Review of the Kidney Functions and Diuretics (Nursing)

by Rhonda Lawes

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    00:00 Hi. Welcome to our video on Diuretics. We're going to give you an introduction to the kidney to help you understand how diuretics work. Okay, so first of all, what do diuretics do? Well, they increase the kidney's output of urine. Our goal is usually to lower blood pressure because less volume means lower blood pressure or decreased edema. So we use diuretics for patients whose blood pressure we want to lower and someone we want to reduce edema. So here's a question for you. What are 3 main functions of the kidney? No peeking, see if you can come up with your 3 main functions of the kidney. Okay, let's see how you did. First of all, cleaning and maintaining extracellular fluid is the first function of the kidney we're going to discuss. Next, acid-base balance. Your kidney play a really important role in maintaining the acid-base balance of your body. Third, the kidneys excrete wastes and substances like drugs and other things your body needs to get rid of in order to stay safe. So the 3 main functions of the kidney: Cleaning and maintaining extracellular fluid, maintaining acid-base balance and excreting wastes and substances like drugs, etc. So here's our next question. What's the functional unit of the kidney called and how many are there? So pause for just a minute and put out your best guess. Okay. The nephron is the functional unit of the kidney. It's kind of a funny name but it's an amazing little feature.

    01:36 Each kidney has 1 million nephrons. So if you do the math in your head that's 2 million nephrons per person. Now these guys are incredible. They stretch from the cortex to the medulla of the kidney. So they're all throughout your kidney. Now, the nephron has 3 main parts and I want to break those down a little bit. We've talked about the tubules and you can see those in the drawing.

    01:59 The next part is the glumerulus and the Bowman's capsule. Now I want to talk about how these fit together. See the glumerulus has it's tangle of capillaries. Look at the picture there so you get a good feel for that. It's this tangle of capillaries and when blood flows into the glumerulus, the blood pressure forces water and solutes out of the capillaries and into the lumen of the Bowman's capsule. So take a look at the picture. You see that tangle of capillaries, that's what the blood goes through and then it pushes out water and solutes into Bowman's capsule and that starts its way to the process of the nephron because the water, salt, amino acids, and wastes that make it into the capsule are collectively called the filtrate. So when you're reading and studying when you see that, that's what they're talking about. Filtrate is filtered from the blood and into the tubules and that's why we call this stage filtration. Alright, that may be a little more than you wanted to know about the nephron but you cannot believe how incredible these little units are. So let's go through it one more time. There's a million nephrons in every kidney.

    03:04 The nephrons stretch from the cortex to the medulla and the nephrons have 3 parts: The tubules, the glomerulus, and the Bowman's capsule. Now before we go on, I want to make sure you have that pretty straight in your mind. So pause for just a minute and ask yourself a question. What's the difference between the glomerulus and the Bowman's capsule? Which one of them contains a tangle of capillaries? Alright, hopefully you got that one right that the glomerulus is the tangle of capillaries and it's surrounded by Bowman's capsule. Remember when the blood goes through that glomerulus it pushes out those solutes and the water and it heads on through the rest of the nephron. Okay, now look at this graphic. We're going to layer on the important pieces as we go through but just think of this as we took a nephron and kind of stretch it out to make it easier for you to understand. We start at the glomerulus and you can follow it around all the way down from the cortex, the medulla, the Loop of Henle and then back all the way around to urine excretion.

    04:09 So follow that in your handout so you kind of know the route of what we'll be talking about.

    04:13 Now let's lay on those sites that we just talked about. We've got the PCT, the DCT, the TAL, the collecting duct and that's where urine is excreted. That's the first layer. Now let's take a look at what goes on at these different sites. This to me is phenomenal, that scientists were able to understand exactly where this happens. So right up there you see sodium 65-70%. We're going to send back to the body about 65-70% of the sodium right at that site. Next, we can see the spots here. We have about 25% of the sodium, potassium and chloride goes back to the body there. The next site about 5% of sodium and chloride goes back to the body there and here at the very last stop on the train 1-5% of sodium, potassium goes back to the body there. Now why do you care about this? Because by designing drugs that work at different spots, these sites of action it determines how much of a diuretic response your patient is going to have. Alright, so the closer you are to the glomerulus, the bigger the impact of the diuretic. So the closer to the glomerulus you are, the bigger the diuretic action. Now, carbonic anhydrase inhibitors, those are CAIs. I say that because it's a mouthful. We lose about 65-70% of the sodium there. Next up, you've probably heard of this group, the loop diuretics. Now this is a pretty potent diuretic that we use for patients with renal failure or congestive heart failure. Next up are the thiazide diuretics. Now look at the difference. You've got the loop diuretics at that 25% of it getting dumped of. Thiazides are 5 times less, only about 5% there. So in remembering which one is a stronger or more potent diuretic, loop diuretics are going to cause more diuresis than a thiazide. Last group are the potassium-sparing diuretics. Now these are the little fellas, right? They're kind of kind and gentle but they are at the stop 1-5%. So this is going to cause the least amount of diuresis. So if I was going to compare the significance of the fact, the strength of the fact of the diuretic, loop diuretics will be the strongest, thiazide is the next strongest, potassium-sparing have the most modest or least amount of diuresis. That's why it matters that you keep in mind where this act.

    06:43 They're not specifically down to the pathophysilogical level but that helps you understand why we use loop diuretics for people who are really in trouble, whose kidneys aren't functioning or in severe failure over something like a potassium-sparing diuretic.

    About the Lecture

    The lecture Review of the Kidney Functions and Diuretics (Nursing) by Rhonda Lawes is from the course Medications for Fluid and Electrolyte Imbalances (Nursing). It contains the following chapters:

    • What Do Diuretics Do?
    • Main Functions of the Kidney
    • The Nephron
    • Diuretic Sites of Action in the Nephron

    Included Quiz Questions

    1. Cleaning and maintaining extracellular fluid
    2. Maintaining weight loss
    3. Maintaining acid-base balance
    4. Excreting wastes and substances
    5. Preventing urinary tract infections
    1. Nephron
    2. Tubule
    3. Glomerulus
    4. Bowman’s capsule
    1. Glomerulus
    2. Loop of Henle
    3. Collecting duct
    4. Bladder

    Author of lecture Review of the Kidney Functions and Diuretics (Nursing)

     Rhonda Lawes

    Rhonda Lawes

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