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Blood Urea Nitrogen (BUN) (Nursing)

by Rhonda Lawes

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    00:01 So let's review those test that we'll look at in assessing real disease.

    00:05 That's why we're in this video series so you can get a feel for what you can look at and what you'll be evaluating is part of the healthcare team First is the BUN.

    00:15 That's Blood Urea Nitrogen.

    00:18 We don't often call it the bun, we usually say BUN.

    00:21 Now serum creatinine is another lab test will look at.

    00:25 So so far we've looked at two lab tests.

    00:28 BUN and Serum Creatinine.

    00:31 They'll also look at estimating the GFR from the serum creatinine.

    00:36 Now that's the glomerular filtration rate.

    00:39 It's a really good indication of kidney function.

    00:41 And lastly a urinalysis.

    00:44 When we say including sediment that is like the whole (shebang).

    00:49 We're looking at it visually we're looking at under a microscope.

    00:52 We're doing all kinds of tests on this urine to see how the kidneys are functioning.

    00:57 So these are four major test that healthcare provider will usually order and the whole team will be evaluating.

    01:04 BUN, serum creatinine, estimating the GFR from the serum creatinine and urinalysis.

    01:12 Now, I know I've gone through those a couple times because these are for Cornerstone test that you need to be very familiar with.

    01:20 Now does the BUN, is it came from a blood test, or from a urine test? Right? It's blood, just as the serum creatinine and then the estimation of the GFR is something that we do as a calculation from the serum creatinine, but the urine analysis is actually looking at urine.

    01:40 Let's talk about the BUN, and as urea and renal function.

    01:44 This lets us know how your kidneys are working.

    01:46 So let's back up and talk about urea.

    01:48 Woo, that sounds like fun.

    01:50 So Urea is a water soluble nitrogen containing waste product.

    01:54 Now, normally your kidneys can filter that out from the blood into the urine.

    01:59 So urea is a water-soluble waste product.

    02:03 That's the most important point I want you to remember.

    02:06 So when we talk about BUN, we're talking about a waste product that is water soluble.

    02:12 Now, it's a sign of the kidneys are compromised if you see an increased BUN level.

    02:18 Can also be a sign that the patient is dehydrated, but we'll be watching a BUN closely if it's going up and it's elevated.

    02:25 Now, we measure this by doing a blood test, BUN, a blood urea nitrogen test.

    02:32 Now, these are the normal levels.

    02:34 I know, I know there is a lot to memorize the good news is when you're actually actually practicing these values will be printed right alongside what your patients values are because every lab is a little different but we want to give you a normal range reading kind of keep in mind.

    02:50 So the only way to remember normal values is just keep looking at them over and over and over again.

    02:57 Be sure to quiz yourself on this, because these are important parts of exam questions and your professional practice.

    03:05 Okay, so what really does the BUN do, what does it tell us? Well, it's an indication of both your renal function and your liver function.

    03:14 Okay.

    03:15 Hello.

    03:15 Did you catch it? That's pretty cool 1 Test, 2 organ systems that lets us know what's going on as far as the amount of urea nitrogen in a patient's blood sample.

    03:27 So again, where does this come from? Well the liver and the kidneys are involved.

    03:33 In the liver, makes urea from another waste product.

    03:37 Okay. So step one.

    03:39 We know that a BUN is the measure of urea in your blood and so it's the blood urea nitrogen content. Right? So we've got that as a lab test.

    03:48 We know that urea comes from the liver making it from another waste product.

    03:54 Now in case that's confusing stay with me.

    03:57 Urea comes from ammonia.

    04:00 Now, ammonia is a waste product after the liver breaks down protein.

    04:05 So this should kind of start making sense. Right? If you've taken care of a liver failure patient.

    04:10 We don't like to give them a lot of protein because they end up turning it into ammonia enough that liver is limping.

    04:17 Then the liver can't break it down and turn it into something water-soluble.

    04:22 That's a problem.

    04:24 So urea normally happens in my body when the liver turns ammonia into urea.

    04:31 Okay, so let's walk through how that happens.

    04:33 We know that we get ammonia as waste product after the liver breaks down protein in a process called deamination.

    04:41 Now, you see look at the molecule we have there for you.

    04:43 You've got ammonia, which is NH3, Scott nitrogen and three hydrogen.

    04:49 Don't worry, you won't ever have to draw that as a nurse, but we want you to understand how this process works in your body.

    04:56 So I eat a steak.

    04:58 It's breaking up some protein in my body, end up with ammonia as a waste product from that, what happens next? Well ammonia needs to be converted to urea in order to be excreted into urine.

    05:12 So the livers got to turn the ammonia into urea which is water soluble so I can pee it out of my body.

    05:20 So it's really important that the liver be able to convert the ammonia to urea in order for me to be able to get rid of it via my pee.

    05:29 If I can't, I'm going to have elevated ammonia levels, Now this is really traumatic, If you've ever seen a patient who has a high ammonia level.

    05:39 People with liver failure tend to have high ammonia levels because they can't turn the ammonia into urea because our liver is not functioning well.

    05:49 Excess ammonia is neuro toxic.

    05:52 Toxic is never a good word. Right? Neuro means it's toxic to my brain.

    05:58 So impaired livers lead to elevated ammonia levels and that is neurotoxicity.

    06:04 This can be life threatening.

    06:05 You'll see confusion as the most levels get higher and higher even to the point where the neuro changes are so difficult it can lead to coma.

    06:14 So if the body can't convert ammonia to urea the body can't get rid of it excess levels of ammonia lead to neurotoxicity coma and death.


    About the Lecture

    The lecture Blood Urea Nitrogen (BUN) (Nursing) by Rhonda Lawes is from the course Introduction to Assessment of Renal Function (Nursing).


    Included Quiz Questions

    1. 7–20 mg/dL (2.5–7.1 mmol/L)
    2. 3–10 mg/dL (20–30 mmol/L)
    3. 20–50 mg/dL (40–100 mmol/L)
    4. 50–100 mg/dL (100–150 mmol/L)
    1. How well the kidneys and liver are functioning
    2. How well the adrenal glands and pancreas are functioning
    3. How well the bladder and ureters are functioning
    4. How well the spleen and pancreas are functioning
    1. Liver and kidneys
    2. Pancreas and spleen
    3. Adrenal glands and gallbladder
    4. Pancreas and adrenal glands

    Author of lecture Blood Urea Nitrogen (BUN) (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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