Introduction to Blood Urea Nitrogen (BUN) Test (Nursing)

00:00 Hi welcome to our video series on interpreting lab values.

00:04 On this one, we're gonna talk about the BUN or blood urea nitrogen.

00:09 That's how it gets its name, B stands for blood, U for urea and N for nitrogen.

00:15 Now for this test, you're going to need a venous blood sample from your patients.

00:19 You'll use a gel-barrier tube and that is usually what is preferred.

00:22 Now a gel-barrier tube can be more than one color.

00:25 It might be a model red or grey, it might be gold or it might be what we call a cherry-red top.

00:31 Now the red top tube or the green top heparin tube is usually also acceptable.

00:35 Okay, so we've got that out of the way.

00:37 We're looking at a BUN test, we know that it involves a venous sample and you want to put it in a very specific tube for collection.

00:46 Now let's talk about normal values.

00:48 I know all nursing students get stressed out when we talk about normal values because every textbook has a different one.

00:57 Well, that's okay, we're just gonna give you a range and know that when you're in real life practice, every lab also has a little bit different range, so find one and stick with it.

01:07 Right, so we're gonna use 7-20 (mg/dL) for this series.

01:10 Remember, normal ranges might vary depending on the reference range used by the lab where the sample was actually drawn.

01:17 But don't let that stress you out, we've given you a really good normal range to remember of 7-20 (mg/dL) Now there's also things that can go along other factors in your patient's care that can impact a normal BUN level.

01:32 That's what we're gonna to talk about in this series.

01:35 Because serum BUN tells me about your liver and your renal function, now that's pretty cool because by measuring the amount of your urea nitrogen in a patient's blood sample, I can learn a lot about what's going on with their liver or their kidneys.

01:51 So how can one lab test tell us about two organs? Well that's the whole reason for doing this series, I want you to understand that.

01:59 Both the liver and the kidneys are involved in the process of breaking down protein.

02:04 Now the liver breaks down the protein but it ends up with this waste product that the body can't get rid of.

02:10 So that's the process, that's what the BUN test will tell us about.

02:14 So I want you to write this in your notes.

02:18 You see that both are involved and by the liver, we've got it breaks down protein to ammonia.

02:23 So underline that word "ammonia".

02:26 Also, that's what creates the waste products.

02:30 So you're hanging with us, we know this BUN test tells me about your liver and your kidneys.

02:36 We end up with this ammonia byproduct when the liver breaks down protein.

02:42 That's how one lab test can tell us about two organs.

02:46 So we've got these lab tests, it's gonna tell us what BUN nitrogen is.

02:50 We know the normal values are 7-20 (mg/dL) and we know that they might vary depending on the lab.

02:56 So what can we learn when the BUN ranges abnormal? well your biggest concern in clinical settings is going to be when it's too high.

03:04 Now I can't tell you anything by just seeing a high BUN, it's just one very small piece of a big puzzle that is your patient.

03:13 So we're gonna have to look at different things.

03:15 We can look at it might be liver problems, kidney function.

03:18 There might be upper GI bleed - what? upper GI bleeding, what the heck does that have to do with this? Well remember I said the liver breaks down protein.

03:29 In upper GI bleeding, blood is protein.

03:33 Now all of a sudden, your body's got far more protein to deal with, so my kidney might not be functioning, my liver might be not functioning or they may both be fine and I've just got lots of extra protein.

03:46 That may come from upper GI bleeding, maybe my diet or really super high protein intake or I am significantly dehydrated.

03:56 Now look at all those reasons.

03:58 I don't want you to just think about a list, we need to do something to help it stick in your brain so we know it can be organ dysfunction or it can be a really large amount of protein or dehydration, organ dysfunction, extra protein or dehydration.

04:15 Those are the key point that you want to be thinking through when your patient has an abnormal BUN.