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?