Loop Diuretics: MOA and Routes (Nursing)

by Rhonda Lawes

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    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.

    About the Lecture

    The lecture Loop Diuretics: MOA and Routes (Nursing) by Rhonda Lawes is from the course Medications for Fluid and Electrolyte Imbalances (Nursing). It contains the following chapters:

    • Review of Diuretics
    • Loop Diuretics: Mechanism of Action (MOA)
    • Routes of Loop Diuretics

    Included Quiz Questions

    1. Edema related to heart failure
    2. Electrolyte imbalances
    3. Increased creatinine levels
    4. When mild diuresis is needed
    1. Loop diuretics
    2. Thiazides
    3. Potassium-sparing diuretics
    4. Carbonic anhydrase inhibitors
    1. Dehydration
    2. Rash
    3. GI symptoms
    4. Urinary tract infection
    1. Pulmonary edema
    2. Liver failure
    3. Renal failure
    4. Myocardial infarction
    5. Congestive heart failure

    Author of lecture Loop Diuretics: MOA and Routes (Nursing)

     Rhonda Lawes

    Rhonda Lawes

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