Physiologic Changes in Pregnancy: Cardiovascular System (Nursing)

by Rhonda Lawes, PhD, RN

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    00:01 Okay, you can't talk about pregnancy unless you think about the physiological changes.

    00:04 So growing a human is a big job and there are significant changes to a woman's body during pregnancy.

    00:12 Yeah, I bet I didn't need to explain that to you, right? Just from what you visually observe, you can see there's significant changes but there's a lot of internal changes and it affects drugs so let's look at the changes that can impact drugs disposition and its dosing.

    00:28 So we talked about the significant changes.

    00:30 I kinda look at the cardiovascular, respiratory, renal, and GI changes.

    00:36 I took the major ones and grouped these into these 4 categories to make it easier for you to remember.

    00:41 Kind of give you a framework to bounce that off of.

    00:44 So let's look at cardiovascular first.

    00:47 Okay, they definitely have an increased heart rate.

    00:50 Remember, there's a lot going on here metabolically.

    00:53 There's a lot of energy going to grow in this baby.

    00:55 Their heart rate is going to be higher when they're pregnant.

    00:58 Their body is working harder than it is before they're pregnant.

    01:01 They're also gonna have increased renal and uterine blood flow.

    01:05 You need that. Those kidneys are working harder, the heart's working harder, your uterus is definitely more functional when it's growing a human.

    01:13 Now the last one, I want you to keep in mind because the inferior vena cava and it can be compressed by the uterus so as that baby grows, that big heavy uterus can kinda compress that inferior vena cava.

    01:27 If a pregnant woman tells you she suddenly feels dizzy, consider that that's being compressed and that's why she suddenly feels dizzy because not as much blood is returning to the heart.

    01:40 That's what makes her dizzy. So pregnant women, left side.

    01:43 Pregnant women, left side. Pregnant women, left side.

    01:48 Now why did I do that 3 times? Because repetition is the key.

    01:52 Now, why would I turn a pregnant woman on her left side? Well, think what would happen to the uterus if I turn a pregnant woman on her life side.

    02:00 Right, so she's on her left hip.

    02:03 That uterus is gonna come off of those vessels a little bit, allow more of the blood flow to return to the heart.

    02:10 So I'm gonna increase preload.

    02:12 That's a good thing because that's gonna increase her overall blood pressure and she's not going to be as dizzy.

    02:18 So pregnant women, left side.

    02:21 You got it but you understand what that does in a pregnant woman's body.

    02:25 Now I'm not talking about 6 weeks pregnant.

    02:27 This is gonna be somebody who's uterus is big enough and full enough to be compressing that vena cava.

    02:33 Now here's some cool chart. I love this. We summarized it for you right there.

    02:38 You see what happens to blood volume? It goes up. Plasma volume? It goes up.

    02:43 Cardiac output? It goes up. Stroke volume? It goes up.

    02:48 Picking up a theme here? Yeah, heart rate, it's up.

    02:51 Now, peripheral vascular resistance, that one goes down and CVP, the central venous pressure is unchanged.

    03:00 So everything goes up except that peripheral vascular resistance.

    03:05 So those vessels are open and things are flowing well.

    03:08 So besides memorizing all these stuff, just kinda get a feel for the cardiovascular overview.

    03:14 It's gonna be working hard, pushing more volume, but doing really well in the average pregnancy.

    03:20 Now I wanna talk about the coagulation factors and fibrinogen.

    03:25 It doesn't happen often.

    03:27 It's not common that this happens during pregnancy but pregnant women are more likely to develop a DVT.

    03:34 Okay, so jot yourself a quick note.

    03:37 Just those 3 letters, D-V-T, because a pregnant woman is a little more likely to develop a DVT than a non-pregnant woman.

    03:46 You think maybe that large uterus during pregnancy may also increase the risk because it puts the veins of the lower body, they get this extra additional pressure on them and so it's harder for that blood to return to the heart so that may be an additional risk.

    03:59 But also, they have an increase in coagulation factors and fibrinogen.

    04:04 Coagulation factors and fibrinogen are what make clots.

    04:10 So pregnant women have a higher risk for DVT than non-pregnant woman.

    04:15 They also have an increase in the coagulation factors and fibrinogen, and they might have that veinous pulling going on down here because of the pressure from the uterus.

    04:25 Okay, so let's talk about these different pressures.

    04:27 I wanna think about what goes on with total body water.

    04:32 Now that's probably a concept that might feel a little uncomfortable for you but hang on, we've got you covered.

    04:38 So a pregnant woman is gonna have an increase in total body water, blood volume, and capillary hydrostatic pressure.

    04:47 That's important to know because in fluid exchange across the capillaries, it uses the hydrostatic and the colloidal osmotic pressure.

    04:57 Now because I have extra total body water, I'm gonna have increased capillary hydrostatic pressure.

    05:03 That's how fluid volume exchange happens across the capillaries.

    05:07 So that's what help us maintain between extracellular and intravascular compartments.

    05:12 So you'll notice that a lot of pregnant women, their feet are puffy, right? Particularly when they carry a baby during the summer time, they can't get their shoes on because their feet can retain water.

    05:24 You'll also wanna watch them closely for that for preeclampsia.

    05:28 Sign of hanging on to extra fluid and significant elevations in their blood pressure could be a sign of preeclampsia.

    05:34 But over across the board, pregnant woman will have an increase in total body water, blood volume, and capillary hydrostatic pressure.

    05:45 We've got a good picture there for you that looks at the osmotic pressure, the hydrostatic pressure, the capillary and how that all works.

    05:52 That's a great reminder for you. So those are all increased.

    05:56 But the serum albumin protein concentration is decreased.

    06:02 Okay, now why is that a problem? Well, serum protein, not serum albumin protein, is what helps me maintain fluid in my intravascular space.

    06:13 Remember, serum albumin is a big molecule, right? And when it attracts the sodium and you know, wherever sodium goes, water follows.

    06:22 So I have a reduced concentration because I have more water.

    06:27 That's another reason why a pregnant woman's feet swell and they end up with edema.

    06:33 You got that uterus pressing down then they've got these issues with the extra total body water, they have less serum protein concentrations, and so fluid shifts more readily out into their tissues.

    06:45 So you're learning a lot about how the body changes because it will impact the drugs.

    06:49 Now some other clinical considerations are thinking about dosage because of what we've just talked about.

    06:56 We know they have an increase in total body water.

    06:59 Here's why we did the work of walking through that because you might need to consider a higher initial and maintenance dose of hydrophilic drugs.

    07:07 Now I know we're getting into some concepts like go ahead and list and list of hydrophilic drugs.

    07:11 Not the point that I want you to focus on right here.

    07:14 I want you to keep in mind, hey, I know mom is gonna have more total body water so if this drug is a hydrophilic drug, I might have to see a change in dosage.

    07:24 That would explain why the health care provider would write larger doses for initial and maintenance doses in order to maintain a therapeutic level.

    07:33 Now, this whole reduced serum albumin protein concentration because of this extra water, I'm worried about fluid volume shifting, but remember that there could be an increase in unbound active drugs because of the lower protein concentration.

    07:48 So we're gonna keep an eye on that because unbound drugs are active drugs.

    07:52 Knowing that this is gonna be an impact, a possible impact for a pregnant patient.

    07:57 Okay, so we've looked at the cardiovascular.

    08:00 There's a lot there.

    08:01 Pause for just a minute and on this slide, before we go to respiratory, just jot down some keynotes.

    08:07 Make sure you can review that so it's solid in your mind before you move on with us to respiratory.

    About the Lecture

    The lecture Physiologic Changes in Pregnancy: Cardiovascular System (Nursing) by Rhonda Lawes, PhD, RN is from the course Medication Safety (Nursing).

    Included Quiz Questions

    1. Lie on the left side
    2. Lie on the right side
    3. Sit up
    4. Lie supine
    1. Increase in fibrinogen
    2. Increased heart rate
    3. Increased peripheral vascular resistance
    4. Increased red blood cells
    1. Increased hydrostatic pressure
    2. Increased total body water
    3. Increased pressure in capillaries
    4. Decreased blood volume
    5. Increased serum albumin
    1. Active unbound drugs are increased
    2. Hydrophilic drugs are administered in lower doses
    3. Medications must be administered intravenously
    4. Unbound drugs are less active

    Author of lecture Physiologic Changes in Pregnancy: Cardiovascular System (Nursing)

     Rhonda Lawes, PhD, RN

    Rhonda Lawes, PhD, RN

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