Lab Values, part 14: Human B-type Natriuretic Peptides (hBNP)

Hi, I'm Meris, and in this video, I'm going to be talking to you about the lab value human B-type natriuretic peptide or HBNP. Let's go ahead and get started. All right. So first up, let's just talk about what BNP is, and you're going to hear me call it BNP. This can be called HBNP or BNP, but one thing I do want to call your attention to is that if you use that abbreviation, BNP sounds very similar to BMP, which is basic metabolic panel. So if you are using this abbreviation to communicate with a provider, for instance, make sure you are clarifying you mean BNP, like B-type natriuretic peptide, right? Something along those lines. Or BNP, N like Nancy.

So what is BNP? So great question. This is not something that we talk a lot about or that we have sort of out in the community at large, so this may not be a lab value that you're super familiar with. BNP is a hormone that is produced in the ventricles of the heart in response to fluid volume overload. So when you think BNP, you need to think, "Fluid volume overload that is putting stress on my heart," because that is where the stress is going to be, right? If I have more fluid in my body than expected, my heart is going to be working overtime, trying to keep up with the amount of blood that's coming into the ventricles. Trying to get it out as quickly as possible, right, or else we will end up with that traffic jam and that backing up of blood. So this hormone is related to fluid volume overload.

So what is the expected range here? The expected range is that it's going to be less than 100 picograms per milliliter. So again, picograms are tiny, tiny, tiny, and we're talking about a milliliter of blood, so tiny amount in a tiny volume. Essentially, I don't expect that your heart is being too stressed by fluid volume overload in a given day, right? Most of the time, my patients really need more fluid than they have, so typically, my patients are not in a state of fluid volume overload at rest, so I would expect this to be normal. I would expect it to be a low value except if your patient has heart failure. If heart failure is something that they are chronically dealing with, then they will chronically be in some variety of fluid volume overload. That may not mean that they are in a stressed state. It may not mean that they are in a CHF exacerbation. But I just want you to understand that because of the fact-- by the very nature of the fact that they have CHF, they are dealing with fluid volume overload due to the weak or ineffective heart, whatever the cause might be.

So in a patient with chronic heart failure, you need to remember that they may have chronically elevated levels, and for this reason, we need to think about this as something that, just because I see an elevated level doesn't mean, "Oh my gosh. My patient is in a severe fluid volume overload. I need to call the doctor right away." It might mean this patient has CHF and this is kind of their baseline. However, when we talk about an elevated BNP range over that 100 picograms per ml, what I want you to think about here is something is causing fluid volume overload. I don't get worked up about it if it's CHF and this is kind of at their baseline. I expect that, right? And this again is where we go into that NCLEX test-taking environment with that expected versus unexpected findings. I expect that my patient with CHF is going to have a slightly elevated BNP level. I don't expect that my random person out in the community is.

So what are some possible causes of this elevation? Well, obviously, one of the possible causes is heart failure, right? That's just going to be on the menu because heart failure and fluid volume overload go hand in hand. But we can also have acute coronary syndrome where again, we're stressing the heart, and we can have that BNP release because it's coming from the ventricles. And also kidney failure. This one can get forgotten about because we think of BNP as being heart failure, heart failure, heart failure, but it's fluid volume overload. So if my kidneys fail and I am unable to filter and excrete the waste products of my blood, then I'm going to end up with fluid volume overload as well, so you cannot discount that as being a possible cause of an elevated level for your patient.

Now, one of the things that I do want to point out here, though, is that your patients with CHF, this isn't a useless lab value. Yes, it may be chronically elevated, and yes, they may have kind of that baseline level where you say, "Oh, it's coming back abnormal, but it's normal for them. It is within their expected range." However, during periods of CHF exacerbation, these patients will also experience a rise in BNP related to the fact that they are experiencing worsening fluid volume overload. So this is a very important and very useful lab value for us when it comes to the clinical environment, where we can say, "Hey, I have a patient with CHF who is exhibiting some symptoms that make me think they are experiencing an exacerbation. Let's check their BNP level and see how bad it is." The higher the value, the worse the exacerbation is for your patient. So we may also trend this over time, meaning that you come in and your BNP level is 1,500. And oh, yikes. We have a real exacerbation going on, but we're going to keep trending it so that we can see that our efforts are working, that we can see resolution of your exacerbation. So that might be something that you want to explain to your patients who say like, "But I already know that my BNP is high. It's always high. I don't even know why you guys bother checking it," right? That is why.

All right. I'm so glad you stayed until the end because I'm going to test your knowledge of key facts provided in this video with quiz questions.

A patient asks why they're checking his BNP level during a CHF exacerbation since he already knows it'll be elevated. How should the nurse respond?

"We're checking because during times of CHF exacerbation, the higher the BNP, the worse the fluid volume overload."

All right. That is it for this video. I do hope you learned something new. I'll see you in the next one. Thanks so much, and happy studying.