00:01
So once we have that patient
sitting in front of us,
what are some important things
that we can do to arrive
at the correct diagnosis
so that we can fix the
underlying problem.
00:11
The first thing is we
definitely want to take
a good clinical history.
00:13
We want to help to determine
where that source of
potassium loss is coming from.
00:18
Do they have either
transcellular shift.
00:20
Do they have GI losses,
or do they have renal losses?
We want to look at that urinary
potassium determination.
00:27
So distinct that is very
helpful to distinguish
between urinary losses
from shift or GI losses.
00:34
So I can look at something
called the urinary potassium
to creatinine ratio.
00:38
So again that's going to
assume a 24-hour value
of urinary potassium
based on a spot sample
because most patients generate
about a gram of creatinine.
00:46
If I take an aliquot
of 10 mils of urine
and I take that
and measure the potassium value
as well as the creatinine value
that's going to give
me a good idea of
what that patient is losing
within a 24-hour period of time.
00:58
Now a ratio of less than
15 Milli equivalents
per gram of creatinine
is going to suggest
that that kidney is working
and it has appropriate
conservation of potassium
and that the loss of potassium
that they're incurring
is extra renal.
01:13
It's either from GI or
transcellular shift.
01:16
If my patient has greater
than 15 Milli equivalents
per gram of creatinine,
then that suggests that
urinary losses are occurring.
01:25
Now I also want to determine the
acid-based status of my patient
because that will also
help me diagnostically
in terms of what's going on.
01:32
If they have for example
a metabolic acidosis.
01:36
And they have a low urinary
potassium to creatinine ratio.
01:40
Then this could be due to
things like stool losses.
01:43
It could be
if they have a high urinary
potassium to creatinine ratio
meaning that it's greater than
15 Milli equivalents per gram.
01:49
Then I know they have renal
losses and if I'm thinking
about renal and association
with a metabolic acidosis,
it's either going to an RTA
or it's going to be a
non reabsorbable anion.
02:00
Now if I have a patient
who has metabolic alkalosis
and they have a low urinary
potassium to creatinine ratio,
then I think about vomiting
that's not sustained over time.
02:10
But if they have a high unary
potassium to creatinine ratio,
meaning that they
have renal losses.
02:15
Then the next thing
I want to do is
I want to check their blood
pressure and their volume status.
02:20
If they have a
lowish blood pressure
or they appear that
their volume depleted.
02:24
I'm automatically thinking
that this patient may
he be using diuretics.
02:27
They might have a salt wasting of
frothy like Barrter's or Gitelman's
or they had can have
ongoing vomiting
with a sustained
metabolic alkalosis
in urinary losses from that.
02:37
If my patient has a
high blood pressure
or their volume overloaded,
then I think about states like
mineralocorticoid
excess or Littles
the other thing
that you want to do
when you're determining where
this potassium loss is coming from
as you always always want
to check your magnesium.
02:52
Remember you cannot
correct hypokalemia,
unless magnesium is corrected.
02:57
So in terms of treatment,
it's very important to decipher
what the underlying disorder is
so that we can correct that.
03:03
When the potassium
is extremely low
less than 2.5 milli
equivalents per liter,
It's going carry a risk of
dangerous cardiac arrhythmias
and that needs to be
replaced urgently.
03:12
There's a couple of different
ways that we can replace
so if somebody has
mild hypokalemia,
we can give them
oral replacement.
03:20
But if somebody has
severe hypokalemia,
or they can't take oral intake
then we can do parenteral
replacement or IV replacement.
03:28
So the maximum potassium
chloride concentration that we
can actually deliver as about
20 milliequivalents per 100ml.
03:34
So do keep that in mind,
and we want to administer
at a maximum rate of 10
Milli equivalents per hour.
03:40
So when a patient is
extraordinarily hypokalemic,
then we can only deliver so
much parenteral potassium.