00:00
Now just like the
name says the BUN
to creatinine ratio
is an actual formula.
00:06
BUN the blood urea
nitrogen goes on the top
serum creatinine
goes on the bottom.
00:12
Now, I'm going to tell you what
happened to my Aunt Crystal.
00:15
She was in the ICU
at the very same time
I was creating this
presentation for you
and my cousin was
texting me lab values
and my eyes were
as big as saucers.
00:25
Luckily. She's doing great.
00:27
She's back home,
but for a while there it was
not looking positive for her.
00:33
Okay, so let's do the math.
00:34
73/4.010 mg/dL What do we get?
This was going to be outrageous
because my aunt was so sick.
00:44
Wait a minute the numbers 18.20
well what's considered normal.
00:51
12 to 20.
00:53
Well while my aunt had
a lot of things going on
the reason she went
to the hospital
was for severe dehydration.
01:01
So even though these
numbers look abysmal,
It was still was within the normal
range for BUN to creatinine ratio.
01:08
BUN wasn't normal,
serum creatinine wasn't normal,
but she was still within the normal
range for a BUN to creatinine ratio.
01:17
So what does this BUN to
creatinine ratio tell us
that a simple
creatinine or BUN can't.
01:24
Well it can help us determine
if the cause of the elevated BUN
that high urea or
creatinine is a renal
or non-renal cause.
01:33
Now I don't want to
buzz through that
because this is something
we use in practice
and it's something you
need to be aware of.
01:39
The math is simple but understanding
what it represents is really important
because of BUN to
creatinine ratio
can help us recognize if the
problem is renal or non renal.
01:53
In this case,
It wasn't my aunt's kidneys
that were the problem.
01:57
The problem was they
had a pre renal issue.
02:00
Were not getting
enough blood supply.
02:02
She was in acute kidney injury,
they replace the fluids and her
kidneys perked right back up
and she did fine and
was discharged home.
02:11
So why you want to know what
the BUN and creatinine ratio is
is it can help you determine
through very simple math
if the cause is
renal or non-renal.
02:22
Now let me give
you a quick chart.
02:24
You see in the left-hand column
you have greater than 20,
greater than 12 to
20 or less than 12,
so greater than 20 s going
to be a pre rental problem.
02:34
You can see that
she was on her way
if she wouldn't have gotten help,
if she wouldn't have gone to the hospital.
02:39
She definitely would have kept
right on going up past 20.
02:43
So when you get
a value like this
you want to watch for signs of
hypoperfusion of the kidneys,
my aunt was hypo perfused.
02:50
She was so intravascularly
dehydrated
her kidneys were not receiving
an adequate blood supply.
02:56
You'll also want to check for
things like excessive protein
or GI bleeding,
remember those red blood cells
have hemoglobin
which is a protein
that can also cause an
increase in the ratio.
03:07
Now if it's 12 to 20,
that is within the normal range,
but there might be a post renal
problem some type of obstruction.
03:14
Less than 12,
that's not a good sign.
03:18
That's an intrarenal problem.
03:20
Now, it may also
indicate liver disease
or malnutrition there just
may not be hardly any protein
available to the patient
because they're
either malnourished.
03:30
They're not eating or the
liver can't process protein
like we depend on it doing.
03:35
So you want to keep in mind if
you're taking care of a patient
most patients have a
BUN and a creatinine
you can look at that
BUN to creatinine ratio
and line it up with the rest of the
assessment you see with your patient.
03:48
So that was the basics of
the BUN to creatinine ratio,
but I want to point out a couple
of other categories
to keep an eye on.
03:55
If your patient is elderly
they may have an elevated BUN to
creatinine ratio as a baseline,
meaning they have that
before they came into you
because as we age you have
a decreased muscle mass.
04:07
So keep that in mind,
the out early usually
are a special case.
04:11
We're dealing with
medications and lab work
and this one is no exception.
04:15
So you're elderly patients may have
an elevated BUN to creatinine ratio
normally as a baseline.
04:22
So keep an eye on your Trends.
04:24
Now the next one you can
have other reasons for having
a disproportionate rise in
BUN relative to creatinine,
so that's what
we're talking about.
04:33
Why do we have such a higher
BUN than we do the creatinine
what can be caused by
hyper catabolic states,
high-dose glucocorticoids,
and the reabsorption
of large hematomas.
04:45
I want you to kind of think
of that just for a minute,
hyper catabolic states your body
for whatever reason is
under extreme stress
and is just ripping
through your cells.
04:57
High-dose glucocorticoids
mess with everything, right?
Protein, fat,
metabolism, blood sugars,
they can wreak havoc on a body.
05:05
When we say high
dose glucocorticoids,
this isn't what somebody's
taking in an inhaler
for their asthma.
05:13
This is high-dose steroids
probably given orally or IV.
05:19
The last one reabsorption
of large hematomas.
05:22
Remember that's blood cells being
reabsorbed back into the body
and that's going to be a
source of high protein.
05:29
So those our special
notes to consider
when you're evaluating a
patient's BUN to creatinine ratio.
05:35
Watch out for the elderly.
05:37
You can expect a change there.
05:39
Hyper catabolic states,
high-dose glucocorticoids
and the reabsorption of
a really large hematoma.