Vital Signs are Vital: Heart Rate

[music] Welcome to the Critical Care Obstetrics Podcast. My name is Suzanne McMartry-Baird. The Nursing Director at Clinical Concepts and Obstetrics. I'm joined today with my partner, Stephanie Martin, Medical Director at Clinical Concepts and Obstetrics. We're so excited because we're going to start talking about one of my favorite topics. We're going to do a whole series on vital signs or vital. So this series is going to break down each vital sign. But we'll go into more about some of the vital signs individually. And don't forget, we do cover this in our academy with more examples and throughout the different pathologic disease processes and give examples in more detail in the academy. But this is just to highlight the individual vital signs. But so when we are going over the vital signs, remember what all of them are. And I say that in tongue-in-cheek a little bit, but we're serious. We have to see all five vital signs. So we're going to go over heart rate, blood pressure, temperature, oxygen saturation, and then the fifth vital sign. And I know what you're saying that's probably pain, because we were told that, but it's not. It's not the fifth vital sign. And the fifth vital sign is the one that we find missing most of the time. And that's respiratory rate. And respiratory rate cannot be replaced with an oxygen saturation value. So all of this will be discussing individually again. And the first vital sign we're going to start with today, and that is with heart rate. But before we go into details about heart rate, emphasize a few key points. First, we need a full recording of vital signs. And often again, we find that they're incomplete. And we can't see that clinical picture with an incomplete set of vital signs. Second, a single vital sign parameter has really low predictive ability for adverse events. Using combinations will really significantly increase that predictive capabilities and help us tell the story, help you tell the story of what is going on with your patient. Three, the more you understand vital signs, the more uncomfortable you will be with abnormal values, and the more uncomfortable you will be only looking at one vital sign in isolation. And then four, it's not just one vital sign. It's the trends in vital signs that make vital signs so important. Where was the patient? Where is she now? And then anticipate where that value may change in the future based upon the clinical scenario. So with that, those key points kind of define in what we'll be talking about, let's start now with heart rate. You think back on cardiac output formula, heart rate times stroke volume. Heart rate gives us a tremendous amount of clinical information about where the patient's cardiac output is. And remember, cardiac output is survival for the patient as well as the fetus. So cardiac output equals heart rate times stroke volume. This is going to be an essential component of what makes up that survival. We know that a normal heart rate is between the range of 60 and 100 beats per minute. We know that. So let's talk about the abnormals and what may influence the heart rate to become abnormal. We'll start there with bradycardia. The bradycardia is defined as a heart rate of less than 60 beats per minute. Yeah, and this is where I wanted to kind of chime in and comment on bradycardia because I think now that we're all wearing our smart watches and we're seeing what our heart rates are all the time. Many of us, myself included, have a resting heart rate of under 60. But I'm not pregnant. And for a pregnant woman to have a heart rate, a resting heart rate of under 60 is highly unusual. It is theoretically possible that it could be in the normal range, but it's highly unusual. And so you always want to assume it's a potential problem because if a pregnant woman's going to be increasing her cardiac output to meet the needs of the pregnancy, she's going to have to increase her heart rate and her stroke volume both. But it's mostly stroke volume, not heart rate. So we would expect her to have a normal heart rate of above 60 beats per minute, the vast majority of the time. Yeah, it is unusual. I will say that I've reviewed a couple of cases recently where there was persistent bradycardia, which again, we normally don't see that. So really understanding the why is critical to understanding what does this even mean? You know, we don't see it that often. And so instead of normalizing it, we look for those conditions to see what may be causing it. So we broke the causes of bradycardia down into cardiac and noncardiatic. So cardiac, we think of a dysrhythmia, for example, it could be a heart block in our patient population. It could just be basic bradycardia, but what goes with that? So is there any component of heart disease for this patient? Has the patient had a myocardial infarction? Congenital heart defect that has been repaired. So post-surgical congenital heart defect or myocarditis. Those are some of the examples of cardiac causes for bradycardia impregnancy. Noncardiac causes would be things such as obstructive sleep apnea, hyperkalemia, certain medications may lower your heart rate, especially like sedatives or sleeping aids that we sometimes give patients, especially if they're on the antipartum unit. And beta blockers. Yes. And hopefully we would understand that and know that ahead of time. But sometimes, you know, we do, in our history and physical, a patient may leave off some of that information, but beta blockers certainly they do lower your heart rate. Or you could be treating somebody with repeated doses of a beta blocker because of their high blood pressure, and then they develop a bradycardia as a result. Well, it's pretty obvious in that situation what it is. We don't have to do a major cardiac workup to understand why this patient is bradycardic. You got to take all that information into account. That's true. And that's the essential component before you give a dose of libato law, you just check a maternal heart rate and make sure that it's over over 60 beats per minute before you give that next dose or before you even give the initial dose. In fact, some hospitals are real concerned about that because we're giving these boluses of IV libato law for hypertension. And some hospitals are saying, hey, you need to do continuous ECG monitoring. And you really don't. You just need to check a heart rate and make sure it's over 60. Yeah, and some of the driving force behind that is if you may be wondering in your own facility. In the obstetric population, we don't need to do the same kind of monitoring as we do in different populations of patients. But if you remember back to that cardiac output, output formula, cardiac output is controlled by heart rate and stroke volume. So let's take an example of an elderly person with heart failure. They're desperately trying to maintain their cardiac output and they may not be able to maintain stroke volume, but they can keep that heart rate up. And if you just knock out their heart rate and slow it, you may have just compromised their ability to maintain their cardiac output. So that's the rationale for that. But in our patient population, that's really not a thing. So you should be able to give a libato law without continuous monitoring. That's true. And we're not also giving a continuous drip of it. So if you were giving a continuous drip of libato law or any beta blocker, then they're going to need to be on continuous ECG monitoring. Other causes that we broke down outside of the medications for non-cardiac causes, substance use, some substances used by our patients can lower the heart rate certainly and or overdose. Both of those can cause a brate of cardiac. And then don't forget another vital sign and that's your temperature. If I The patient has hypothermia. It's going to slow down her metabolic processes, including her heart rate. That's essential as well. Now that we've covered the Braydecardia, causes and understood the why, let's talk about a condition that is much more common in our patient population and that is TACAcardia, or a heart rate of greater than 100 beats per minute. Understand that a lot of times we see TACAcardia normalized. Any heart rate that is consistently over 100 beats per minute is abnormal and we should not normalize it. We know that heart rate increases 10% in pregnancy, but it should still not be over 100 beats per minute. And again, that is a little component that we often hear and see in clinical practices, "Oh, she's just pregnant." And that is abnormal. There's no such thing as TACAcardia of pregnancy. It's not a thing. TACAcardia is TACAcardia period and you can't just chalk it down to the fact she's pregnant. Yeah. What about the saying of, "Is just sinus TACAcardia?" Do you hear that? We hear that a lot, right? Yeah. First TACAcardia, so first of all, TACAcardia should be your first sign that your patient is trying to compensate for something. There is some pathology going on that is requiring compensation. She has to increase her cardiac output for some reason. Sinus TACAcardia tells you the heart electricity is working the way it's supposed to work. It doesn't tell you that there's no pathology that's leading to the TACAcardia. It just means she's got a P wave that's preceding the QRS wave appropriately, which reflects the normal electrical patterns in the heart. That's all sinus TACAcardia is. The sinus rhythm. But you still have to understand why is she TACAcardic? It's not normal just because it's common. Now it might be resolved easily. It might be because she's pushing. And then it goes back down to normal at rest. So what we're talking about is resting baseline TACAcardia that's not explained by exertions such as pushing a baby out. Right. The same thing is if you're running or going up flights of stairs, your heart rate is going to go up. That is a normal component to increase your cardiac output to the muscles. This is pathologic though when you are TACAcardic at rest. It's consistent. It's not an isolated value as we just said. So understanding the why cardiac causes, it could be arrhythmia and don't just assume again that it is a sinus TACAcardia. We don't know that the rhythm is appropriate unless we monitored it. So just taking a heart rate and it being 120, it could be a value that is also has some other pathology underneath it. Another cause, cardiac cause would be myocarditis or an acute coronary syndrome. So understanding the cardiac, if there's any cardiac potential there is really essential. And I think you'll see here that this list of cardiac specific causes of TACAcardia is relatively short. In pregnancy most of the time when you have TACAcardia, it's not a heart problem. In fact it's the opposite. The heart is doing exactly what it's supposed to do, which is compensating in a normal manner for a problem. And I want to expand on that just a little bit about why that's such a problem. When your heart is beating fast, the faster it goes, the less time there is for filling of blood in those ventricles. So let's think about taking a glass of water and you've got a glass that's empty and you've got the faucet that's running and you want to fill this cup. If I hold the cup under the faucet, the running stream of water for a long period of time, there's plenty of time for it to fill. So I filled the cup, I pour it out and if I, let's say that I'm trying to fill this cup but I've got less and less time under the faucet to fill it, there's going to be less water in the cup. That's just the way it goes and it's the same with the heart, the faster the heart beats, the less time there is for the ventricle to fill with blood. And if you don't have enough blood in the ventricle, you're not going to pump enough blood and therefore your cardiac output is going to go down because your stroke volume has gone down. So tachycardia can help to a certain point, but at some point it's going to hurt because you have less, you don't have adequate time to fill those ventricles. But most of the time tachycardia is not an inherent heart problem. It's a response to a problem outside the heart and it's your job to figure out what that problem is. Right. And again, we see this normalized so much. We have, we even have patients or even nurses or physicians say, you know, I ran a really high heart rate during my pregnancy and I was fine. And it just kind of like makes me shiver all over when somebody says that. Yeah. And I practice in the desert in Arizona and you know, increased heart rates and even to the point of tachycardia are not unusual in patients out here because they're chronically volume depleted. We live in a desert so literally with every breath you exhale, you're losing water. So women have to drink a lot of water to meet the needs of pregnancy. And if they don't, they come into the office and they have a resting baseline tachycardia. 100, 110, sometimes 120. And my staff all have instructions. You're going to give those patients a bottle of water and repeat their pulse and it's amazing how quickly the pulse comes down when you just fill the tank. Yeah. And so that's the understanding the why, which is not cardiac related. It's under the category of non cardiac for understanding the why in that patient. Yeah. And just about two weeks ago, I had a patient in the office where we gave her a bottle of water and her pulse, her resting pulse when she came in was going up to the one thirties to the one forties. Her blood pressure was normal. Her oxygen saturation was normal. Respiratory rate was normal. She was asymptomatic. No chest pain, nothing. And we watched her for about 45 minutes and gave her some water and her heart rate just simply would not come down. So what did I do? I sent her to the hospital for further monitoring and evaluation to figure out what the issues was. So you can't ignore it because the patient feels fine. She ended up doing well. She needed more fluids than what we were able to give her in a short period of time. But these kind of things happen and you can't normalize it because there could be another issue. Right. Exactly. And have that consistent of a problem to makes it even more of an issue not to normalize it. So you couldn't fix it. So you did something else. So other noncardiac causes of tachycardia just think of a general need to increase cardiac output. So if you think about it, heart rate times stroke volume equals cardiac output. If for example, stroke volume falls, heart rate is going to go up. So to compensate to increase your cardiac output. So anytime the body needs to increase cardiac output, the heart rate can rise to compensate. And the last thing you want to do is block that heart rate. We've seen that and we've illustrated that in certain case studies in the past few years that we have done on podcasts that we start treating a symptom like heart rate and not understanding the why you can decrease cardiac output even more and the patient will become even more compensated. This especially occurs in the hemorrhage patient or a patient who is volume depleted. They will have high heart rates and you have to recognize that that is compensation to keep the cardiac output higher. If you've got a patient who's tachycardic post surgery, she's bleeding until proven otherwise period end of sentence. Exactly. And then you look for signs and symptoms of shock because shock, their heart rate is going to go up in most cases. And so you start looking for shock. The other things that you consider as noncardiac causes, hypoxia. So tissue hypoxia. Again, that's usually on going. So it starts and it gets worse and worse and worse and worse and then the patient's heart rate starts going up. And then also metabolic acidosis. One of the first signs of metabolic acidosis is for the patient to raise her heart rate. So consider that as a cause. Pulmonary edema or anything respiratory. Pulmonary edema as well as pulmonary embolus. High heart rate symptom. So what goes with that? We're going to look for respiratory rate. We're going to look at patients blood pressure. We're going to look at causes of pulmonary edema, cardiogen again, noncardogen. Another really important cause of tachycardia is infection. So what would go with that? We would be looking for hyperthermia as another sign and symptom of infection and or sepsis. So, high heart. rate association with tachycardia and infection in sepsis. And then anemia acute versus chronic. And I'm sure Stephanie, you want to say something about that. Yeah, acute anemia is much more likely to result in tachycardia than somebody who's dealing with chronic anemia because the body can compensate over time. But if you have acute anemia, it's usually because you've also lost volume. You've bled because in this situation because you've had a baby most likely. But chronic anemia, the body can compensate for. So it's kind of shocking sometimes you can have patients with pretty significant degrees of anemia. And depending on how long it's taken them to get there and how well they've maintained their volume otherwise, they may be able to compensate and have their heart rate is probably lower than it would be if they did not have anemia. But it may not get up to the tachycardia phase, except very minimal types of activity will make their heart rate go skyrocketing. Okay. So that one patient that I just referenced that had the high heart rate in the office in my mind, I also wanted acute blood work to understand is she anemic and is just any activity moving on and off the bed, walking to from her car. Is that she's got to compensate so much because she just doesn't have enough oxygen carrying capacity because her blood count is low. So that's an example there. Yeah. And I think of another example that would be more acute. And that, let's say you're working in triage and you have a patient that comes in with a high heart rate. And she is, doesn't have any obvious sign and symptom of hemorrhage, but you start taking a history, doing a physical exam. And now you're considering whether this patient has had an abruption or not. So that would be an example of that acute clinical picture that may lead to tachycardia in the mom, but you may not see very many signs or symptoms in the fetus yet or in the uterine activity. Yeah. One of the most memorable abruptions that I was part of, a part of managing was a patient who came in with just not feeling right and decreased fetal movement, no vaginal bleeding, no abdominal pain. And the first set of otel signs, she was significantly tachycardic and hypotension, but the tachycardia was the casual comment that got dropped before I was even called to see the patient. Somebody goes, oh, I'm going to go see this patient in triages. She's, you know, decreased fetal movement in the heart rate is 140. And I'm like, I'm coming with you. And of course, she had a huge concealed abruption. Right. And so, yeah, what goes with it, again, that understanding the why and what goes with it, it's just not an isolated thing. You're considering the why, then that may be a possibility. Certain medications that we give, obviously, we give some of those that will increase the heart rate. We know that that's pretty easy, but that's the reason why, again, we know that their heart rate may go up. And example, um, breathy to beodeling, you, you take a maternal heart rate before you give another dose. And if the heart rate's over 120, then we would withhold that dose and maybe either not give it or consider another medication, depending on why you're giving it. And then lastly, uh, substance use or withdrawal, these patients can have a high heart rate, as well, depending upon the substance. So again, knowing the why, not just having a heart rate, but understanding the why and what are the possibilities or what goes with it, what, what clinical picture goes with it, what other assessment parameters go with it. So, I kind of, you know, as we're wrapping up talking about heart rate, I wanted to just make a comment about the, the role of an ECG or continuous ECG monitoring. So the role of an ECG is to evaluate the rhythm and to determine if there's any underlying pathology such as a myocardial infarction. So if you have a patient that you suspect of having a dysrhythmia or who you suspect of having a myocardial infarction, then you absolutely need to do an ECG. But a 12 lead ECG to confirm that it's sinus-tackicardia is not necessary. You can feel that patient's pulse and know if it's regular or not. If you've got a regular rate and rhythm or regular rhythm in this situation, then the likelihood that you're going to find some underlying dysrhythmia is quite low, especially if there's no other history to make you think that there might be something there or she's not having chest pain or whatever that might make you think she's having a myocardial infarction. So just be clear of what it tells you. It's going to tell you about whether or not you have normal electrical conduction in the heart. Do you have a dysrhythmia and do you have a myocardial infarction? That's what you're looking for with an ECG. And the same thing goes for continuous ECG monitoring. The only people that need continuous ECG monitoring are those that need to be monitored because they have a dysrhythmia or you're worried they might develop a dysrhythmia or they've got some underlying cardiac pathology that is at risk or you're using high risk medications that require continuous monitoring, continuous beta blocker infusions, etc. So there are certainly roles for these, but what we don't want you to think is that a normal ECG is an excuse for not having to look for any other underlying issue because the vast majority of your patients with tachycardia and bradycardia for that matter are going to have a sinus rhythm. And the ECG is going to be unremarkable except for the rate. Right. It's not our bread and butter like it isn't in a six-year-old man that comes into the emergency room with chest pain is certainly different clinical circumstances usually than a 23-year-old pregnant patient coming in with tachycardia and possibly chest pain. And then to close us out you'll notice that we talked very little about pain and anxiety in the role of abnormal heart rates. And that's because we want this to be a last-case scenario. This should not be the first thing that you think of. This should be the last thing that you think of. You should assume that there is a problem, not assume that it's because she's in pain or anxiety. Remember we're talking about resting abnormal heart rates. And no, the likelihood that your pregnant patient has developed a new onset, severe anxiety disorder, enough to create resting tachycardia from labor and postpartum and has not had this issue prior to that presentation. I mean you've won the lottery if that happens. It's extremely unlikely. Yes, she's probably anxious, but she's probably anxious because there's some underlying pathology. And it's the result of the pathology, not the cause of the tachycardia for example. So true. And we, I know again, y'all hear us talk about that a lot. And it is a trigger for us because we have seen so much maternal decomposition with those two reasons and the rationales. Or they may wait till they prove everything before treatment starts in some of these conditions, which it really shouldn't. So again, this is focused on understanding the why, understanding the abnormals, understanding why heart rate is so important of a vital sign and not the treatment. That's a completely different podcast and lecture. But we hope this has been helpful for you. And we will continue to talk about heart rate throughout our podcast and the importance of it. So thanks for listening. Don't forget to subscribe and leave us a review. You can learn more about our company at www.clinicalconceptsnob.com. And this is also the website where you would go to sign up for our critical care academy that we just launched. So take advantage of that. You can also follow us on our Facebook page, clinical concepts and obstetrics on X at OB critical care and on Instagram at critical care OB. Also, please email us and send us a direct message for suggestions on future podcasts. You can reach out on any of our social media pages for that as well. So thanks for listening and understanding the why behind TACCA Cardiac and Bray to Cardiac. This podcast was produced by Austin Baird. Are you looking to create a podcast? Please email me at podcast-nashville@gmail. That is [email protected]