leg raise and what that is?
Speaker: Yep.
Speaker: Let's talk about that.
Speaker: Perfect.
Speaker: Okay.
Speaker: So the passive leg raise, it's really my favorite test of all to do because for a few reasons, the first is, is actually,
Speaker: been shown to be the most accurate test to determine fluid responsiveness as a dynamic test.
Speaker: And I'll explain how to do it, but I just want to kind of go over why it's such a good test.
Speaker: The second reason is you can be spontaneously breathing.
Speaker: In other words, you don't have to be mechanically ventilated, or you could be mechanically ventilated.
Speaker: You can be in sinus rhythm.
Speaker: You can be in AFib.
Speaker: You can be all the other things that we talked about before with all the limitations for doing dynamic testing for the ventilated person.
Speaker: You can have all of those with the passive leg raise.
Speaker: And the passive leg raise, most of all, the reason why I like it most of all is because it gets everyone on the team involved.
Speaker: And I'll explain why.
Speaker: So essentially what you're gonna do is you're gonna start off with your patient's head of the bed elevated 45 degrees, and you're gonna have to get your baseline stroke volume before you do the leg raise.
Speaker: You get your baseline stroke volume, and then what you're gonna do is you're gonna elevate the legs 30 to 45 degrees and wait between 60 and 120 seconds.
Speaker: What this does is it allows 200 to 400 cc's, depending on the lurcher you read, of blood that is in the lower extremities and the mesentery,
Speaker: to flow back into the central circulation.
Speaker: You're basically giving your patient an autologous fluid bolus of their own fluid.
Speaker: And then you're going to check the second stroke volume and see if there's a delta.
Speaker: Again, what are we looking for?
Speaker: 10 to 15% increase in their stroke volume.
Speaker: If that happens with a passive leg raise, then you have identified a person who will benefit from exogenous fluids to be given.
Speaker: The best part about this test is that they're not responsive if their stroke volume was, let's say, 6%.
Speaker: then you can put the legs back, put the head of the bed up, and the blood will settle back into those capacitance veins.
Speaker: And you haven't given that person any extraneous volume.
Speaker: So it's extremely predictive, and it's also safer for your patients where you're not just giving them crystalloids to, you know, see what happens with your patients.
Speaker: And I think that I'm also a big fan of the passive leg raise, and I also find that the additional reason why it's so cool is because it's so simple in terms of its concept, right?
Speaker: And it's not fancy.
Speaker: It's something you can do right there.
Speaker: And you basically are doing the control experiment without the potential of harm, which we'll talk about in one of the other fluid challenges, which is with fluid actual.
Speaker: Any other caveats or tips you can give us for the passive leg raising, Haney?
Speaker: No, the only thing I would say is again, don't rely on tachycardia or hypertension to be rule in or rule out things.
Speaker: There are many times where patients find this uncomfortable and they make it a little more tachycardic or their blood pressure might increase just because of the sympathetic increase and the fact that you're doing something to them.
Speaker: So don't rely on that alone.
Speaker: But if you're looking for a test that gets everyone on the team involved, gets medical students involved because they're the ones holding up the legs, there's no better test than the passive leg raise.
Speaker: And again, as I said before,
Speaker: If you look at the studies across the entire landscape of this literature, the passive leg raise has held up to be one of the most predictive tests.
Speaker: Excellent.
Speaker: The second test that I wanted to talk in this particular group, which is a newer test, but kind of combines a little bit of the lung interactions, but also some of the benefits of the passive leg raising is the end expiratory occlusion test.
Speaker: So that's a really cool test because obviously they're going to be mechanically ventilated here.
Speaker: And in this test, what you're going to do is you're actually going to hold the person at the end of expiration.
Speaker: So the person will have their inspiratory cycle, the Huff expiratory, and then you're going to do an expiratory pause and you're basically ceasing airflow into the chest.
Speaker: So you're minimizing the amount of positive pressure that's there, except for the peep that's on the ventilator.
Speaker: And that's going to allow the right heart to fill.
Speaker: And then with the next breath, you're going to release, and then you're going to see an exaggerated response.
Speaker: So there are some studies that say you can actually do this for somebody who's in atrial fibrillation, which is another nice thing, too, if you're not willing to do the passive leg raise.
Speaker: And a change in 5% tells you that the person is likely volume responsive.
Speaker: So it's a nice, easy test.
Speaker: They don't have to be paralyzed.
Speaker: It just checks a lot more of the boxes than using pulse pressure variation in someone who's mechanically ventilated.
Speaker: Excellent.
Speaker: And finally, the other functional tests that a lot of people have utilized for a long time are actual fluid challenges.
Speaker: And now the discussion is where you do a regular fluid challenge or a mini fluid challenge or conventional fluid challenge.
Speaker: Could you tell us what the fluid challenge consists of and what are the pros and cons?
Speaker: It really depends on what literature you read.
Speaker: I think it's kind of all the way out there.
Speaker: The classic that I've read is anywhere between 300 to 500 cc's rapidly infused constitutes a volume challenge.
Speaker: And so you infuse that amount of volume and you get a 10 to 15% change.
Speaker: That's like the classic definition.
Speaker: But there's plenty of research showing that using as little as 100 cc's of crystalloid would be predictive for you.
Speaker: Now, the thing that's
Speaker: really important when you're doing a volume challenge is that sometimes the nurses, you say, I need a bolus, they'll put it on 999 on the pump.
Speaker: And to really do an effective fluid challenge, you have to have it on a pressure bag.
Speaker: In the OR, they'll even fill up a syringe and just push it through.
Speaker: Because essentially what happens is with the 999 method is the fluid goes in, but it doesn't go in particularly very fast.
Speaker: And so fluid has time to extravasate, fill the interstitial spaces, and you don't have a lot of intravascular volume.
Speaker: My goal when I'm doing a fluid challenge, whether it's doing a passive leg raise or a mini challenge, is to give them some amount of volume to the central circulation and then ask the second question, was there a delta in my stroke volume?
Speaker: So that's the difference for me.
Speaker: And obviously it's an important distinction in terms of when we're really trying to predict fluid responsiveness by measuring the impact on stroke volume versus what people say, let's just do a fluid challenge or let's just give a fluid bolus, which like you said is the order
Speaker: 250, 500, whatever it be, any type of fluid, and then just give it at 999.
Speaker: That's just giving fluid blindly.
Speaker: In some situations, it might be appropriate clinically, but as we get to that gray zone and we really want to know, you probably have to be assessing the stroke volume effect or the delta in the stroke volume as you do these.
Speaker: Exactly right.
Speaker: And the obvious, I guess, negative to the fluid challenge is that
Speaker: once you gave the fluid, it's in the patient.
Speaker: And if you are on the wrong side of that curve, you may have caused a little bit of harm.
Speaker: Exactly.
Speaker: Yeah, you're raising their fluid balance.
Speaker: Then you're like, oh, now I have to diurese them later on today.
Speaker: So it's filled with a whole bunch of things.
Speaker: There is one more test that I found very useful.
Speaker: There's not a tremendous amount of literature for it, but it also works well as a dynamic test.
Speaker: And that's the end tidal CO2 test.
Speaker: That's essentially using end tidal monitoring
Speaker: to assess your patients.
Speaker: Is that something you want to go over?
Speaker: Yeah, absolutely.
Speaker: So the really cool thing about this is that this is a way that you can assess cardiac output.
Speaker: So you don't have to worry about ultrasound.
Speaker: You don't have to worry about non-invasive cardiac monitor.
Speaker: The end tidal CO2, as long as the person is not having any change to the ventilator or any change to their respiratory status, you can use cardiac output to be a surrogate for your stroke volume or your cardiac output.
Speaker: So end tidal CO2, you'll get a baseline number, and then you'll do a passive leg raise, or you'll do a mini fluid challenge, whatever you decide to do.
Speaker: And then if you see a change in your end tidal by 5%, that would suggest to you that the person is in fact volume responsive because you're seeing an increase in their cardiac output.
Speaker: If you see no change, then you can safely assume that, you know, don't bother with the fluid.
Speaker: That person's not volume responsive.
Speaker: Now, the studies out there, they're not a tremendous amount, not as much as the stuff we've been talking about.
Speaker: But I think if you're in a place where you don't
Speaker: have access to ultrasound, you're not very facile with ultrasound, or you don't have access to any of these other things, that might be a good alternative to you to doing a dynamic measure.
Speaker: It's important also to recognize, Hany, that there is an element that depends on the patient in terms of selecting the test, right?
Speaker: Like, for example, if you're ventilated and you're not having spontaneous breaths and you have an A-line, well, you got your stroke volume variation that you can look at there.
Speaker: There's also an element of expertise
Speaker: If you are facile like you are with ultrasound, that might be the easy way to do it.
Speaker: But this end tidal CO2 is newer, like you mentioned.
Speaker: It hasn't been studied as extensively.
Speaker: And perhaps the predictive value is not at the same level as some of the others, but definitely seems to be an alternative that can also help guide, especially in being a little bit more deliberate of how we will associate these patients in that gray zone.
Speaker: Perfectly stated.
Speaker: So as we wrap up, Hany, could you give us like a overview of how you put it all together at the bedside in your clinical practice?
Speaker: Just walk us through in terms of how you would think about this if you were working at the bedside today and were trying to answer this question.
Speaker: Yeah, so as I receive a patient and my question becomes, is this patient volume down?
Speaker: The first thing I need to do is figure out, you know, am I going to go through the trouble of doing a dynamic measure?
Speaker: And so, again, for that, I'm using static measurements.
Speaker: I'm personally using ultrasound.
Speaker: It's at the bedside for me.
Speaker: I'm using it for other diagnostic purposes, so it's really not that big of a deal for me.
Speaker: I'm using the IVC to see whether or not that person is razor thin or if it's dilated.
Speaker: Again, we're talking about someone maybe who's not mechanically ventilated.
Speaker: The other thing we didn't talk about, but you can just look at chamber size of the heart, whether or not the RV and the LV are empty.
Speaker: Those are all things, again, that are very static.
Speaker: If the person checks that box and they look like they are, you know, volume down, the IVC is paper thin, I then go on to do my secondary tests.
Speaker: I do a passive leg raise.
Speaker: I'll do a fluid bolus, all the while knowing that I'm using ultrasound to determine what the change in stroke volume is for that patient.
Speaker: And
Speaker: You know, when I'm upstairs, because in the ED, it's kind of easy because many patients who come in, they're already volume down.
Speaker: It's when they're upstairs in the ICU, they're two to three days in, that's when it becomes more of a challenge.
Speaker: And that's when I have to have a lot more discretion for that patient.
Speaker: Maybe then I'm not doing static measures.
Speaker: Maybe then I'm jumping to dynamic measures because I assume that person has already been volume resuscitated.
Speaker: I'll take a look at the heart again.
Speaker: I'll do my dynamic assessment with passive leg rates or I'll use end tidal CO2 change.
Speaker: And then I'll see what happens when we do a passive leg raise or we do a mini fluid challenge.
Speaker: Sometimes, frankly, the person is having surgical issues where I can't do a passive leg raise.
Speaker: Sometimes we have amputees who don't have any legs to passively raise.
Speaker: So in those cases, I might go with a fluid challenge, the mini fluid challenge for that person.
Speaker: But whatever it is, whenever I'm asking that question, I have to assess if there's a delta in my stroke volume.
Speaker: And that's exactly what I do at the bedside.
Speaker: Excellent.
Speaker: And there are obviously very few existential questions that are pervasive and present throughout time.
Speaker: What's the purpose of life?
Speaker: Is there life outside of the earth?
Speaker: And should I give my patient more fluids?
Speaker: At least we've elucidated it and gave some clarity or more clarity on one of them, Hany.
Speaker: So I really appreciate that.
Speaker: No, listen, if I could figure out what to do, I would easily retire from medicine because this is one of those questions that has been
Speaker: pervasive through, I mean, any textbook that you've read in the past, you know, 67 years asked the question of how do you determine if the person's volume responsive?
Speaker: And again, like I said before, it's amazing that we can do robotic surgery across an ocean.
Speaker: We still can't figure out how to give our patients the right amount of fluid.
Speaker: But like many things in medicine, it's about having better questions than having all the answers.
Speaker: So I think it's a question worth trying to answer because it forces us to think,
Speaker: little bit more deliberately about the potential harms and to treat fluids like you said, Haney, as a drug that has a therapeutic window and that can both help but also can cause harm to our patients.
Speaker: Absolutely.
Speaker: So you've been on the podcast before, Haney, and we'd like to close with a couple of questions that are unrelated to the clinical topic.
Speaker: We have talked in the last one you were on about books and other things.
Speaker: So today I want to ask you a couple of different questions, and I really want to
Speaker: make sure that we take advantage of your expertise as an educator who's really trying to utilize new platforms, move the ball forward in terms of reaching an enormous amount of learners.
Speaker: And really one of the pioneers in our field on what started as a hashtag foam.
Speaker: If you could just tell us what that is and then we can talk about some specifics.
Speaker: Sure, free open access medicine or foam was a concept not
Speaker: created by me, but by Chris Nixon and Mike Cadogan from Australia, their concept was if we say learn on social media, people are going to just click off and not even be receptive to it because social media has so many negative or immature connotations.
Speaker: So they came up with this nifty concept, ironically, while at a bar looking at the foam on the top of their beers.
Speaker: So this free open access medical education concept or this hashtag has come up, you know,
Speaker: when I was first getting going in medicine, you know, like 10 to 12 years ago in residency.
Speaker: And essentially what that is, is people putting education out there on social media platforms.
Speaker: The prototypical is Twitter, but now Instagram is a growing platform, even on TikTok, people are doing it.
Speaker: But social media is really any way to disseminate medical education.
Speaker: There are great YouTube channels and LinkedIn and, you know, it's kind of infinite, but any way you disseminate information over social media network would be categorized as FOMED.
Speaker: Excellent.
Speaker: And why don't you give us some of your favorite or some good channels to explore?
Speaker: You're obviously very, very active on a lot of these, but if you could just give us maybe a couple of people to follow on Twitter, on Instagram, TikTok, or YouTube.
Speaker: Yeah.
Speaker: And this is going to sound like a shameless plug, but I hope it doesn't.
Speaker: If you go to criticalcarenow.com, which is my website with a collective of 40 educators,
Speaker: All of those people are active on social media.
Speaker: So you'll be able to find really good educators who are publishing there on social media.
Speaker: And some examples that come to mind are Steve Haywood.
Speaker: He's really big into airway and ventilation.
Speaker: Matt Shuba, he's at ZenTensivist.
Speaker: Steve Haywood, by the way, is at HeySteveMD.
Speaker: ZenTensivist is Matt Shuba, who is so well-versed in ventilation, likes to go over abnormal vent waveforms and troubleshoot those.
Speaker: Anand Swam and Nathan is an emergency medicine doc who really does all facets of emergency medicine and resuscitation.
Speaker: And yeah, that's who I can think of right now.
Speaker: And both of those people, all those people are also on Instagram as well.
Speaker: TikTok is a platform that I'm on and I'm sure that's going to give a few people a chuckle, but that is really a growing community of educators who are very good at doing video education and
Speaker: The people that I follow, the people I watch on TikTok, no one's dancing, no one's shaking it to music while medical facts on the screen.
Speaker: They're all just looking at the screen and doing very fun, medically focused education.
Speaker: And I have to say that the reason why we're having this podcast is because of Heini.
Speaker: He inspired and pushed me forward to start a podcast as a way of sharing content with clinicians at the bedside.
Speaker: And I still have the first microphone that you sent me, Haney.
Speaker: Thank you very much to get me started.
Speaker: But I wanted to ask you about podcasts outside of medicine that you'd like to listen to or you'd like to recommend.
Speaker: Yeah, you know, it's kind of all over the place.
Speaker: And I don't want anyone to take this the wrong way.
Speaker: But one of my favorite podcasts to listen to when it's not controversial is actually the Joe Rogan podcast.
Speaker: I like to listen to people who are good interviewers, who ask really good questions.
Speaker: And until the whole COVID thing, we won't get into it.
Speaker: It's a podcast I just truly enjoyed.
Speaker: Another more classic podcast that I like to listen to is 99% Invisible.
Speaker: That's also a really well done one, just kind of in the classic sense of podcasts.
Speaker: But
Speaker: You know, these days, I'm spending less time on podcasts and watching more of these video casts on social media.
Speaker: But those are the ones I tend to enjoy.
Speaker: Excellent.
Speaker: Are there any other teaching platforms that you think are worth exploring?
Speaker: So we did talk about critical care now, and we'll have the links.
Speaker: And obviously, you're the founder.
Speaker: But more importantly, I think it really congregates an enormous amount of people who are very active with different areas or niche of expertise that I think have a lot to offer to our learners.
Speaker: If you're into emergency medicine and that practice, I think you can't go wrong with EMRAP, which is Mel Herbert, who's over the years created a juggernaut of an amazing channel of podcasts, videos, procedures.
Speaker: It's an outstanding resource for anybody who's really into emergency medicine.
Speaker: And then for critical care type stuff, again, criticalcarenow.com,
Speaker: And Rebel EM, which comes across as an EM website, but it actually has a lot of critical care and resuscitation stuff as well.
Speaker: You know, we run a conference every year called ResusX.
Speaker: This is a shameless plug, but if anyone is interested in that, we record the conference and we have them available on resusx.com.
Speaker: And then we do live conferences yearly.
Speaker: So anyone can go check that out and see if it's right up there.
Speaker: We have free offerings as well if people don't want to purchase the conference.
Speaker: We have a sampling of like six or seven videos that you can watch by really amazing experts in critical care.
Speaker: So check it out.
Speaker: And ultimately in 2021, the availability of great information is not the problem.
Speaker: It's being able to curate and distill it and just utilize it.
Speaker: So what I would encourage our listeners is to sample some of these through the links and then find what fits your personality and your learning experience
Speaker: habits better so a lot here that hey hey has shared and we'll put all those in the in the show notes thanks very much haney so let's shift gears a little bit and talk about music and i'm interested in hearing from one artist or maybe a specific album you want to be more more granular that you often gift or recommend to others to explore oh that's such a good one and and music is such a deep part of my life you know i maybe
Speaker: Maybe I'm overstating this, but I was a musician at one point, thought about doing music professionally.
Speaker: So I really, really love music and it's my happy place.
Speaker: All that being said, there's too many people to think of.
Speaker: I'm going to just pick one.
Speaker: The first thing that popped in my head when you said that is a band called Wilco, W-I-L-C-O.
Speaker: They're kind of an alt country band, but their genre breaking, their songwriting is so unique, so special.
Speaker: Many people might not know them or they don't have any top 10 songs that you might hear on the radio, but just a tremendous amount of songwriting and lyricism by Jeff Tweedy.
Speaker: It's just one of the bands that I listen to continually.
Speaker: And as a testament to how it stands the test of time is even my kids listen to Wilco.
Speaker: So I know it can't be that bad if my kids are listening to it.
Speaker: Well, that's perfect.
Speaker: And the whole point of these questions is to open our minds in,
Speaker: give us paths to explore.
Speaker: I have never heard of Wilco, but I definitely will check them out, Haney.
Speaker: I'll let you know what I think.
Speaker: I'm excited not to discover a new band that I have not heard of before.
Speaker: So that's awesome.
Speaker: And as we close, Haney, I just wanted to ask, is there anything that you want every listener to know?
Speaker: Could be a quote or just a thought to close the podcast today.
Speaker: Yeah, this is one that I thought a little bit about and I'm going to resort to
Speaker: back to some of the themes I'm seeing on social media.
Speaker: And I don't want to bring things down, but I will just for a second only to bring it back up.
Speaker: You know, this has been such a test for us in healthcare these past two years to experience a disease that, you know, in COVID that we've never seen before, the shortages, the stress that we've had to deal with, the violence against healthcare and the patients complaining about
Speaker: Not getting therapies and vaccines.
Speaker: We've been through hell.
Speaker: I don't even say back because I think we're still there.
Speaker: And so many people reach out to me on social media and they're angry and they're frustrated.
Speaker: But the thing I want people to take away is, you know, this for me was my calling.
Speaker: You know, I'm not the person that's going to be breaking up a bank robbery or running into a burning building to save people.
Speaker: And just that's that's what other heroes do.
Speaker: And I'm not calling myself a hero, but this has been the job that I've been asked to do is to help this pandemic.
Speaker: And I want people to keep perspective that this has been a very, very hard fight, but it will come to an end.
Speaker: But I want people to remember that at the end of the day, this is what we trained to do.
Speaker: This is our time.
Speaker: And I don't want people to get frustrated and leave the profession.
Speaker: Just think about all the amazing things that you have done at this point into your career and think about the thousands of patients that you still have ahead of you.
Speaker: So this is definitely a downer in anyone's career.
Speaker: There are people who are thinking or have left the profession, but put it into perspective.
Speaker: Think about the things that you do every day and think about how many lives you have yet to change beyond the pandemic.
Speaker: And I just want people to think and put that into perspective just so that they can be happy.
Speaker: And even though this is tough, still wake up every day and grind it out.
Speaker: But again, this is our challenge.
Speaker: This is what we were asked to do.
Speaker: And there are challenges, but we will get through this and we'll get to the other side.
Speaker: And I think down the road, people will have a greater appreciation for the fact that while people were asked to stay home, we were, you know, driving to the hospital, we were going to work and we were doing things that other people couldn't do.
Speaker: So those are my closing thoughts.
Speaker: That's just my perspective that I want to give to other people.
Speaker: Very well said.
Speaker: And I think it's a perfect place to stop.
Speaker: I could add my comments, but I think that we'll leave it with your beautiful words.
Speaker: And again, thank you, Haney, for everything you do.
Speaker: Thank you for being on with us today.
Speaker: And I look forward to having you back on the podcast soon.
Speaker: Sergio, it's always a tremendous honor to be on here.
Speaker: Thank you for having me.
Speaker: And the one thing that just popped my head before I let you go is don't forget Sergio Zanotti was also at ResaSaccess faculty.
Speaker: So another reason to go check that out.
Speaker: He did a tremendous job this year and last.
Speaker: Thanks, Haney.
Speaker: Talk to you soon.
Speaker: Be well.
Speaker: Thank you for listening to Critical Matters, a sound podcast.
Speaker: Make sure to subscribe to Critical Matters on Apple or Google Podcasts and share with your network.
Speaker: Sound's transforming the way critical care is provided in hospitals across the country.
Speaker: To learn more, visit www.soundphysicians.com.
