Risks of Vasodilators (Nursing)

by Prof. Lawes

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    00:01 Now, all drugs have some risks.

    00:04 There's 3 big ones with vasodilators.

    00:06 So, stop for a minute and make sure we have these 3 clear in your mind just as a list and then we'll break them down.

    00:13 So falls risk is a big one with orthostatic hypotension.

    00:18 Reflex tachycardia.

    00:20 Now, reflex means this is a response, tachy means fast, cardia means heart.

    00:27 So, reflex tachycardia is a really fast heart response.

    00:31 We also, over a long period of time, will have an increase in blood volume.

    00:35 So, for now, let's make sure you have those 3 solid in your mind.

    00:39 What happens to a patient or risk for a patient on vasodilators? They have orthostatic hypotension, puts them at an increased risk for falls.

    00:47 They have reflex tachycardia, and they're going to have an increase in blood volume if they're on a vasodilator for a long period of time.

    00:56 So, why is someone at falls risk when you're on a vasodilator? Well, with that venous dilation, remember a lot of blood stays out in my periphery.

    01:05 So, if I go from a lying to sitting or sitting to standing point too quickly, I'm going to be at a risk for falls.

    01:12 So their blood pressure takes a little while to stabilize.

    01:16 So, particularly patients on vasodilators, you want to teach them, as an educator and as a nurse, you want to teach them that, "Hey, when you're laying down, sit up and kind of get your bearings first.

    01:27 Don't go immediately to standing up because they're going to increase their risk for falling and really hurting themselves." Help them to understand this is normal.

    01:37 For patients that are on vasodilators, most people feel this way.

    01:40 So it's not a big deal if they just take their time.

    01:45 Now, reflex tachycardia. Remember, we're talking about sinus tachycardia means everything's going okay with the electrical conductivity of the heart, right? It's going SA node, AV node, all the way it's supposed to.

    01:55 It's just going too fast.

    01:58 Well, the heart senses, "Wait a minute.

    02:01 Now my blood pressure's dropped.

    02:03 We must have low volume," so it tries to move it around faster.

    02:07 That's what reflex tachycardia means.

    02:09 That's what the strip is showing you there. See how fast those heartbeats are? That's a response to the vasodilators.

    02:16 Now, I don't want to just leave it there. Let's break it down a little bit.

    02:20 Why do vasodilators cause a fast heart rate? Well, it's a baroreceptor response. That's what leads to that elevated heart rate.

    02:27 When we dilate arterioles, those tiny branches of the artery, remember, the arterial blood pressure drops.

    02:34 When we've dilate veins, it indirectly lowers the arterial blood pressure.

    02:39 Long story short, vasodilators drop your blood pressure. Now, this is one of my favorite graphics that they have here. Look at -- this is brilliant. Look what they have.

    02:51 See the red vessels, obviously, those are your arteries, they've got the aortic arch, and then you see those yellow vessels going up.

    02:59 That's talking about the baroreceptor reflex that sends a message to your brain.

    03:04 So they've done a brilliant job giving you a graphic representation of what happens.

    03:09 Remember, it's the baroreceptor reflex, that's the one that can set the rate of your heart.

    03:14 It senses a decrease in arterial pressure.

    03:17 There you see, the little yellow guys attached right to the aorta, so they sense a drop in that pressure.

    03:24 When they sense that drop, they'll send a signal to your brain, to the medulla. So see how they've got them all the way up connected to your brain.

    03:32 Then the medulla sends a signal through the sympathetic nerves to increase heart rate because an effort they want to raise the blood pressure.

    03:40 So when we put patients on a vasodilator, it's this baroreceptor reflex that will cause them to -- have that superfast heart rate response.

    03:51 So they sense that drop in arterial pressure, the baroreceptors send a signal to the medulla.

    03:57 The medulla sends a signal to the sympathetic nervous system, and your heart rate goes up.

    04:02 So to, kind of, deal with this, sometimes, we have to put patients on vasodilators on beta blockers.

    04:08 Remember, when the sympathetic nervous system sends those signals down, it will attack -- it will connect, not attack, it will connect to those receptors on your heart, right, the beta 1 receptors and make it beat faster, unless we give you a beta blocker, like metoprolol.

    04:26 This can help prevent that reflex tachycardia that's brought on by this barrel receptor reflex.

    04:32 Now I want to walk through that again with you just briefly.

    04:36 How does a beta blocker help us deal with that reflex tachycardia? Well, the deal is, when that sympathetic nervous system is stimulated, it's going to send a transmitter to those beta 1 receptors on the heart, whose job is to make the heart beat faster.

    04:51 But see, a-ha! You've given the patient metoprolol, so that drug has already filled up those beta 1 receptors.

    05:00 So when those transmitters come and try to tell the heart rate to go faster, it won't happen because you've already medicated the patient with a beta blocker.

    05:09 Now, the increase in blood volume, that's kind of a weird one, right? We've got a picture of a blood pressure cuff meeting right there. You see, it's 140.

    05:17 That's too high. We know that we want your blood pressure to be much lower than that.

    05:22 But when you have increased volume, you're going to have an increased blood pressure.

    05:27 So, how can a vasodilator drug that dilates give you increase blood volume and sometimes a higher blood pressure? Well, the answer is our friend, aldosterone.

    05:39 I've talked about that before. Aldosterone is a hormone, and it's a hormone that tells my body to hang on to sodium.

    05:48 When my body hangs on to sodium, then you know what follows, water.

    05:52 So, aldosterone is a hormone that is a chemical messenger.

    05:58 Tells my body to hang on to sodium.

    06:00 When you hang on to sodium, water follows.

    06:04 That means you've got an increase in volume.

    06:07 Aldosterone leads to sodium retention.

    06:10 Sodium retention leads to reabsorbing more water in your kidney, so your volume goes up.

    06:17 When your volume goes up, so does your blood pressure.

    06:20 So if my blood pressure over a long period of time is low, because I've been taking vasodilators, the body's going to pick up on that and it might stimulate aldosterone to be released.

    06:32 So the more aldosterone my body puts out, the more sodium and water I retain.

    06:38 So just like we used beta blockers to treat that reflex tachycardia, we can use diuretics to help minimize that extra volume and make sure we're getting the effect we want from the vasodilators, which is the decreased blood pressure.

    About the Lecture

    The lecture Risks of Vasodilators (Nursing) by Prof. Lawes is from the course Cardiovascular Medications (Nursing). It contains the following chapters:

    • Risk of Vasodilators
    • Falls Risk
    • Reflex Tachycardia
    • Baroreceptor Reflex
    • Increased Blood Volume

    Included Quiz Questions

    1. Elevated heart rate
    2. Decreased heart rate
    3. A direct decrease of arterial blood pressure
    4. An indirect decrease of arterial blood pressure
    5. A decrease of oxygen in the blood
    1. An increased release of aldosterone
    2. Long-term lowered blood pressure
    3. Sodium and water retention
    4. Increased blood volume
    5. Increased blood sugar

    Author of lecture Risks of Vasodilators (Nursing)

     Prof. Lawes

    Prof. Lawes

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