Nonstress Test (NST) (Nursing)

by Jacquelyn McMillian-Bohler, PhD, CNM

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      Slides Fetal Monitoring Basics Nursing.pdf
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    00:01 Okay, we've talked about the fetal heart rate, we've talked about how to measure contractions; let's put it all together in a usable form, the way we might see it in labor and delivery.

    00:13 We're going to talk about first a test called a nonstress test.

    00:18 Now, maybe you've heard of a stress test.

    00:20 If you've worked in cardiac at all, you may have heard of a stress test where someone gets on a treadmill and runs, they have electrodes all over their chest and then we look at the ECG to see if there are any changes on their heart rate pattern.

    00:34 Well, the same thing happen when we're not necessarily running, but we're just moving.

    00:39 So we want to know what's going on with the fetus if it's just laying there.

    00:44 What does Clitus do when there's no activity? Well, if he's just moving his arms or legs or doing anything like that, the heart should respond and we want to be able to see that on the heart rate monitor to make sure every thing's okay, so we do what's called a non-stress test.

    01:00 So we're going to place the toco and the transducer on the abdomen, but we're not going to do anything, so it's actually noninvasive. We use it to determine the level of oxygenation so if the fetus is doing fine and the blood flow is good, then we're going to see a normal heart rate, we're going to see variability, we're going to see accelerations and it will let us know that everything looks good.

    01:26 We can also see what the fetus' response is to its own movement.

    01:32 So if the fetus is not well oxygenated, it either might not move or if it moves we won't see the compensatory mechanism of the acceleration so we're looking for that. It's also performed during the third trimester, so again, think about the fact that we had to have neurologic maturity in order to really see that play between this parasympathetic and sympathetic nervous system, so that tends to be closer to the end of pregnancy.

    01:59 We also may find that we use this test if there's a complication.

    02:04 So let's say we're concerned about hypertension or we're concerned about gestational diabetes and its effect on the fetus and we want to make sure everything is okay, we may order a nonstress test in order to test to see if the fetus is getting sufficient oxygen.

    02:20 And finally, it can be performed to confirm well-being in general.

    02:25 So whether it's labor, whether it's complications, whether perhaps the patient has gone past their due date, and we just want to make sure everything is good inside, we may order a nonstress test.

    02:37 Okay, I'm going to change the slide and I want you to think about when might an NST be ordered by the provider? So, this is a test, so I want you to get out your pencil and your paper and actually right this down and we'll take a pause, right here so you can do that.

    02:59 So what did you come up with? Hopefully, you have something written down about medical history or just to check if the fetus is doing okay.

    03:07 Maybe during labor or maybe for a client who has preceded past their due date and we just want to check in and make sure that fetal oxygenation is as it should be.

    03:17 Hopefully, that's what you have.

    03:19 So let's think about the interpretation. So let's look at this strip again.

    03:23 So when we think about an NST and what we know about the NST is that if it is reactive then we have a strip that has a baseline heart rate that is within normal range, that we have variability that is moderate and that we have two accelerations that are 15 beats above the baseline for at least 15 seconds, they'll be two of them within a ten minute period, sometime within this trip.

    03:50 Okay, let's see what we can do with what we have right here.

    03:54 So the first question we have is, what is the baseline fetal heart rate? You got it, it looks like it's about 125. If you said 130, that's perfectly fine.

    04:09 Remember that the number has to end in 0 or 5.

    04:13 The next questions is, what is the variability, so how does the line move? Did you come up with moderate? I absolutely agree, this is moderate variability, another sign that things are looking good.

    04:30 The next step we have is thinking about the accelerations, do you see two accelerations within a 10 minute time period sometime within this strip that meet the criteria of 15 by 15, 15 beats above the baseline for at least 15 seconds.

    04:53 You got it. We circled all of the accelerations here on this strip so that you can see them, they're definitely more than two, so this gets a thumbs up that it is reactive.

    05:03 Now maybe you looked at the bottom of this strip and you said, hey, I see some circles at the bottom, what is that? So remember, we have an external monitor on at this point and so anytime the baby moves or kicks, it's going to set off that toco, so what you're actually seeing is fetal movement and so if you'll notice really closely, if you look at the bottom line and the top line you'll see that they are happening at the same time, so what does that tell us? That tells us when the baby moves, we're seeing accelerations in the fetal heart rate which confirms that this is a reactive NST.

    05:40 Again, thumbs up that everything is going really well.

    05:43 Now, let's look at the strip again, what's missing? Well, let's start in the correct order.

    05:52 First, let's look at the fetal heart rate. I still see about 130, is that what you're getting? Great.

    06:00 What about the variability? Moderate, exactly. Are those two things good? Yes. They are, that's absolutely correct.

    06:10 Now, the next step is to look for those accelerations.

    06:13 Do you see at least two accelerations that are 15 beats above the baseline for at least 15 seconds? No, I don't see that.

    06:27 Now, maybe you said, I wonder if this fetus is less than 32 weeks, would a 10 by 10 accelerations would be okay? Do you see that? No, we don't see that either. So this is definitely a nonreactive NST, and to further illustrate the point, if you look down at the bottom graph you see those circles indicating fetal movement and there are no acceleration that correspond with that, so what that tells you is that then this NST is nonreactive.

    07:02 Now, what are the important thing to realize is that a fetus has a sleep cycle, they're not awake all the time. Thank goodness. And so sometimes they may be resting.

    07:12 They still may be moving around a little bit, but they may be asleep; and when you're asleep your neurological activity is not as active, so sometimes we may have sleep periods that last up to 20, 30, 40 minutes, where the baby is not very active and you're not going to see the accelerations and it doesn't mean that the baby is not okay.

    07:30 So if we don't see those accelerations within the 20 minute period, we might extend the NST up to 40 minutes to try to capture that information.

    07:40 So we're not going to call a strip nonreactive until we waited at least 40 minutes.

    About the Lecture

    The lecture Nonstress Test (NST) (Nursing) by Jacquelyn McMillian-Bohler, PhD, CNM is from the course Fetal Monitoring (Nursing).

    Included Quiz Questions

    1. It may be ordered in response to a noted complication or problem.
    2. It is used to measure uterine contraction.
    3. It is used to determine fetal heart tone.
    4. It is performed during 1st trimester.
    5. It is an invasive procedure.
    1. NST might be ordered by the provider to check if the fetus is doing OK.
    2. NST might be ordered by the provider after labor.
    3. NST might be ordered by the provider to determine uterine contraction.
    4. NST might be ordered during 1st trimester of pregnancy.
    5. NST might be ordered by the provider to check the well-being of the mother.
    1. If there are 2 or more FHR accelerations reaching a period of at least 15/min (bpm) above the baseline rate, lasting at least 15 sec from onset to return to baseline in a 20-minute period.
    2. If there's no acceleration reaching a period of at least 15/min (bpm) above the baseline rate lasting at least 15 sec from onset to return to baseline in a 20-minute period.
    3. If there's 1 acceleration reaching a period of at least 15/min (bpm) above the baseline rate lasting at least 15 sec from onset to return to baseline in a 20-minute period.
    4. If the baby moves and there's a deceleration on the FHR.
    5. If the baby doesn't move and there's an acceleration on the FHR.
    1. Normal baseline fetal heart rate is less than 110 bmp
    2. A reactive NST is when the baby moves, and there is an acceleration on the fetal heart rate.
    3. NST is used to determine FHR response to its own movement.
    4. NST can be performed during the 3rd trimester.

    Author of lecture Nonstress Test (NST) (Nursing)

     Jacquelyn McMillian-Bohler, PhD, CNM

    Jacquelyn McMillian-Bohler, PhD, CNM

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