00:00
Hi. Welcome to our video on Loop Diuretics. That's just a fun thing to say. These are the producers
of the greatest diuresis. So these are going to be our go-to drugs. We have somebody who's in
congestive heart failure or renal failure, these are going to be the drugs that we reach for.
00:17
Now all diuretics increase the kidney's output of urine. Our goal is usually to lower blood pressure
or to decrease edema. So that's why we give patients diuretics. We might use it for someone who is a
little bit hypertensive so we try by pulling off some extra volume will lower that blood pressure
or if somebody's edematous, they've got fluid in the wrong space, it's not in their intravascular
space where it needs to be, it's kind of moved out into the tissues we consider that edema and
we'll use diuretics to pull that back in. Okay, let's look at the diuretic sites of action in the
nephron. This is just kind of the overview slide where we took a nephron and we kind of stretched
it out so you can see all the sites of action. The reason this matters is because it helps you
remember why a loop diuretic is stronger than let's say a potassium-sparing diuretic. It's so
amazing that they figured out where each one of these medications work. Look at loop diuretics.
01:12
You'll see in the blue box next to it, it shows you that 25% of the electrolytes leave there. Now
the more electrolytes leave, the more water is going to go with it and that's why a loop diuretic
has a stronger or more potent diuretic response than say a thiazide or a potassium-sparing diuretic.
01:29
Look at thiazides. That's just about 5% of the electrolytes are reabsorbed and down at the
end for the potassium-sparing, it's just 1-5%. So that's why loop diuretics are the medications
that we give to people who really need a diuretic, somebody in congestive heart failure or
renal failure. So, the mechanism of action, that's what MOA means, for loop diuretics we're going to
use an example of furosemide. That's just a very common loop diuretic and that's the generic
name for it. Now the site of action is the Loop of Henle and more specifically the thick ascending
limb of the Loop of Henle. That's not super important. Do you remember it's the thick ascending
limb, that's what TAL stands for but it's right in the Loop of Henle. This is the one that produces
the highest loss of fluid and electrolytes. Loop diuretics are really tough on your potassium
level. It blocks the reabsorption of sodium, chloride and potassium. So if your patient is on a
loop diuretic, you want to be really careful to monitor their sodium, chloride and potassium levels.
02:34
Loop diuretics can be given orally, PO, IM (intramuscular) or IV. Now, we predominantly give it
oral or IV but I want to talk to you about how do we pick which route to give a loop diuretic.
02:48
Well, it depends on how urgent the need is to get that fluid off your patient. Now let's look at
oral first or PO. This can increase the output in about an hour. So if I give a patient a pill of
Lasix or furosemide, which is a loop diuretic, they'll start to see an increase in their output in
about an hour and it will continue for 8 hours. So this is somebody who needs diuresis but it's
not an extreme emergency. Someone who is in significant trouble we're going to use IV. This
will increase urine output as quickly as 5 minutes and it will last for about 2 hours. So just like
other drugs, an oral drug takes longer to kick in but it will last longer. IV starts almost
immediately, I mean 5 minutes is quick, but it will only last for 2 hours. Now, we use this when
we really need to get fluid removed from the patient quickly when they're in trouble, when they're
having breathing problems, when they have pulmonary edema. That's an excess of fluid in their
lungs. Maybe they're in renal failure. We know that they are really starting to build up that
extra fluid. CHF or liver failure are other examples of when we might need to get that fluid off
quickly. Now the cool thing about loop diuretics is they're effective even when the kidneys
don't have really good blood flow. So if we have low renal blood flow, a loop diuretic is still our
best shot. Now GFR stands for glomerular filtration rate. That's just a lab test that we can do
that tells us how well the kidneys are functioning. If they have a low GFR, not a good sign, but
the loop diuretic is still the drug of choice. So you want to watch a patient for signs of
dehydration. Does that make sense? I mean if you have a patient who has extra volume onboard and
we're giving them a diuretic, wouldn't dehydration be a good thing? No. Anything a drug does
well it can do over well and sometimes in an effort to move that fluid off of patient, the drug
takes off too much fluid so you want to watch the patient for signs of dehydration. Now we
have IM up there. That's rarely used. We just put it up there so you knew that we can give it
by that route but you will rarely see it used in the hospital.