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that You can see that. Yes, you can, Everybody. You see this? Yes, we do. Okay, fine. So Ah, Good evening. Um, thanks for coming tonight. Um, as you just heard Still walk to go on Google. And today I want to carry on yesterday's talk. Uh, this is like a trulyclear talks that we're all stemming from the common concept of delivering oxygen to the tissues. And we said cardiac output was a very important factor of the three factors. And the commonest thing will be dealing with view of cardiac output on a day by day basis is fluids how to fill somebody how to improve your pre load. And so yesterday we talked the the consequences of of guessing wrong, but either getting too little or too much fluid. So today we're going to talk about something that I'm surprised that so few people know about or no in depth or understand, that is the physiology of venous return. And so I'm going to try and introduce some concepts that I hope our new, but often I find they are new. So here we go. Okay. So, going right back to the beginning, The paradigm I always start with. We're trying to improve oxygen delivery that's old can do. And the craziest chaotic situations. Just simplify things. If your card it happen. Hemoglobin and statue Ricans are okay. You're okay. I know this is a bit repetitive, but I think it's really important to stroke. Really? Keep that in the back here ahead. Whenever you're dealing with something that you're not familiar with your not comfortable with, you do those three simple things in your okay. So today we're gonna talk about cardiac output, and we're gonna talk about one of the aspects of it that is preloaded the words venous return. So we're going to start with the clinical case these again? These are all true stories. I promise you two stories that I went through, I lived with so 63 old woman came in and he had been overseas. Came back, uh, with three days of very bad nausea, vomiting and severe profuse diarrhea. He arrived on the Thursday afternoon at 16. 30 in the accent emergency department of our hospital. And when she came in, her BP was low. Heart rate was fast for your now it was poor and her lactate that's important was seven, which is very high. The normal be less than two. Well, listen to. So to resuscitate her, the doctors at the accident Virgin See department gave her almost 10 liters of crystalloid they fit, but he was very dry and needed a lot of fluid. And the result of that and that result was obtained in the early hours of the morning of the Friday morning to the next day was the BP was now pretty much the same. The Harvoni was slightly faster. The urine output dropped even further and are lactate. This is most important, didn't go down. It went up to a very high level. So it's 7. 30 in the morning. They called are Intensive care unit and they spoke with me and I was with my my I was with the registrar in the intensive care unit and they said, Could you please admit this picture? And I said, Absolutely, we can take the speak and I turned to the register and I said, this patient will be dead within the hour, But I was wrong. He took her 20 minutes before she had arrested and died, So the question I have for you is what were the two things that they did wrong to if you really want to guess isn't nearly 10 liters of crystalloid. Well, okay, Anything else? So in the chart box, we also have high concentrations of crystalloids. They would have transfused. Um, Jasmine is saying admitting her. Teo, I see you A She's still not stable. Okay, I think you're getting on the right track. So it would have been reasonable to give her a couple of leaders. That's a maximum of fluid crystalloid and see your port improves. But at 10, leaders were close to 10 liters. They're basically not improving her, and he's not responding to fluids, So that's the first thing. Second thing he needs to have improved cardiac output. The fluids are not doing the job, so she's not fluid responsive. So what they should have done was when they saw that they weren't getting it improved cardiovascular system with a couple of leaders, they should have called us immediately because we then would use somewhat more sophisticated monitoring techniques, and we probably would have given her another. Uh, we use another approach to improve her cardiac output. So what were we we would have done was this. So this is the normal again, the normal starling curve. That's where you and I are. And we all respond to fluid, which means if I give you fluid, you or me or anybody or someone who's sick, we think response. You give them fluid and you optimize your feeling first to get the cardiac output where you want it to be. And that's fine if it works. But if you're on the flat part of your starting curve and you keep feeling fluids, it's gonna do nothing for your cardiac output, but it will increase the pressure in your heart. That's bad, as you saw last time. So if it doesn't, if you can't get an improved cardiac output with some fluid like two leaders, let's say then you want to do something different. So when you want to do is king your StarLink er and how would you do that? But one of the ways you do it is used in the trucks, cardiac stimulants and thereby you increase the cardiac output for the same feeling. Pressure. So what we would have done? I can't promise you could have survived but early on with a said Okay, give a couple of leaders, he's getting better. Okay, great, Keep going. If he's not getting better, you're not going to keep flogging here with leaders and leaders and leaders of fluid, which is what they did. And so a they're wasting time and be the excess fluid they're giving is going to cause your heart. So we would have had her in early. We would've put monitors on with the scene. We could have sent us to me where she was on this graph, and then we were giving her in a trucks to improve the cardiac output. That and as I said, she passed away, said So with this talk is gonna be about today is the way you optimize not the way but how this works when you optimize that film. And the goal is to maximize the stretch of your heart muscle on improve the cardiac output. And if it's still inadequate, you have to improve the energetic, the bio, energetic, severe heart to get more contraction for the same feeling. And that's what we're So we're going to talk about the feeling part today. So this this lecture is about how you optimize the stretch of your micro party almost with filled. So why is it important not to guess? So here's a well, I just gave you gave it away that I was gonna ask you if you have a sick patient, whether it's the accident merchants department in the wards in the intensive care unit, they've been loads and loads of studies. And you ask yourself, Will this this person who needs an improved cardiac output again? You and I are on the steep part. That's starting her. So we respond to fluid. We are fluid responders. We will improve our cardiocap it with fluid. But I don't know about you, but I'm feeling pretty healthy, so I don't need an increased cardiac output. But if I was sick, if I My urine output was down, was low. If I was at a low BP, if I was confused or tongue did If I had blue legs that were modeled, you say, Oh, he needs an improved cardiac output. Now you want to know, Is fluid gonna be the drug? Is that gonna do the job? And if it's not, I want to know that And it turns out that if you look at loads and loads and loads of study that looked at, do people who are ill severely, oh, respond to fluid or not, it's about 50% respond, 50% don't. So what most people do without even realize yet they put their hands in their pocket, they pull out a corn, they flip, it may go ahead or tails, and we'll be right half the time. It will be wrong half the time and hopefully well, at the end of these two lectures today and the next one will be able to make a more educated guess, as opposed to just guessing. Okay, before we can actually understand how you can make an intelligent guess as to whether someone will respond to fluid or not, you might wanna you have to understand the physiology of pre load and venous return. So, um, this may sound a bit factor is a bit silly, but here we go. I am in as you as I told you, some of you least I am actually right now. I'm speaking to you from my small apartment in the French Alps and were high up in the friend shots and there's nothing here. So when I go shopping for food, I have to go down the valley to a supermarket. And when I line my food, um, I'm at 807 m. There's my wristwatch with my ultimate on it. And when I lose my car up, you can see that's a bag of lettuce. So you might say to yourself, What does the bag of letters have to do with this? To talk on starlings? Low of the heart. Well, look at the size of that bag of lettuce. That's at 800 m. Okay, so and I drive home and home is here. That's where that's where I am right now and those next myself with two friends. And this is going to go straight What we mean by the concept of transmural pressure. So now when I opened the car and I take out my groceries, look at the size of that bag of lettuce. Now. Now, why is that bag so much bigger than it was when I bought it? Any idea feel free time? You eat yourself. If you do want to answer it, is it high partial pressure or CT on. You know, partial pressure over Well, it's written. Could be the ventricular contraction. None of this is lettuce we're talking about not eventual, right? Is it the did, um, pressure change? Yes, it's because the outside pressure has dropped because where the altitude and the pressure inside the bag, I presume, have has not changed. So accounts isn't the pressure inside or even the pressure outside. It's the difference between the two, and that's what we call transmitral pressure. Okay, it sounds very simple, but it's actually very important. And so that's what about, and that's that's using boils. Law boils. A lot of gas is okay, so the transmitter pressure the difference. The difference is what counts between the inside the outside. So either you make the pressure inside higher. But we didn't. You made the pressure outside lower. We did buy going to altitude. So that strength is the wall of that bag of lettuce. And what are we trying to say here with starlings? Lot of the heart. Very simply. If you have a sarcomere, you know, unit of muscle, you've got acting and you've got my license and the acting fibers are car car so overlapping and what what causes the contraction is the link between the action of the myosin immigrated the linkups, the stronger the contraction. So I stretch a muscle. You see, I'm getting less overlap and then I do more. And now I've completely reduced the overlap. So I'm gonna get the maximum contraction. If I keep stretching, it won't make it. Any contract will not be any stronger. So this is what we're talking about. We talked about starting slow the heart, looking at it from a purely theoretical point. So we have the greatest amount or the least amount of should say, the least amount of overlap between actinomycin bridges that have the maximum amount of linkages between accident. So what happened was Starling was working with a group of physiologists at the end of the 19th century beginning of the 20th. And they knew from quite a few years that if you take a piece of thymus Oh, and you put it between to strain gauge is and you stretch it. This thigh muscle will contract stronger and stronger as you stretch it more and more into a to a maximum. The problem with the heart was that you can't stretch your heart like you can a piece of, you know, fine muscle. So it's Starling. Did was You want to know the volume of the heart which would correspond to stretching the muscle fibers. Uh, we would also cause the same strong contraction. Now, in those days, you couldn't measure the volume of the heart by using isotopes. So what he did was very simple. He put a heart in what they call the bells cardio. But what it is, basically is a bath. And if I want to know what volume you take up, I would feel a bathtub to the top and I put you with it or put myself in it and look at how much water is displaced. That's our committees principal. So the water that's displaced will equal the volume that I'm taking up in the bathtub, and that's exactly what he did. And so, as you can see, the the the fluid the water that was proved out by the slowing of the heart was dropping down below impression on a piston that was attacked, a smoke drum, and you could see the volume on the right hand side so he could address the volume of the heart, make it bigger and smaller, and they could see it could see things like cardiac output, BP and CDP under those controlled conditions. And you could see that the bigger the heart was swelling with fluid, the stronger the contraction. And so he was basically saying that the increase in this case BP was determine by the CP if it if it was, if you control that. But this is a big but his heart. His dogs heart was exposed to atmosphere pressure, No, your heart and my heart or not exposed to atmosphere. Where do you have our heart in our test? So we're surrounded by the pressure in our thorax, and that's important. So if you look at starlings curve in a very, very, uh, theoretical way, you can see that's your overlap of your acting fibers. They're crossing, they're overlapping. And as you fill the heart, you're starting to stretch those fibers apart. So you're getting less and less over laps or stronger contractions, he said, because you getting more link up in mind until you get to the very top of the curve and you've maximized this stretch, so there's no more overlap. So you you're going to get you're not gonna get any more contracted by stretching it further. And that's means you're the top of your curve. That's how that's really what's starting strips hold out. Very simple. Really? Okay, so let's talk about intrathoracic pressure. So when you're breathing quietly is anybody you know? And they take a guess that what? You're interested Rast Pressure Interactive. Your pressure is when you're breathing in and breathing out quietly, spontaneously, get 22. It's a big part. Twin nature. Um no, no, no. So that's so That's good. So when you breathe in your brain, you're sucking urine, so you're creating a negative pressure because you're stuck in urine. So it's about 10 minus three minus four minus five. When you breathe out and you expired, you're gonna be to zero. Now if I if this like it's very boring and you're yawning Oh, you know might go two minus eight minus 10. Let's say if I give a cough, maybe plus 10. So the heart throughout your entire life has been exposed continuously to zero in my eyes. Three minus five. Okay, so something like that. And that means your heart is exposed to those pressures. All right. And that's important. Because if I've insulate you, that is so unnatural physiologically because I'm gonna be surrounding your heart now with very, very strong positive Pressure's looking that in a second. Okay, so let's say I'm blowing a trumpet, and this is what we call a valsalva maneuver. And if you don't believe this next time you go to a mirror in your bathroom, put your thumb in your mouth. That blows hard as you can, is if you're looking at trying to get going on a trumpet, look at your neck. Things that all stand out okay, And that's because you're squeezing your heart with that's intrathoracic pressure. Any idea how high you can raise your intrathoracic pressure if you blow in a trouble? If you do a valsalva maneuver in the idea 30 25. Okay, that's good. So I 1 50 wow, pretty high right when I was a kid and I wouldn't be too corny about this Eye is in the States in the sixties, um, one of the games we used to play, and this is probably explains about the way I am today. Um, we used to basically bare down to a valsalva maneuver to it passed out, and we wouldn't pass out because we lacked oxygen. We pass out because we weren't getting venous. Return to her heart and we'll see why in a second. Okay, so let's look at this cartoon. So here is if I take a syringe and I fill it full of air and I put a red cap on it. So no, no district that know they are to leave and I try and squeeze it. Can I squeeze that syringe? Connect can compress center? No, Try again. Yes, you can. Yes, yes, you can. You try it yourself. You can compress. There's long as you have that income co capped. So you have compliance. You can increase the pressure, but you'll get a reduction in volume. Okay, so it's compressible now. Let's see. I do the same thing with fluid. I feel that same syringe with water or whatever food would you want and I try and compresses. Can I compress it? No good. You can't. It's not compressible. It has no compliance. So there's no change in volume with a very increasing pressure. So your heart is far as I know. It's probably full of fluid, not there. All right, that's important to remember. So let's look at these cartoons. So I've got explain something before we start. Whenever you measure a pressure, you always have to measure it in reference to something else. What I mean by that? So let's take this example. Here's somebody's Thor X, and there's the cartoon of the heart and I'm gonna put a catheter into the next game. And you see, this is in patients in the wards and the intensive care especially, and you slide a catheter from a see the internal jugular into the superior vena K. But we're into your atrium, but into your heart. Let's see. Okay, Now, the thing is that the pressure you're going to see is going to be You have to do it. We called zeroing it. You have a transducer and you open that transducer toe atmosphere. So atmosphere is your zero. So the so if you you have you have zero is your starting point. And now if you close the transducer and it's connected to the inside of your heart, if it says it's plus five. That means it's plus five relative to atmosphere. Okay, but we're interested in is what? What is the transmitral pressure? Where is that stretching pressure of your heart? And the problem is, as you saw with the bag of lettuce to know what that Transmitral pressure is, you have to know what the inside of the heart's pressure is. And we know it's five compared to atmosphere, but we don't know if you want side. The pressure is no Ms Work to knit. Zero. Okay, so what is a transmittal pressure of your heart? Oh, so anybody want to guess what is a transmittal pressure but the standing pressure of your heart? That's going to determine how strict your heart is in this example? Nobody. Okay, let's fight No very good. Its plus five, that's that's That's the transmitter pressure of your heart. Okay, so let's say now I'm blowing on a trumpet. But before I start blowing on the trumpet, um, the pressure of my heart was plus five. Okay, just like on the left. But because, like, the syringe full of water, if I'm squeezing the heart just like you're squeezing the syringe, you can compress it can only raise the pressure. So if the inside of my thigh or exit I'm blowing on that trumpet, it's plus 1 50 and I'm already starting out with plus five. That's 1 50 plus five is 1 55. Agreed. Now my CDP, measured from the outside, is gonna be relative to zero to atmosphere, so that's gonna be plus 1 55. So what is the transmittal pressure in my heart now? It's going to do no transmural standing pretty, my heart. The difference between five inside. Great. That's good, really good. And the reason that's important is because some people would say, Oh, that means the heart is getting really full because of CVP is so high. Well, no, it doesn't mean that because we don't know what the intrathoracic pressures. And, for example, if you I can think of a couple of examples where you'll have a very high CDP and yet a heart that's not over full. For example, if you have cardiac temple, not you're squeezing your heart because the pericardial sac is full of state blood or, if you have attention pneumothorax, you're squeezing the heart because gas or air or gas is collapsing. Know long and squeezing the heart. So approved I'm trying to make here is that by looking at the see me pee alone, you don't really get an idea of how stretched your heart is. You can have a very high CCP, and you still have a heart that's under filled. Doesn't mean your your heart's overfilled. Okay, Does that make sense? Yes, it does. Thank you, Doctor. Yes. Um, the descending pressure, the heart and these two examples is the same. There you go. Two bags of letters saying Okay, so let's look at another cartoon. There's your plus five again when we started with Now there's something called You know what? You heard of Valsalva maneuver. That's when you're bearing down and trying to blow as hard as you can. But there's another kind of pressure. You can get it right, and that's called the molars. A NuvaRing doesn't matter the name, but basically, if I if I have seen this several times my career, if somebody has seen endotracheal tube or tracheostomy tube and they're trying to breathe and suddenly gets blocked off with a blood clot or a clot of sputum or whatever or Or they're basically they're trying to breathe, but their tongue is falling back there, sucking hard. You're trying to suck as hard as you can, and you're creating a lot of negative pressure. Not positive, but negative pressure this time. So any idea how much negative pressure you can generate? Maximum. Take a guess. Minus 100. Good man. Absolutely right. So it bends outfit. You are, of course, but yeah, minus 100. And that's in fact, if you ever have somebody who has seen myasthenia gravis, one of the things you can test to see if they're getting very weak, it's a look. How much Megan pressure that can it is. Listen, I think it's 40. Then you know you're in trouble. So about a minus 100. So now let's guess what do you think the distending pressure of the heart is? The stretching pressure and the heart is on the right. What is it gonna be now? 94? It's funny. Everybody says that. Zero. I'm sorry. Is it seal? No, no. Zero. What's that on the inside? No, minus Ah. Minus underneath. Good man. How it might. It's wonderful. I don't Well, sorry. It's plus 100 5 minus. It's 100 5. Yeah, it's only everybody gets that wrong. It's plus find on the inside and it's minus 100 the outside of the differences +105. So it's going to really a stretch heart. Now that happens. I've seen several cases like that. And what happens when that when you see that. So these are not a big bag of that. That's okay because, yeah, it's like going to altitude, right? That's that can create. We call negative pressure. Pulmonary edema. What is that about? Well, your heart will now be very distended in theory, but your heart's full, very strong, thick muscle. But the other objects with the other, um, things in your thorax. That, or not very muscular are your pulmonary capillaries. As you can see, there's a stretches, a radio expansion of those capillaries. If you look on the right, that's a electromyographs microgram, and you could see the capillaries literally ripped apart because it's being so stretched because it's not thick wall, and what happens is you're they're going to get red cells and you're gonna get protein. You're getting fluid pouring into your alveolus and you get a next rate. It looks like this. And I've seen several cases like this, and we even wrote a report once because in the literature they when you see case like this, they say, Oh, we gave frusemide you know, diuretics to get water off of the paper because they have massive pulmonary edema. You get really? It looks like pink champagne pouring out of your mouth because just flooding with no head cells and Protonix is fluid. So it looks like pink champagne pouring out. And what people say is, Oh, it's permanent demon from heart failure. No, it's not from that. You don't need fruits in mind. We wrote this article saying, It's not frusemide you need, It's CPAP. It's positive pressure, ventilation. Okay, so let's go on to another case. Here's a guy. He's a young man. He's been hit by a car and he's taken to the accident Surgeon Department, which is just outside. He's been just outside of the hospital. This is a major case, okay? And he's got a fractured femoral shaft, so you know, he's got a couple of leaders of blood in his thigh. His abdomen is distended. He's probably first a spleen, so he's probably got a couple of leaders, or at least the leader of blood in his abdomen. So he's got lots of blood inside. Okay, he's starting to be resuscitated. He's just got into the office. He's just got into the hospital. He's starting to be resistant with crystalloid solution. He's an agonies young man is absolute screaming in pain and you're calling person, so you decide to get him some morphine. What might happen? It will be a reflection. Yeah, absolutely. You might crash his BP. Now the question is why? Okay, because you were depressing the control center in the brain potentially know with the, uh, well movie, Not Yes, yes and no, that's a little bit in direct. I'm glad nobody's said, by the way, that he may stop breathing because one of the best ways to keep your breathing is being in pain. It's almost impossible to stop something breathing with morphine as long as you titrated to pain. If you give it beyond the point of having no pain, then you may stop breathing. But that's not a problem with this guy. Is there something to do with the site? is something to relieve. The headache from last clinicity gets absolutely absolutely because he's got kidney bleeding. Well, yeah. I mean, that's that's why he's latching while you. But But whoever said that your vasculature is the problem is absolutely right. So let's look at this. So we're going to start by explaining a few concepts. Have you ever heard the term that means systemic feeling? Pressure? Is that does that? Does everybody know what that means? What? Does anybody know what that means? No. Okay, great expert, because you're gonna learn something really new today. It's absolutely vital. So, um, if I we've done this in intensive care by the way doing this would register residents. If I put a catheter into your radio artery, What we do routinely to look at BP continuously and we have on the screen, it'll say 1 2081 2080. And the curve is bouncing up and down. 1 20 Stock 80. Disguise, Doc. 1 2081 28. I also have a catheter going into my internal jugular vein into my right heart. And there you have the CD pee Normal, your CT people quite low. But serotype those two plus three. It's not high. Some people think it's high. It's not from behind. It would be zero to say two. Okay, so the two curves on the same screens. We will have these these values on the screen usually, and they're going 1, 2081 2080 and 2323, bouncing a longer, you know, the to curves. Now if that patient is going to die. We've done this before where someone who you know was going to die, come and their heart stops. So now they're did. There's no flow. All the pressures are going to be equal because don't forget it. And this is an important concept on this planet where there's gravity. If you have a difference in pressure is, you know, high pressure or low pressure. You'll get flow if the higher the grade into pressure between the high and low pressure. So the higher the grade E in the grave with radiant more flow you get. If there's no difference in pressure, there's no Grady int. You'll get no flow. So this dead person, the heart stops pumping the pressure on the arterial side that said 1 20/80 and the pressure on the CBP said It said, say between two deer to 03, they're now going to be equal because there's no flow. You agree? Yes. Yeah, And if you could measure any point in the circulation any point, they'll all be the same pressure. Because they've got to be equal cause there's no flow. There was flow. The person's not dead. So there's zero flow, all pressures or April throughout the entire circuit, from the arteries all the way back to the veins. Okay, so what happens now? So what do you think the pressure is going to be when that person dies? So I'm looking at the arterial tree, and the person has just started. What's it gonna be? 80. Mm. You've got someone who's dead with a BP of a day. It's zero, right? Yes. Everybody agrees. Right? You're dead. You're right. Yeah, my finger roll. That's surprising. All people don't know this. So there's you go. There's your blood picture on your your C 1 20/80. There's your central venous pressure bouncing along, and we're going to stick a defibrillator on this person, and this is an experiment. But we've done this before where people that we knew were gonna die. There's an interesting model, you know, Interesting experiment. If you like that, prove this point. We've looked at this. So what are you going to see? You're going to see. So what does that mean? Circulator with a mean, systemic feeling. Pressure. The other nerve terminals mean circulated pressure. We'll call the MSAFP. Okay, Circuit met means stomach. Feeling better is when there's no pressure there throughout the vascular circuit. If there's no flow, it's it's it's the pressure. If there's no flow, it's the pressure in the circuit. There's no flow. So what's it gonna be? It's going to be equal, and it's gonna be about 8 to 10. So how do you get pressure in your circuit if there's nothing pumping? And the reason is is because your your circuit is elastic and the fluid of the volume in it is going to stretch the walls. And what we're talking specifically about are the videos and the capillaries, all right, and that's the pressure that is the upstream pressure, that drone's blood back to your heart. So let's look at this so it's like a venous return venous return. As we said earlier, flow venous return is nothing, but Being stern is nothing more and nothing less than cardiac output. But instead of being measure of the arterial and see if the order it's measured at the venous and because they got to be equal, it's a closed circuit. You can't have it more going out that coming back in their equal cardiac output equals venous return. So venous return of flow with people's cardiac output and the venous return depends on the Grady int between the means. Systemic feeling, pressure. That's your upstream pressure, and that's out of your thorax. Okay, that's everywhere outside your so Exelon a whole and your CTP is your downstream pressure. Okay, so let's look at this. So a lot of people believe in correctly that what determines your venous return? Is it your left heart? Because blood, it creates BP 1 2080 and it pushes blood all the way around the circuit till it comes back to the right heart. That is wrong. As you can see in this graph on the left hand side, you had a systolic pressure, and it's starting to dissipate because the resistance, the blood flow, all that energy. If you want to call it that, that's what you want to call it. It's what it is is being dissipated because that blood got to get through the high resistance of arterials. Your arterials is where most of your resistance takes place. So to get that blood through that resistance of the arterials, it's gonna lose a lot of energy. And so your pressure drops. So the upstream pressure. And don't forget, I keep repeating this cause it's so vital to understand this. For you to have flow, you have to have a high pressure going to a low pressure graded. The greater the grading, the greater the flow, the smaller the gravy in, the less the flow. Know Grady in't. No flow. All right, so you're up. Stream pressure is not your till pressure. It's your mean systemic feeling pressure, which is located in the walls of the capillaries in the videos, all right, and your downstream pressure is your CTP. Now we just said CT Pete's Treacher's your heart Next that contraction heart at the trends. How much your sock, um, ears or stretched right so your CTP can see has to kind of rules, isn't it? So what? What happens here? There's your great aunt. There is your grade and causing flow on the floor talking about saphenous return, and that depends on the difference. The Grady int between your mean systemic feeling pressure that's the stretching of the walls of the capillaries in the videos and your CPK. And so there's where your stomach feeling pressure is, that's your upstream pressure, and there's your downstream pressure and you can see the grading is really very small. And so one of the ways you can determine it's not easy to determine. But if you were to try and determine what is the means stinging feeling, pressure, well, if a patient's dead and you see all those pressure's equalizing, but that's the pressure of the artery. But that's the pressure in the central vein, and it's also the pressure that you can't measure directly. That's the pressure in your capillaries because there's no flow. Every example. Okay, so it's like saying right Ontario pressure, as in So I could have said that before. Steve E P. Colon cancer purpose is equal to the right atrial pressure. Okay, so we saved ready to a pressure. We're talking about the CP. They're essentially the same. Okay, okay. So let's now talk about something really important. That is what is How do you determine what determines what determines this means? Systemic feeling, pressure. That's the upstream pressure. What determines that? So I'm gonna ask you to do a phone experiment with me. So has anybody here a Zen? Anybody hear anybody not slept on an air mattress here? I have. Okay. I think most people I know stuff that they're marriages. I spent a lot of my life on your mattress is unfortunately. Anyway, when you open your mattress up from a box and it's stretched out on the floor, as you can see here, there's completely flat. And if you were to measure the pressure in the air mattress and we'll call that the equivalent of the mean sustaining killing fracture, there's no strength in the walls of the images. And as somebody once said to me during one of my talks, they said, You know, you mean it's not bouncing. I go, Yeah, that's the word bouncy. So there's no bounce to it at all, So you start filling it up right, Okay. And as you can see, that's all collapsed. Now, as you feel that airmen tress, it's kinda assume it's full ship. It's capacity for, But if you try to sleep on it at that point, you can cause you're collapsing corrects the floor because, as you know, with an air mattress, once it takes, it's full of shape up. All that volume of gas that you used to fill up the air mattress is just basically distended, but there's no bassinets to it. So if you try to sleep on it, you're gonna like that guy. You're going to go right to the floor, and if you make the pressure on it, it's zero is still. That's why it's not supporting his weight. So there's no stress in the walls. Walls of this elastic air mattress are not being stretched yet. Okay, so you filled up their mattress with Volume two full the shape, but there's no bounciness to it. So all that volume is what we call undressed Volume it hasn't stressed. Restrict the walls of that elastic. They're mattress. Okay, now, if I keep filling it No, The extra vial put into it doesn't came for the shape of their man interest, but it can support the weight of someone is quite heavy, because now the pressure inside it is high. And that's in this example. The means stinging feeling. Pressure is say in this example suppose eight. And you can see that the walls of the air mattress for stretched. And that means that they they create pressure inside and all the volume you've added to that air mattress when it was at its full capacity but wasn't bouncy. Everything you add to that afterwards makes it balance your balance here and bounce. Here's what gets really tight like a drum. Very bouncy. And now you can sleep on it. And all that extra gas you put into it is what we call stress. W That's a really important concept that you all understand that. Is that okay? Yes. Thank you. Okay. Does anybody not understand that? Just thinking about going back to the dead person. So if you're saying mean system me, quitting pressure is cereal. They didn't say it was zero is. I said it's unstressed. No. Well, no. The point is that this dead person okay, you're in some ways, you're right. if the person had lost blood and I'd stay. Yeah, but this person had lost blood. So when they stop, their heart stopped pumping. The blood that was in the circuit was there was some stress volume in it. And that was the interesting film pressure. But if they had lost blood, then you have been right. So they still had stress volume in them. But they're just the heart wasn't pumping anymore. So this is what I'm saying is you don't have to have circulating blood to stretch the walls of the air mattress. Okay. It just has to be enough blood to fill the air mattress or the or the vascular system to cause stretch. That's the stress. Morning. All right. Yes. We'll come back to that in the end, if you want. Okay. It's not a problem. So, uh, let's see. Let's go back to our gentleman who have the broken leg and the ruptured spleen was in agony. And you're a kind soul, and you're giving him something to ease is pain, and you give them some more feet. We were right to say that the, um they may suddenly crash your BP. So why would that happen? Well, for this reason, let's say we talked about the air mattress. Okay, let's say magically, I could make my air mattress twice a big so I I filled my arm. Actress. It's got It's very bouncy to the street is on stress volume, and they're stress volume that's made a bouncy and let's see magically, I could make my air mattress twice a big Well. The stress value is going to then be converted into unstressed volume because it's gotten bigger, so it's got bigger capacity, so you're gonna lose the bounciness. On the other hand, if I had an air mattress that was kind of bounces not to bouncy, and I suddenly made the size that magically could make the air mattress half the size Well, a lot of the under stress volume is going to become stressful. I mean, it's gonna get really tight, really bouncy. Does that kind of makes sense to you? That's quite important concept. Yes, it does after, Okay, so let's say the man who was in pain, we've given the morphine and for several reasons, Morphine's a direct, you know, dead later, it also releases histamine, and you've taken some of the pain away and that remove some of the sympathetic drive you're going to suddenly make that a Ramat tress bigger. You're going to dilate the veins. And I like instead of saying I personally don't like the word vasoconstrict vassal dilator, I prefer a precise and saying vino dilator. In this example there are arterial dilators, but they're also vino of dilators and often vena Oh, dilators of the same drugs. Arterial Doppler is just in a smaller dose. So if you vinos dilate this patients, um, venous system, the videos, the capillaries You're gonna make the air mattress a lot bigger. You're converting, you're altering, You're converting stress volume unstressed volume, and he's lost a lot of Lyme to start with. So we so obviously you know, not got to play with. And you're going to drop the mean systemic feeling pressure. So the Grady int is going to drop and his venous turns going to drop his venous return drops the bloods not coming back to the right heart. The right heart's under filled It can't pope as much blood to the left heart, so the left heart gets less blood back to it and then it pumps less blood out to the arterial system. So you create less BP. On the other hand, if you were to give him a venoconstriction, you make the air mattress suddenly half the size you're converting unstressed volume to stress volume and you're going to make the air mattress bounce years. You're gonna raise the mean systemic feeling pressure. And so not gonna increase venous return. Okay, and something that's not often appreciate it. And there's been studies that true this quick nicely that, um if you take a wall of the vein or video and you take the wall of the artery, the video will have five times more adrenal receptors and the arterial side will. And when you think about it, it makes absolutely perfect sense because we've evolved to basically keep ourselves alive. And what killed are great great great great great great ancestors. Back on, the savannah was being bitten by a saber tooth tiger and bleeding to death. It wasn't alcohol related illnesses. It wasn't smoking related over. It says it was bleeding the day. And if you think about it, if you were to engineer a human being, you'd want a system that said, Okay, do you lose blood? As soon as I start circulating a few, uh, a bit of adrenaline or jenaline. I would like the most sensitive part of my circulation to be That constricts my veins, which makes my air mattress smaller, which will convert unstressed, a stress volume which raised my immune system. It filling pressure, at least temporarily, and we'll maintain my venous return in my cardiac output, and that's what we do. Okay, so if you have somebody who is somewhat hypovolemia like the gentleman who might have been low in volume, you've got to be very careful if you give anything that can cause vinos dalati from, like opioids, sedatives or glycerol time in a trade or anything that will do that. And that's the reason. Now try to avoid too many curves, but I think you need to come across some. You all know about the Starling card, which is showing and talked about, but you want to also know about what they call the venous return or Guyton Curve gotten was the man who describe this as Starling was the manager scored Starling hurt, and so you can see here on the X axis, you have central venous pressure. We're right at your pressure that the same on the Y axis. You have venous return, which again is equal to cardiac output. So it's a flow. It's a pressure on the bottom flow on the on the Y axis. And as we said, mean systemic. Venous return equals the difference between main systemic feeling pressure and see a. The greater difference, the more flow, the more venous return. And so if you drew a graph, it looks like this. So as you raise your CTP, if your means sustained feeling pressure is is is unchanged. As you raise your CTP, the grading gets more so your venous return reduces. It reduces and reduces until it's zero. And when it zero. We just said that when there's no flow, that means your mean sustaining feeling. Pressure equals your CD. And that's one way, which is very experimental, of determining what your meats needed. Filling pressures. It's when they're CPI is equal toe mean sick feeling pressure because there's no flow, Does that Does that make sense to everybody? He had a big sense. Yeah, okay. It's an important graft to know. Okay, And that's just a cartoon of what? The Grady it would look like, You know. See, we're going to modify that. No. Can you modify the venous return? Curved? In other words, can I increase the mean systemic feeling pressure? Can I increase stressed volume? Okay. Yes, I can. Two ways. I can do it with an air mattress. I can do one of two things with my magic. Where? Mattress. Okay, I can either pump morgue ass into it so I can move. Increase the feeling. Or if my magic, I could make the air mattress smaller by creating or converting unstressed volume to stress volume that will raise the meat stinging feeling, pressure. So what would happen if I did that? Let's look at that. There's your CTP and there's a venous return of those red dots. If I either venoconstriction, I made the air mattress smaller, so I've converted unstressed a stress volume. So I've raised the mean stick feeling pressure or for the same volume I've increased started. I mean the same capacity of the air mattress. I pump more more gas into it. Then you're going to shift the curve to the right and your mean systemic feeling. Pressure is going to increase. That's what happens when you either fill somebody more where you give them a small dose of venoconstriction. You've increased the main systemic feeling pressure and you've increased the venous return. You see what happens here? You've increased the grading, so you get more venous return. So we've already looked into starlings for and we've just described GYNs curve and both these curve work on the same heart. So they're gonna have to meet. We have to work together. They're gonna have to, you know, how do they work together? So first thing is, we just said cardiac output and venous return are the same. So they actually is on. The graphs are gonna be the same. They've got to be equal. So I'm just repeating myself because it's so important to understand that just measured at different points in the circuit cardiac output neck and the arterial side bs return on the venous side. Central venous side in a steady state, your CTP is going to be at one point it's gonna be the same output and return. You're gonna look at this. So here's we're starling meats. So we got our central venous pressure on the X axis and we have flow and you see the cardiac output or venous return because they're equal. That the same thing on the Y axis. So there is your venous return curved, which we looked at earlier. Just now, that's your guiding curve. There was a mean, systemic feeling. Pressure. That's when there's the equal. There's equal CDP is where there's no flow. There's your card, it helping curb your starling curve and your equilibrium point. It's gonna be right there. All right, now, let's see how this works. Let's say this is someone who's got That's, um this is, um, May So we're on the steep part of our starting curve as we sit around here. So this is someone who is going to respond to fluid if I gave him fluid by increasing the cardiac output. So if I were to give you more blood or I would've venoconstriction you say a small dose of Nora Dremel in, I'm going to shift my right and curved to the right, and because my my heart is healthy, it can accommodate that extra volume that's getting for venous return, and it can pump it out again because it's got reserves. Got energetic reserve. So it's going to increase my card ago. All right, so you can see on this graph the CV pee increases a little bit, but the main systemic feeling pressure increases a lot. So the Grady into Don't forget it's not. The absolute number is the grading between the two is gonna be in favor of the main systemic feeling pressure. So your heart is responsive to volume and when it meant mean stink feeling pressure increases more than the CDP. It's got more than CDP. You'll get an increase in cardiac output. Okay, there's a big difference with attention, so both will go up. But the greedy it will be increased because there's more greater increase in your stomach feeling pressure than CDP. Now let's say you have somebody who's a heart failure or the lady that we so right in the beginning, who was given all that fluid and did not respond, okay. And what happened to her probably was they filled her or they've, you know, constrictor. But in her case, it just filled her and filled and filled er they're going to shift the curve. The venous return trip to the right. But because he's on the flat part of her starling curve, you're going to get an equal increase in CBP to the same increase in the systemic feeling. Pressure hence, Grady Int didn't increase. There was no increase in cardiac output because the heart couldn't accommodate the extra blood it was getting. So you're going to get a rise, a big rise and CDP for unequally unequal rise. It means stealing, feeling pressure. There's no difference. There's no increase in Grady. It's the Grady in that counts. So you're gonna get the same venous return, but at a higher pressure. And there's going to be no increase in cardiac out. And interestingly enough, if you were to look at the other side of this, the magnet have somebody in heart failure. One of the treatments of heart failure is to give vino dilators. So if you ever get somebody in the accident emergency department and they're very breathless and they have acute pulmonary edema from heart failure, what you can do and you ought to do is give vino violators, whether it's morphine, PTN or whatever you're using as a V know done later, and diarrhetics. What that means is that it's the exact opposite what we just saw because you're on the flat part of your starling curve, you're going to shift that little gray dot to the left, and they will not be a drop in cardiac output. Just gonna reduce the pressures. And that's what you want to do because it takes the pressure off the lungs, so you're going to get less from redeem A. But you won't drop the cardiac output unless you keep taking more and more and more fluid off until you get to the steep part. Then it's gonna drop. Okay, so they're both equally increasing, but there's no increase in grade IV, and this is what I'm saying. If you have somebody like the gentleman who had the broken leg in the ruptured spleen, if you were to be no dilate him or decreases blood volume because you've lost blood again, the venous return curve now will shift to the left, not to the right. And so what happens because you're on the steep part of the starting curve you're gonna get dropping means stinging feeling pressure, and you're going to get a drop in cardiac output and then BP. Okay, so it's gonna look like that great and decreases. And that means your venous return decreases with means your card. A couple Christmas. Okay, so let's go through a couple of clinical examples here. So what do these cases have in common, based on what we just talked about? So somebody's had a spinal anesthetic. This is a true story, not a story. There's stories that was discovered in the United States. They did a stent, a database. This is where I was working in Seattle, and they discovered throughout the United States that there were a number of cases of young men having spinal anesthesia for relatively bloodless operations, and they had cardiac arrests and they were not able to recover. How about somebody who has, um, poor? We've already talked about this in the first like trip. It will go into this in detail or bit more detail someone who's had, say, pneumonia. And they have very poor oxygen saturations. You intubate them, you ventilate them and you want to increase what we call people positive end experience. She pressure to try and open up those alveolar like balloons popping open to improve the oxygenation and you do. But oxygen delivery oxygenation. But oxygen delivery drops. And lastly, I don't know if you heard of some called a rapid sequence induction When someone is about to undergo on operation and they have, say, a full stomach where they have a test. I know. Obstruction one, they're when they're Nikolay niece, it ties. They're high risk of aspirating castrate fluid that may be forced up into their hypopharynx into the throat because their lungs are unprotected and they release time so they don't have their normal air into your reflexes protecting them, so you want to make that period when they're vulnerable has rapid and shortness possible. So what you do is we call a rapid sequence induction, and that means you give me, uh, agent, that puts you to sleep, get your anesthetic, and you paralyze him so the larynx is open. That's called a rapid sequence induction. And most of the cysts are terrified of cracking the BP here. When they do this rapid sequence induction is we're going to see what these three things have. Income. So pace number one, this was the study. I was saying so what happened was this. This is one of many cases that were It's not that common, but it's coming enough to notice. And it's tragic. 25 24 year old person who's healthy. He's having a knee arthroscopy that's not major surgery, and he's having another spinal anesthesia that basically put a needle into there To the CSF, the cerebral spinal fluid inject a very small volume of local anesthetic, which makes you anus. It ties from the waist down. 25 minutes into the procedure, there's a severe bradycardia and a massive drop in blood pressure and soon followed by a cardiac arrest. Now, bear in mind, this is happening in an operating room where you have surgeons, you have a niece says. You have nurse anesthetist, you have the whole team there and every heartbeat, every breath is being watched on a monitor. So it's not like this. Just discovering this. This is like a controlled experiment, and despite fluids and f a dream and extreme, there's no response and dies despite immediate cardiac massage. That's incredible. I mean, you couldn't ask for a better scenario to save somebody, and they couldn't say these big. The question is why anybody want to take a guess, you know? Excellent. Excellent. So that's the spinal anesthetic will block your sensory nerves has you Don't feel the operation. It will block your motor nerves so you don't move. But it also blocks your sympathetic nerves, and often it's very hard to know how high they are. And most studies have shown that the sympathetic nerves are blocked a lot higher than we think they are. So you're getting vino dietician. And the problem is, you might say, Well, why did cardiac muscle aches when I worked? I mean, you know, this is happening, right? Fun of this whole team. And the reason was, because they're massage your heart that's empty. Can't massage of the heart. You can massage all day, but there's nothing to pump out because the blood's not going back to the heart. What you're saying? Yeah, but they're getting fluids right, because they anticipated this. The problem was, it takes a long time for you to fill up that massively dilated space. Your air mattress has just gotten really big, severe, bouncy mean This has been totally lost. Your mean sustaining filling pressures drop. You have virtually no partic, no venous. Return to your heart's empty and to fill that air mattress is gonna take you a long, long time. You haven't got that long. So what they should have done according to the, you know, hypotheses. What? They should have started giving rapidly giving nor adrenaline because the air mattress to get smaller to basically cause venoconstriction. Okay, case number two So sorry. Here's this is just the explanation. So v nodal taken. Very good. You're converting. Stressed to unstressed volume you are. You dropped your stomach feeling pressure because you're up stream pressure, your grade and drops and your mr no drops. So basically, you're getting this. You're grading plummets because your means stinging feeling pregnant plummets because you've created you converted stress to unstressed for your air mattress has gotten bigger and you've lost all that bounties. Okay, Case number two patients got severe pneumonia in the night to you. Very high pox sick. They're saturations 84% of 100% you decide to give them. We call positive and experience with pressures were trying to pop open like balloons. Those alveolitis start participating and gas extreme. And we went from 5 to 27 years of water. The BP stable, the oxygen saturation increases to 95%. So that's good. Everything is fine. Success correct. Everybody happy? No. Well, it's not because we just changed the number. Well, little over. Maybe I was going to say Maybe. Maybe not. Right. People know what you're You're on the right track. But what's the missing piece is we didn't measure the cardiac output card. It can get scar. Dig up. Okay, So by increasing the pressure in the thorax, we pop open those alveolitis. And we could see the result because the saturation is going up. So we're very happy. Everybody's happy. The nurses air. Delighted. So you increased your peep and increase your PF ratio, which is another way of looking at your oxygen saturation. Okay, It's a fancy way of measuring oxygen saturation, so that's increasing. So everybody's seeing on the screen and were absolutely delighted were so happy we didn't talk about we didn't measure was cardiac Index. And by the way, you can have a low cardiac index and keep your BP. This thing doesn't mean the 2 may be related, but not over. Okay, so in this case, it doesn't always happen. By the way. There are lots of times and you increase people and you improve the oxygenation and your cardiac output stays the same. But in this case, we didn't make sure we didn't say we measured the cardiac output. So in this case, the Cardec in index cardiac output drop. So what happens? The overall oxygen delivery, which is Don't forget, That's the ultimate goal. It drops. So So be careful. So why did that happen? Well, positive pressure, ventilation, we said, like the syringe is squeezing the heart. Don't forget. Your heart is surrounded by pressures of zero to minus three minus five. Normally, all your life, you've been breathing like that, right? So your heart is all your life accustomed to breathing to being surrounded by pressures that are very low. 02 minus three minus five. My cough for a split second. But you don't have positive pressure around your heart. Most of the time. In this case, you're eventually somebody, and you're increasing the picture more and more with this positive on experience. Pressure. So your CTP because we said that the syringe can't be squeezed. It's going to squeeze the heart. It's full of fluid, so it's gonna raise the CDP. If you don't believe that, look in the mirror. When you go to the mirror, Look at yourself. When you do a valsalva maneuver, you'll see your neck veins standing out. You're decreasing the Grady in because your downstream great, it's going up. You mean systemic feeling. Pressure is not changing and therefore you drop your venous return. Remember, we talked about the syringes, right? So you're squeezing and you're gonna raise the pressure in your heart or cdp, In other words, So what happens is this your great aunt gets smaller your means A stinging feeling. Pressure hasn't alter. It's outside the thorax. Your CTP went up since the smaller graded, and here's the last. Well, this is one of the last cases. So this is someone who's got a suspected small bowel obstruction. They're going to go for surgery before they go. We have a look at them. They look kind of dehydrated, taking the operating room for a laparotomy. The missus performs a rapid sequence induction, so it gives a quick bolus of an anesthetic agent, and it gives a muscle relaxant so that the larynx will be relaxed so it can place a tube. We're here. If you can place a tube into the lungs rapidly. The drugs are used of propofol, which is an anesthetic agent. So when it looks like milk and rocuronium because one of many muscle relaxants will be the most commonly used one today and the BP crashes. Now, most instances we'll tell you why, and they'll be half right. But they always always forget the two costs. So what other two causes that would have caused that BP to drop? Anybody have an idea? Muscle relaxant. Okay, start with the first one. It would be the first one. Sorry. That's a good thing. That you? Yeah, but that's okay. So those are the two. The two components of the rapid sequence Induction is too quickly. Give an anesthetic agent propofol, Which is that? The one that looks like milk. And the second one is a muscle relaxant. In this example, it's rock your own. It doesn't matter. It's just a muscle relaxant to relax the larynx. You can put a tube it Well, what is propofol do? Aside from putting it right, I pretension Yeah. Why? Visit Visit on a venue? Yes. Good man. So it's a well, it's a V. Know it's a vasodilator, but most specifically in this example, it's a V know dilator. So you're right. And that's what most people know about. Okay, most of the cyst will tell you that they know that it also has other effects. But that's what we're talking about. Now. It's a mean If it what's the second cause? Patients already dehydrated. Well, that's right. So that means that they're more likely to be sensitive to be no dalati. Right? But the other thing is, rocuronium is a muscle relaxant. Isn't it? Great. So I'm going to paralyze your muscles to put the tube in quickly. The tube is in once that tube is in. What do I have to do now? You're paralyzed. Yeah. So you have to force the pressure yourself like they can respond. They can't contract there. The smooth muscles in the vessel. Yeah. So what? I have to very simply what do I have to do in their place? Because if I don't, they die. No, no, no. If I'm putting if I paralyze you right now, what have I got to do to keep you alive. You're paralyzed, you know, You you got you got absolutely got a ventilator. So what? So there's two causes and is what? That's funny, cause most of this is always forget the second cost. It's very important. So number one you're getting you're giving propofol, which like many not all but like many anesthetic agents, causes vino down on taking. We already said the lady was for the patient was somewhat dehydrated. They convert stress to unstressed volume. They drop their upstream pressure of the words. That means stinging feeling quicker. They drop their Grady into and they drop the BS return. Hence, that's the one cause of a drop in cardiac output and BP that everybody knows about the anesthetic world. Okay, so you get that. We just filled that before, but the other thing, that everybody So there you go. But the other aspect that everybody forgets is you're also gonna be ventilating that if you ventilate. And we said your heart is used to being surrounded by 02 minus 345 for the first time in their lives. Perhaps if you ventilated me, it was the first time in my life, you are going to be surrounding my heart with a lot of positive pressure, cause when you ventilates somebody, it's always typically, say, five plus 52 plus 20. Let's say plus 2025 you're gonna be squeezing the heart. You're gonna be raising the CDP, and you're gonna be dropping the grading from the other end. And then again, the insertion goes down. So talked about squeezing the heart because your ventilating somebody, you and I are not used to being ventilated. That's very unfit. See, a logical. And so what happens there is you raise your CTP. So basically you're getting two reasons to drop your BP on a rapid sequence and look. And these are just examples to illustrate were these different aspects how they work? Okay, here's another clinical case. We're almost done. 77 year old lady. This is a true story. He has what we call a C. Difficile toxic megacolon. She has a very, very serious infection that's causing her colon, her large bowel, to dilate. It's very septic. It was very a dentist, peripherally, that you get with sepsis. He's already received three liters of fluid. Our blood pressure's low, her heart rate's fast, and the response rate is fast. And you're not that slow. So would you agree? We're going to try and do is achieve what we sent over there with effective cardiac output. We're gonna try and optimize your feeling first of all right, we never been to agree with that. If it's not enough, we don't give any trips. Well, good. Yes, we do think it does, Yes. Yeah, you so that now I'm being a little bit provocative. You're okay, because everything I've said so far is like classic teaching. But today they're starting to change their model a little bit. And the reason I'm telling you this is because now that you've understood these concepts, you may understand why this model may be about to kick. So we know that if you give too much fluid to somebody will show this yesterday. The more fluid you give, the less chances you are you have of surviving. We We think that's pretty clear now, okay? It's associated with mortality, and what some people are studying now is, instead of just sustains somebody with fluid alone and again. This is a little bit early days. Okay, So, uh, someone tells you this is not true. And I would I wouldn't fight for this. But I would say this. I want you to be aware that this is happening and there have been more and more studies that have been trying to work on the idea of stressed unstressed volume. And what they're saying is that if someone needs fluid, yes, you want to give them fluid, you have to give them fluid, but you don't want to overdo the fluid. So maybe you could get away with a little bit less fluid by giving small doses vino constrictor doses at the same time. If your adrenaline and what happens if you delay giving nor adrenalin in this study, your mortality increased because what they found was that with every hours delay of giving nor drennen, they had an increased mortality. These were vino venoconstriction doses. Don't forget if I give a big dose in order and I'll get arterial constriction. We're talking about venoconstriction low doses, cause if there's five times more receptors on the venous side than the arterial sites, you need more rest. Does the lower dose so really nor adrenaline. Spared about a third of the volume, you're required to get to the same BP. All right, so what they're really saying is that so Maybe we use a new model. So maybe it's not enough just to get them to the top of starting curve Need we need to give him fluids, Yes, but also get them maybe small venoconstriction doses of your adrenaline. Why? Because, as they say in this study, Nord Reynolds able to redistribute the venous blood from the unstressed to the stress volume. Now, the reason I told you all this is because now I hope you will know what we're talking about. We say converting unstressed distress volume and basically you're doing is you're making the air mattress smaller so you can need less gas to get it bouncing again. All right, it sounds it. It's stupid, but And so, by doing that, your excessive you're avoiding excess fluid, which may worsen the outcome. And one of the ways that worsens the outcome is what we talked about yesterday. And we talked about the glyco. Okay, Alex and the problems with high pressures. So basically, you want to use amount of fluid. You need to get the BP and cardiac output. But if you get away with a little bit less by giving a small venoconstriction dose of nortriptyline, it might be able to convert unstressed the stress volume to make your air mattress smaller and therefore get away with less volume. To get that air mattress balances get means student feeling pretty typical. The insert. Okay, this stuff is Oh, it's going to say his mainstream and I'm not making this stuff. So let's look at these studies. They're talking to 2020 to talk about under stressed blood drawn in 2020. Talking about means stomach feeling. Pressure this here again. 2012 mean stomach feeling pressure there till about stress drawings that means circulation. Feeling pressure. Same thing is means student or pressure. And they're talking about how anesthesia causes V nodal taken, and it's causing stress to on stress volume. And it's the politic explaining this on the physiology. So what I'm taking you're here was something that is actually becoming mainstream now. So, to recap, we said the CPS took to, uh, to recap it to articulate is got two functions one it opposes venous return. Okay, so if you raise it like when you ventilates somebody that will stop venous, return for coming back, and that will reduce your venous return and hence your cardiac output at the same time it distends. It's the it's the bag of lettuce. You remember that it stretches the myocardium. It causes a greater contracted by a car because it's stretching those sorghum years. So it does two things that's going to find that balance between the two. So remember to finally recap the end of the day. The goal is an oxygen. It's not cardiac output. It's not extreme situations. It's oxygen delivery. And we said it earlier on is the first. Like we said, cardiac output smoking the most important factor because it's rapid. Unlike hemoglobin, which goes up over time. If you go to altitude and you're liking oxygen in the air, your breathing or it doesn't plateau. A PSA saturation does. When he gets 100% saturation will exercise. You go where's cardiac output can go with in a clinical 5678 times higher. And of the factors that influence cardiac output, filling is the most commonly one that we won't street. And so that's why it was really important that you understand the physiology of feeling. And so that is all I have to say about that. So any questions about delight to answer if I can help you Thank you so much stuff for the end up to get intriguing session. Yes, there are a couple of questions. So the first question is, by El Dorado, we on. They're asking what you please repeat the relation between intrathoracic pressure and heart pressure as well as C v P. Okay. Um so let me think I could do this, okay? I think the simplest thing for you to do Okay. Can you see me? You can see me on the screen. Yes, he handled. I'm going to do my valsalva mirror. Look at my neck. I hope you can see it. You see what he thinks? Yeah. You don't. You can see it or not. I don't see that you don't better, but could you see? My neck means it's hard for me to see what you can see. Anyways, he can do what I'm doing. My heart is when I'm breathing talking to you. It's probably between zero to minus three. Let's say so. My heart is not being compressed when I blow on my thumb like I'm blowing a trumpet. I am creating positive pressure, my thorax. So I don't know how high it is cause I'm not trained. Trumpeter. Let's say it goes up to 100. Okay, that means 100 centimeters of water are squeezing my heart cause it's being squeezed by the pressure inside methotrex. Right? And as you saw with the syringe full of fluid, my heart's full of fluids. Blood. It's going to not compress, but it's gonna raise pressure cause there's no compliance. And so by raising that pressure, it's gonna be You can see that my neck veins. My CP is gonna go well, and so I'm f c e p going up. I'm going to reduce the grading in between the means steaming feeling pressure, which is outside my door X and my CDP, which is inside like the wrecks and a greedy it gets smaller and because it gets smaller, I get less venous return. And hence, as I said earlier, when I was a kid, I used to do that with my friends until we passed out and we didn't pass out because we didn't have oxygen is because we weren't getting venous return and the hence we didn't get blood going toward brains. And I would not advise doing that by the way, it made it in front of the time. But, you know, we had a strange way of having fun, I guess is that kind of makes sense. Yeah, That means thank you so much. We've got another question by Abdullah on he's asking. Can the heart muscle distended To the extent of temporarily squashing the coronary heart vessels while it feels, uh, as far as I know, No, I've never heard of that. Um, there are a lot of complicates. What What can happen, though, is if your heart is overfilled over distended in the pressure up is too high. Then the Grady in that forces coronary are bit blood. Can be, um, can be lowered so you don't get the coronary flow that you need for your for your myocardium, and that's that could be a problem. So if someone has to say a pulmonary embolism and the right heart can't pump the blood out, it distends And what happens is that you you raise your pressure inside your your your heart and the to get flow Any flow. Whatever you're talking about, whether it's venous return or coronary artery or cerebral artery, you've gotta have a great. And if your pressure downstream pressure is too high because your heart's to full, then you're gonna You could reduce your coronary artery flow and then so you didn't have problems that way. Perfect. Thank you so much, Doctor. Is that any other questions that everyone wants to ask for? Frito, meet yourself. Just one question, doctor, Just to help me on the fun of it better when we were talking about the force that drives venous return, how does end diastolic pressure in here and preload and things like that? How does it sit here with venous return? Uh huh. Yeah. Okay, so, um, we're into a different topic here. So we're talking about the pressure in the atrium because that's where the blood's coming back. When you're tricuspid, valve is closed, it's filling, and you're you know you're in diastole. Then it opens up, and then suddenly everything drops that equalizes. So the pressure in your atrium is suddenly you know, pouring blood into the into the right ventricle. Um, I don't know what else to tell you, because it's really a play. An interplay between the mean systemic feeling pressure, which is the distended videos, a capillaries there creating that that you know that that stretching pressure and the right atrium, which is where the venous return goes to. I think that's that's preloaded. Basically, was pretty low. It's not your right, Prilosec. You distinction of your diet, your eventual in diastole. So it's slightly different. Does that help Abdullah? Sorry. Okay, okay. Yeah, he's saying yes. Perfect. Is there any other question that in your words, to ask before we do give it a rap? Um, so we've got one question by J. Potato on. He's asking what happened with the 65 year old woman. If they gave you a low read instead of crystalloid, might she survive? Uh, it not Because the problem was the whole point is whatever fluid you gave she was not responding. So all you did or they did. It was waste time way. Think what she needed. It was a nine a. True to improve her cardiac output because the feeling wasn't doing it because he was on the flat part of her starling curve. So whatever fluid they gave would have probably done the same. Perfect. Thank you so much. One most question list. Um, I'm going to, uh, meet yourself, if you can ask your question, please. Yes, Doctor. M, when I make sure the venous reten on the cardiac are pooch, do you consider in case off the CardioMEMS memo party or something that is that affect the muscles off the heart in case off the venous return or venous uh, put. So I didn't quite understand that when you are just causing the measure in the output, the venous return or videos, I'll put yeah, on the cardiac output. Yeah. When you have cardiomyopathy or cardiomegaly do what do you consider all that particular disease that affect that Moses off the heart? Yeah, course. I think we don't really make your venous return. We measure because Venus turn equals cardiac output were more likely to make your cardiac output. Um And so yeah, Anything that will influence the ability of the heart to inject the blood it receives the words venous return, whether it's a myocardial infarction, whether it's my card itis or any cardiomyopathy. Yeah. And so, for example, if some one has, um, a congestive cardiac failure, which is a form of cardiomyopathy, they're on the very flat part of starling curve, as I showed you earlier. So if you give them fluid, all you do is increase the pressures which are reflected in the lungs. But you don't increase the cardiac output. So you have all these, all these different parameters. When you're actually analyzing this, it's I'm simplifying this a lot, okay? But you you have to take into account All these different factors are a lot more than we didn't talk about tonight to try and get a handle on all this and that that's that's all. But this is a starting point. Really? Well, I find very surprising is that so many medical students and so many doctors I know I have no idea about this. And I can understand why, because this is a very basis of everything we're doing. So it's a starting point. It's a foundation which you're building your house. Okay. Perfect. Thank you so much. One last question. Is it better to use a Tom in eight instead of propantel propantel fall. Sorry. Broke propofol. Yeah. Uh, okay. Yeah. You have asked the wrong guy about that. So I don't want to bore you with a very, very exciting story, but, um, Etomidate was the one drug I would never use. Why? Because etomidate has to fact fix that one. That's positive. And when it's very, very negative, the positive effect is that it tends not to cause cardiac pregnant or, you know, validation supposed to. The bad effect is it's the most potent inhibitor of cortisol production known to man. And I was involved indirectly discovery of that. And we saw a lot of patients die because of etomidate and that really, that really colored my view of etomidate. And there are so many other ways. One of the simplest things you can do is if you have somebody who you think it's very, very fragile and you're afraid they're going to drop their BP. You can do one of several things, but one of the simplest things you could do is just give him a small injection. Very dilute venoconstriction before you start, because you have to anticipate they're going to be no, and you do that, you'll be okay. There are a lot of tricks you can do, but that's understanding the physiology. However, what I was trying to tell you as well was that so many so many nieces I know will be obsessed about the vena a dilatation side of there. Rapid sequence in dokie. But they'll totally ignore the ventilation side of it's. Once they put the tube in, they say, Oh, he's okay. The BP stayed up cause I use whatever drug I used. But then then forget that once they start ventilating, then they see the BP disappearing. They're surprised. Well, it's because they didn't take into account the other side that the raise the rise in the CVP they don't really you know, they understand the whole does he already behind this? And that's what you do now, I hope. Okay, everything too So much, Doctor Bagel. Thank you for giving up your time to pride us with the session today. I think we're all highly enjoyed the Sachin. Personally, I kind of enjoyed and understood the graphs in terms of understanding the concepts now, in terms of one next session, it will be tomorrow at 10 o'clock in the morning with Dr Roy on, she will be going over epilepsy. So thank you so much. I worked for attending today. Session. Thank you so much, Doctor. Go on. I will see you in the next session with you. Take care, everyone. I'll keep the chart open for some time. In case. Um, I really didn't get the chance to fill out the feedback form. Otherwise. See you tomorrow. Okay. So take everybody. Thank you. Yeah.