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Causes of High Level of BUN (Nursing)

by Rhonda Lawes

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    00:00 So when you see urine that indicates dehydration, is it going to be lighter or darker? Right, it's going to be so darker so dehydration can also cause an elevated BUN.

    00:13 Okay that tracks with what we've what we studied, right? An elevated BUN could come from, we've got problems with organs, we've got excess protein or if we've got some challenges with dehydration.

    00:26 So someone who is dehydrated is going to have an elevated BUN.

    00:31 Here's why you care, first of all, helps you keep your patients safe.

    00:35 Second of all, classic test question, they're gonna ask you to know if you can assess your patients and the effectiveness of their treatment in rehydrating your patient.

    00:48 So you're gonna want to know what a normal BUN is because if your patient's treatment is effective, Someone who was dehydrated, you should see their BUN come back within normal range.

    00:58 That's why a patient's history is so important.

    01:01 We've got the picture of the nurse up there to remind you that's you so you're always gonna want review the patient's history for renal disease or other possible causes of the BUN.

    01:13 The test is worthless without you so your job is to be a detective and figure out what most likely contributed to that abnormal BUN level for your particular patient.

    01:24 Okay, so let's have some fun.

    01:27 Remember, we're talking about what do you do when your patient has a high BUN? So this is something you need to have in your toolkit, does one high BUN have to mean AKI? Well the answer is no but I want you to understand why.

    01:43 BUN in is not the best diagnosis of acute kidney injury because it's dependent on other factors that don't involve the kidneys, right, so it's independent of kidney function.

    01:53 So it doesn't mean we wouldn't it look at it or consider it and I'll tell you how to do that later but know now in any lab value, it's trends plus patient assessment that helps you keep your patient safe.

    02:06 So one value does not a diagnosis make.

    02:10 I'm gonna say that again because I say it to my students all the time.

    02:15 One value does not a diagnosis make.

    02:18 You want to look at trends and you want to look at patient's other assessment information to bring that all together, and that what we're learning here.

    02:26 What do you do when your patient's lab value is abnormal? Remember, BUN has factors outside of the kidneys that can cause an abnormal value.

    02:36 So what's your job? it's obvious - consider other causes of high BUN.

    02:43 SO it may or may not be acute kidney injury but first let's consider some other areas.

    02:49 Remember urea levels increase with age - the older I get, the higher my urea levels become.

    02:56 Also if I'm somebody who's having an extreme amount of protein in my diet, maybe I'm a bodybuilder or a carnivore eater, that may also impact my urea level because that's a byproduct of protein metabolism.

    03:09 So if I'm looking at this patient, they have a high BUN, I don't have to necessarily assume it's as acute kidney injury, but then you'll be thinking, "hey how are they doing on their fluid-volume status?" Are they severely dehydrated? What signs would I look for? Well somebody who's severely dehydrated is going to have a blood pressure that's lower than normal and a heart rate that's higher than normal.

    03:32 Now is that is a classic test question.

    03:34 If somebody is hypovolemic or dehydrated, you would expect their blood pressure to be low, usually less than 100 (mmHg) and their heart rate high, above 100 (bpm) because the body is frantic, it's trying to compensate.

    03:48 If you don't have enough volume in your intravascular space, it's gonna try moving around a lot faster and that's why your heart rate is so high.

    03:56 So we may have a high BUN because of severe dehydration.

    03:59 Check, assess your patient to see if that's the problem.

    04:03 You might have a urinary tract obstruction.

    04:06 This one is not as hard to assess because a urinary tract obstruction is generally a kidney stone.

    04:12 Okay, that means you got something blocking that exit system from the patient's body.

    04:17 Right, you eat protein, your liver chews it up, you end up with ammonia, your liver makes out ammonia into urea, sends it down to the kidneys. the kidneys filter that from the blood, try to get it to leave the body, but if your urinary tract has a big old stone in it, that's all gonna build up in the body because it can't leave the body.

    04:37 And if you've ever seen somebody with a kidney stone, there will be no doubt that their urinary tract is obstructed.

    04:44 Make sure you have that underlined as "obstruction" and not as "infection".

    04:50 Now the next two reasons have to deal with your heart.

    04:52 Congestive heart failure or recent heart attack means your heart's not gonna be pumping as efficiently as we need it to and that may lead to an elevated BUN.

    05:03 Another final one might seem kind of odd to you but it actually ties back up to our first reason.

    05:09 In burns, your skin is damaged and part of what our skin is, remember it's the largest organ in our body, it's supposed to keep all that wet stuff on the inside of our body.

    05:21 When that skin is damaged, you have massive fluid-volume shifting in a patient's body so just about as fast as we can put fluids into a burn patient, it sometimes gets dumped out into the tissue because of the damage to the capillaries So even though that patient technically has a ton of volume on board, it's not in the intravascular space.

    05:44 It just doesn't stay there very well and you have fluid shifting out into their tissues so it can act just like severe dehydration because they are intravascularly dehydrated.

    05:55 So I'm a nurse, I get a high BUN back, I'm thinking, "hey it could be acute kidney injury" we'll talk about that but also is my patient dehydrated? do they have a kidney stone? is their heart functioning well? what's their blood pressure and have they had a recent burn, significant burn?


    About the Lecture

    The lecture Causes of High Level of BUN (Nursing) by Rhonda Lawes is from the course Blood Urea Nitrogen (BUN) – Renal Assessment (Nursing).


    Included Quiz Questions

    1. Dehydration
    2. Urinary tract obstruction
    3. High protein diet
    4. Malnutrition
    5. Liver disease
    1. A heart rate of 148 beats/min and blood pressure of 79/54 mm Hg
    2. A heart rate of 54 beats/min and blood pressure of 188/81 mm Hg
    3. The temperature of 38.9 ℃ (102 ℉) and respiratory rate of 32 breaths/min
    4. The temperature of 39.4 ℃ (103 ℉) and blood pressure of 130/85 mm Hg
    1. Fluid volume shifting
    2. Fluid volume excess
    3. Acute Liver injury
    4. Inflammation

    Author of lecture Causes of High Level of BUN (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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