Lab Values, part 15: Red Blood Cells (RBCs)

Hi, I'm Meris, and in this video, I'm going to be talking to you about the lab value red blood cells, RBCs. Let's go ahead and get started. So first up, what is the function of red blood cells? It's really straightforward, but incredibly important, which is that red blood cells are responsible for transporting oxygen to the body's tissues and then transporting carbon dioxide back to the lungs to be exhaled. Very important. I cannot function, I cannot be a person if I do not have that exchange of gases. And so that's why we care about the red blood cells.

So what is the expected range? Well, this one, again, has to do with the sex you were assigned at birth, and this has to do with the physical composition of our bodies and the need for oxygen being transported to different types of tissue and the oxygen demands associated with that tissue that differ based on biological sex. So for women, people assigned female at birth, the range here is going to be 4.2 to 5.4 million per microliter. In most of our other lab values, we have been talking about very small amounts and very big volumes. Here we have quite the opposite. A very big amount and a very tiny amount of volume, right? We're talking about millions of cells in microliters of blood. So this is going to be jam-packed, right? That's an important thing to remember when you are thinking about this lab. Now for men, it's going to be 4.7 to 6.1 million per microliter. Again, we are talking about the need for oxygen transport, so I need a lot of red blood cells to get that oxygen where it needs to go and get that carbon dioxide the heck out of here, right?

So what if I have a low red blood cell count? What does that mean? Well, there's multiple different causes that could be going on with this. A big one here is going to be anemia. I can definitely have a shortage of red blood cells if I am anemic, especially if this is blood loss anemia, but just remember, anemia in general can go along with those lower levels. Hemorrhage. Hemorrhage is what I think of as an ER nurse. ER trauma is, I think if you've got low red blood cells, you're bleeding somewhere. And that's not always the case, but it certainly can be one of those causes. Kidney disease is also a potential cause for a low level, and I want you to stop for a second and really think about this. The reason this is is because the kidneys are responsible for the production of a hormone called EPO, erythropoietin, and erythropoietin is used to tell my bone marrow, "Hey, I need you to make some more red blood cells." And this happens because the kidneys start to be hypoperfused because there's not enough coming to them. They start to sense like, "Hey, something's going on. Make some more red blood cells." They tell the bone marrow, bone marrow makes more red blood cells, everybody's happy. But if I have kidney disease, I'm not going to be able to synthesize, to create that EPO in response to low blood volume. So now I need to be concerned about a patient with kidney disease. They may even take exogenous, meaning coming from outside the body, EPO to stimulate their bone marrow because their kidneys aren't going to be doing it for them.

Now, what are some possible causes of elevated red blood cells? Well, the big one here is going to be polycythemia. This is a condition that tells you what it is if you know the breakdown. Poly means many. Cyt means cell. Emia means blood. So this means many cells in the blood. So if I have polycythemia, then yeah, I'm going to have an elevated red blood cell count because I have too much red blood cells. I have too many cells, right? So that's the condition called polycythemia. Polycythemia can be associated with a disease or disorder or an abnormality in the standard function, however, polycythemia can also be as a result of existing at elevation. Let me explain a little further to you what this means. Right now, I'm essentially at sea level, and so my body is interacting with the atmosphere with a lot of pressure. There's a lot of pressure pushing down because I'm lower to the ground. I'm close to the ocean. So there's more oxygen there because the pressure is keeping that oxygen more densely packed. It's just the physics of it.

If you took me to Denver, Colorado for a single day, you're going to see that I'm going to have a little difficulty breathing. I very recently did go visit my cousin in Denver, Colorado, and when I got off the plane, about an hour and a half later, I was like, "Man, I'm really having a hard time. Why can I not catch my breath?" It took me a minute to remember, "Oh, yeah. It's because you're at elevation and you haven't adapted yet." It takes time for my kidneys to get that memo and say, "Hey, hey. We are not getting enough oxygen. I need some more oxygen. Can we get some, please?" And then produce EPO for my bone marrow to respond, for the cells to be created, etc. But after living somewhere like Denver, Colorado for several months, my body will adapt, meaning that it's going to say, "Hey, we are chronically hypoxic because we're at elevation where there's not a lot of pressure and the oxygen is less because it's dissipating into the atmosphere. Because of that, I need to be able to carry more oxygen around, so I'm going to create more red blood cells."

When you then take a person who lives at elevation and they go down somewhere else, it's going to look like they have crazy amounts of red blood cells, right? It's going to be like, "Oh my gosh. Something's not right," but this is a normal adaptation to living at elevation. So that's just a thing to keep in mind. Was this person recently on vacation? Did they spend a couple of months somewhere at elevation? Are they visiting here from somewhere? We need to know that information so that we can be prepared to interpret those lab results. And then also, severe dehydration is something that can cause me to have elevated red blood cells. This is not because I suddenly have more red blood cells than usual. This is because I have less fluid in the sample. This is a dehydration issue that makes it look like a more concentrated sample. So it appears that the cells are more densely packed, but I may still have the same total number of cells in my body, but without the proper amount of plasma diluting things, then it's not going to be in the right ratio.

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 using our quiz questions.

How should the nurse explain the function of red blood cells to a patient?

Red blood cells are responsible for transporting oxygen and carbon dioxide.

The nurse educates a patient who is planning to move to Denver, Colorado, that the one-mile elevation above sea level will affect their red blood cell count in which way?

It will cause it to rise over time.

All right, that is it for this video. I really hope you learned something new. All right. Thanks so much, and happy studying.