Selectivity of Vasodilators (Nursing)

00:01 Hi, welcome to our video topic on vasodilators.

00:05 We're going to take a look at drugs that dilate blood vessels.

00:09 Okay, so we're going to start with a question.

00:11 Do vasodilator medications dilate the arteries, or the veins, or both? So before you go on, stop and pick your answer.

00:22 Okay, it was a little bit of a trick question.

00:25 Vasodilator drug groups have 1 of 3 specific targets.

00:29 First one is primarily the arterioles.

00:32 Wait a minute, the question said arteries or veins? Well, arterioles are just the tiniest branches of the arteries.

00:40 So, if we can impact those, if we can vasodilate arterioles, you're going to have a really significant impact on blood pressure.

00:47 It's definitely going to lower your blood pressure.

00:50 So when you see the words "artery" or "arterioles," they're part of the same vessels, just arterioles are those tiny little branches that have a really significant impact on blood pressure.

01:00 The second group are primarily the veins.

01:03 So vasodilator drugs might go after just the arterioles – remember, small branches of the artery -- the veins, or both.

01:12 So, while it was a trick question, we just wanted to open with that to help you know that using these drugs, drugs that make vessels bigger, go after 1 of 3 targets: the arteries or the arterioles, the veins, or both.

01:27 Okay. So, let's break that down a little bit.

01:29 Since we're studying pharmacology, let's put some drug names in there to help you make sense of this.

01:34 Hydralazine is a drug that goes after the arterioles.

01:37 That's when it primarily will open up.

01:40 So if I give you hydralazine, your blood pressure is going to drop.

01:43 Now, when the veins are the target with a drug like nitroglycerin, remember, that's probably familiar to you.

01:50 We give that to patients who have chest pain.

01:52 We can give them a little tiny tablet underneath their tongue, we can give it to them IV, sprays, gels, all kinds of things. But when we give a patient nitroglycerin, we predominantly dilate their veins.

02:05 That'll leave more blood in the periphery.

02:07 We'll talk about what the impact of that is on our next topic.

02:10 A drug like nitroglycerin will vasodilate the veins.

02:15 Now, you're probably pretty familiar with that drug already.

02:17 If you've watched any medical show on TV, you know, we give nitroglycerin for somebody who has chest pain.

02:23 Prazosin will go after both the arterioles and the veins.

02:28 All 3 of these medications will drop someone's blood pressure.

02:32 But I want to break it down for you just a little bit more.

02:34 Don't let these terms frighten you.

02:36 I'm going to explain what they mean, but you'll hear these terms in nursing, especially when you're conversing with physicians.

02:42 So, we talked about hydralazine, dilating arterioles. Remember, those are the tiny branches of the artery.

02:48 And when we do that, you're going to see a pretty big drop in a patient's blood pressure.

02:53 Hydralazine will also decrease cardiac afterload.

02:57 Now, that's the word I didn't want you to be afraid of. Okay, so cardiac afterload is not as complicated as it might sound to you.

03:04 Think about your heart. When it's pumping, if the vessels right outside that heart are tightened down, the heart's going to have to work really, really hard to pump that blood out.

03:15 But if we can dilate those vessels right outside the heart, those arterioles, then the heart is not going to have to work as hard.

03:23 That's what afterload is.

03:25 Cardiac afterload means how hard your heart has to work afterwards as it's pumping blood out to the rest of the body.

03:34 Now if we dilate the veins, like nitroglycerin, it's going to decrease cardiac preload.

03:39 We just talked about afterload, right? That's what happens after the heart, how hard the heart is working.

03:45 But preload is the amount of blood that returns to the heart.

03:49 It's easier to remember if you think about preload means before the heart, pre heart.

03:54 So if my veins are dilated more, the blood kind of hangs out there in the periphery, like kind of down in my legs and stuff.

04:01 So I have less blood returning to the heart.

04:04 That's a decreased cardiac preload.

04:07 Now, when we hit both of those, we -- it's a full game, right? Prazosin or nitroprusside, sometimes you may have heard that called as nipride, those are medications that go after both the arterioles and the veins.