Symptoms and Causes of Low Blood Pressure (Nursing)

by Rhonda Lawes, PhD, RN

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    00:02 Now, we talk about the opposite end of this spectrum, we just talked about high blood pressure.

    00:06 I want to talk about low blood pressure, that's also called hypotension, which is pretty easy to remember, because high blood pressure is hypertension, so low blood pressure is hypotension.

    00:21 So, the problem comes at when I don't have enough blood pressure, that means I'm not moving enough of the oxygenated blood around in my body to adequately take care of all my cells and tissues and organs.

    00:34 So, when my blood pressure is too low, I have inadequate tissue perfusion.

    00:40 I don't get enough oxygen to my organs and my tissues.

    00:43 So, be very clear as we step through, why is low blood pressure such a big deal, because if it's low enough, then I'm not getting good tissue or organ perfusion, you're not going to feel good.

    00:54 Let's talk about the things that you start to feel.

    00:57 The patient might become, kind of, dizzy and lightheaded and they could even faint.

    01:03 They won't be able to really think clearly because, again, their brain is not getting perfused.

    01:10 They might have some vision changes and get kind of blurry or can't really focus on things.

    01:15 Their skin is going to become very cold and clammy.

    01:17 Do you know why? So, super cool thing that your body does.

    01:21 When the body says, "Whoa, blood pressure is low," it tries to shunt all the blood toward the most important things; your brain and your heart.

    01:30 So your skin gets cold and clammy because… it shunts everything away from fingers and toes and extremities into the trunk, and particularly selfish, is the heart and the brain.

    01:41 So that's why the extremities get cold and clammy.

    01:44 You're also going to feel pretty nauseated, that's not a real warm feeling.

    01:48 When someone's blood pressure is really low, that's going to be problematic.

    01:52 I actually was hospitalized 1 time for a pulmonary embolism.

    01:56 They didn't know that at the time, but my blood pressure was in the 60s, and that is the absolute worst nausea I've ever experienced.

    02:06 I've never taken chemotherapy, but that nausea would come over me like a wave, and I have never experiencing anything like it before or since, nor am I interested in experiencing anything like that.

    02:18 But low blood pressure can cause some really significant nausea.

    02:23 Of course, you are going to be pretty tired and you say just don't have the energy.

    02:27 Sometimes, even patients who had previously had a high blood pressure and we put them on antihypertensives to lower their blood pressure, they can feel the same things.

    02:37 They can feel kind of tired and fatigued as we go through it.

    02:41 But these are definite symptoms that a patient will feel if their blood pressure is too low to perfuse the tissues and organs in their body.

    02:49 So you want to recognize, we almost have more symptoms for low blood pressure that the patient can actually feel and report to you, than we do for high blood pressure.

    02:58 Some people actually may tell you things that they normally feel with high blood pressure, but usually, the patient can relate to the symptoms of low blood pressure and can communicate those to you much more clearly than high blood pressure.

    03:10 So how do you end up with low blood pressure? Well, think back to what we know about blood pressure.

    03:17 2 things: cardiac output and systemic vascular resistance.

    03:22 So, as far as cardiac output goes, if the heart rate is lower, we call that Brady, meaning slow, cardia, slow heart.

    03:31 So if you have a lower heart rate, that can cause your blood pressure to be low.

    03:36 If you have a significant decrease in blood volume, hey, those are 2 factors that are significant with cardiac output.

    03:43 So, if I have less volume on board, I'm dehydrated, maybe I took a diuretic, maybe I was… I had extended vomiting or severe diarrhea, you know, anytime you have a high fever for a long time, you're vomiting, or you have severe diarrhea, you're losing lots of fluid.

    04:03 So, fevers for a long period of time cause you to be dehydrated.

    04:07 Vomiting, you're losing lots of fluids and not usually taking much in.

    04:12 And in severe diarrhea, you're losing a lot of fluid in your stool that you normally would not.

    04:18 So, these 3 things can make you extremely dehydrated.

    04:23 Most at risk population for dehydration would be our very young and our very old.

    04:27 They can become dehydrated even quicker than an average, middle-aged, healthy adult.

    04:32 So, I'm going to always watch a patient who I think is severely dehydrated for signs of low blood pressure.

    04:39 Now, if you live in my state, it's really hot where I live, and when those kids are out doing 2-a-day football practices, they have to be on them like crazy to make sure that they're replacing the fluid that they're losing because of the heat and because of the exercise.

    04:54 Otherwise, they're going to end up with heatstroke, which definitely involves a very low blood pressure because they have low volume on board.

    05:02 On top of that, we've talked about diuretics.

    05:04 Those are drugs that encourage fluid loss, and that's usually for a good reason.

    05:08 We use diuretics often…remember, those are drugs that encourage fluid loss.

    05:13 We use diuretics for people with high blood pressure.

    05:16 Because think back to what you know about blood pressure, cardiac output and SVR.

    05:21 If I have less volume on board, I have a lower cardiac output and a lower blood pressure.

    05:27 So using an appropriate amount of diuretic is a really good way to bring blood pressure down.

    05:32 But sometimes, if that ratio gets off a little bit, that can really drop their blood pressure.

    05:38 Now, there's medications…other medications that can cause low blood pressure.

    05:42 If we have you on a blood pressure medication, an anti, against, hypertension medication, that may drop your blood pressure too low.

    05:51 So I always say, anything a drug can do well, it can also do over well.

    05:58 So we put you on an antihypertensive and now you end up with low blood pressure.

    06:02 Nitroglycerin is a vasodilator.

    06:05 Now you may know someone who's on nitroglycerin.

    06:08 Sometimes, they have patches that they wear.

    06:11 They take them off at night, so they don't build up tolerance.

    06:13 They have little tiny pills that they carry with them in little brown glass bottles, so the light doesn't get to them, and they put them…underneath their tongue.

    06:22 But that's a vasodilator.

    06:24 Anytime I make the diameter of the vessels bigger, you've got some issues.

    06:29 Now, this doesn't go after arteries.

    06:30 Nitroglycerin goes after your veins.

    06:33 And what happens is blood kind of pools and hangs out here, and not as much blood comes back to my heart.

    06:39 So it makes your body feel like there's less volume.

    06:42 So when someone takes nitroglycerin, it should lower their blood pressure.

    06:47 Other vasodilators will do the same thing.

    06:50 You end up with more blood staying out here, less is coming back to the heart, so that's why you end up with a lower blood pressure.

    06:56 So there are medications that can cause your patient to have low blood pressure.

    07:01 There's another term, orthostatic hypotension.

    07:06 That's where a person who…either low volume or they're on a blood pressure medication.

    07:12 If they're lying down and they sit up too quickly, or if they jump up and stand up too quickly, they're going to…the room starts to spin.

    07:19 That's orthostatic, depending on their position, hypotension.

    07:24 It takes our body a minute to kind of readjust.

    07:27 So when you're having patients that are on antihypertensive medications, kind of want to recommend to them, "Hey, if you're laying down, sit up slowly and wait for a couple seconds just to make sure you're acclimated, and then stand up slowly and give yourself a couple seconds just to make sure that you're not dizzy because of that orthostatic hypertension."

    About the Lecture

    The lecture Symptoms and Causes of Low Blood Pressure (Nursing) by Rhonda Lawes, PhD, RN is from the course Pharmacology and Implications for Nursing. It contains the following chapters:

    • Symptoms of Low Blood Pressure
    • Causes of Low Blood Pressure

    Included Quiz Questions

    1. Diuretics
    2. Calcium Channel Blockers
    3. Vasodilators
    4. NSAIDs
    1. Orthostatic
    2. Malignant
    3. Benign
    4. Accelerated
    1. Light-headedness
    2. Vision changes
    3. Loss of consciousness
    4. Paralysis
    5. Seizures
    1. Heart
    2. Brain
    3. Liver
    4. Kidneys
    5. Skin
    1. Decrease systemic vascular resistance
    2. Increase systemic vascular resistance
    3. Decrease cardiac output
    4. Decreases cardiac oxygen demand

    Author of lecture Symptoms and Causes of Low Blood Pressure (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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