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Acid-base Homeostasis (Nursing)

by Rhonda Lawes

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    00:00 Hi, welcome to our video on interpreting arterial blood gases or as we usually call them, ABGs.

    00:07 I'm gonna show you how in just six easy steps, you'll learn how to interpret these lab values, and know what to do for your patient.

    00:15 Okay, look at this guy, at least from the looks of that foot I hope this is a guy but we're talking about what's the big deal about normal.

    00:23 Look how comfortable this person looks around their couch, at home they got their favorite blanket.

    00:29 Well the big deal about normal is, it's just like homeostasis in your body.

    00:34 That means a state of balance, your body is most comfortable there.

    00:40 That's why I always say, "there's no place like homeostasis".

    00:43 Your enzymes work better, your cells work better just everything functions the way it's supposed to be when your body is in a state of homeostasis Enter the couch.

    00:54 We're gonna take that picture with the guy in the couch, just kick back and relax and apply it to ABGs.

    01:00 So I call this "the couch of homeostasis".

    01:03 Think about it as where your body is most comfortable and the most efficient.

    01:08 So on the couch, we're gonna think of that as a normal pH of 7.35 and 7.45 So in between 7.35 and 7.45, that's a normal pH.

    01:22 Now that's the first value I want you to write down.

    01:25 So right down pH and normal value is 7.35 to 7.45 Now we're using the couch to help you see that that just represents the space between 7.35 and 7.45 that's what the couch.

    01:40 That's what the couch represents.

    01:42 Now normal levels for CO2, carbon dioxide are 35 to 45.

    01:48 Woohoo, I was so excited when I first figured that out because pH of 7.35 to 7.45, it's super easy to remember the normal CO2 35 to 45 (mmHg).

    02:01 Now let's look at the normal bicarb: 22 to 26 (mmol/L) So before we really get rolling, I want to make sure that you've written down those three values: the normal pH, the normal carbon dioxide and the normal bicarb Okay, ready? Let's go on..

    02:20 Now we'ill start pretty slow in the beginning to make sure you really have this concepts down well then we'll pick up the pace toward the end.

    02:28 Okay, so we're talking about the couch of homeostasis right? We talked about pH.

    02:33 T hat's the same pH you did in junior high science labs.

    02:36 Now, I threw up some numbers up there for you because like the pH of Diet Coke is about 2.5 And for a lot of you, that's what's running in your veins, right? pH of blood is 7.35 to 7.45.

    02:49 Now, we know we've got about 7.34 because I wanted to bring up the point that different labs will have different values but for us, we're gonna to stick with 7.35 to 7.45 as being normal Well, there I am sitting on the couch right, right dead center in the middle.

    03:07 7.35 to 7.45 is when you're gonna be the most comfortable.

    03:12 Now before we go on, I want you to pause the video for just a minute, and I want you to write down why do we care about being in homeostasis.

    03:20 Okay, so pause the video.

    03:26 So welcome back.

    03:27 Remember, the reason the body's always wanting to get back to homeostasis is because that's where it's functions the best.

    03:33 That's where our enzymes work, that's where our cells work,that's what everything works the best just like you feel the most comfortable on your own couch back at home.

    03:43 Okay, now you see me moved over to the other side of the couch, right? I'm moving toward the red side or the acidic side that's going to represent less than 7.35 So when we're looking at the pH, if it's less than 7.35, remember that's because you're becoming more acidic.

    04:01 Okay, so I started out in the middle, that was homeostasis in between 7.35 to 7.45 Now we're talking about bodies moving at pH towards acidic, it's less than 7.35 Other end of the couch is greater than 7.45 So when the pH is greater than 7.45, I'm becoming more basic So that's what the couch is gonna represent for us, it's just a way for you to kind of conceptualize what pH looks like.

    04:31 As my pH numbers get bigger, I'm moving toward basic.

    04:35 As my pH numbers get smaller, less than 7.35, I'm moving toward acidic now as I'm moving toward acidic.

    04:42 Now as I'm moving towards acidic, and I get lower than 7.35, we call that acidosis.

    04:49 If I'm getting more basic - greater than 7.45, we call that alkalosis.

    04:56 Okay, these words are starting to sound familiar to you, So we're gonna be talking about the things that force the body towards acidosis or alkalosis.

    05:06 That's what we're looking for.

    05:08 What are the things that change my pH? What causes my pH to go lower or more acidic, or higher and more alkalotic? So let's talk about carbon dioxide.

    05:21 Now the normal carbon dioxide is 35 to 45, right? and that is controlled by the lungs.

    05:32 Remember, you got your hemoglobin carrying CO2 back up to the lungs so you can expel it you can pick up more oxygen and deliver it to the tissues.

    05:40 So carbon dioxide is controlled by the lungs.

    05:44 Bicarbonate is controlled by the kidneys.

    05:47 That's why we've shown you what bicarbonate looks like as a molecule and we've attached it with the kidneys, same thing with carbon dioxide and the lungs.

    05:55 So the first concept we want to make sure you have down solid is, what's the normal pH? Right, 7.35 to 7.45 Now we have carbon dioxide is 35 to 45.

    06:09 In the lungs, control the level of carbon dioxide.

    06:12 Now if I'm hyperventilating, what do you think happens to my carbon dioxide level? Right, it'll go down because I'm blowing off all the CO2.

    06:25 Now what happens if I'm not breathing very much? Let's say I'm on drug overdose and I'm breathing very shallow and not very often.

    06:33 CO2 levels are gonna go up.

    06:36 Now bicarb is controlled by the kidneys.

    06:38 The lungs can respond really quickly just by changing my rate and depth of breathing.

    06:43 Kidneys will try to help but it takes a lot longer for you to see a change in the bicarb.

    06:49 So for now, be clear what the normal pH is - 7.35 to 7.45 You know the normal values for carbon dioxide and bicarbonate.

    07:00 And you should be very clear what controls the CO2 levels - the lungs and what controls the bicarbonate levels, we're gonna say the kidneys but it's the whole metabolic system.

    07:12 Okay, so we're looking at the level of bicarbonate, you already know it's controlled by the kidneys.

    07:18 The more bicarbonate I have, the more alkalotic or basic I become.

    07:24 So when you look at the couch, you see that we've got the two pillows there representing 7.35 and 7.45, The more bicarbonate that's in the body that will shove my pH past 7.45, so the more bicarb, the more basic or alkalotic I become, you tell that by the changes in the pH Now we look at the lungs, remember we talked they can kick in and make a difference a lot quicker.

    07:52 but the carbon dioxide is controlled by the lungs so the more CO2 in the blood the more acidic or basic I'm gonna be? Acidic, good job.

    08:03 So lungs control the carbon dioxide.

    08:06 And the more carbon dioxide that I have building up in the blood,the more acidic I will be.

    08:12 So if we're looking at the couch, which way are you gonna go? this way or that way, right, are you gonna go towards the acidic or the basic? Well if CO2 in the blood, I want you to think about it as an acid, and the increase CO2 in the blood will definitely move me toward acidosis.

    08:30 so we've looked at a normal pH, a normal CO2 level, a normal bicarb level.

    08:37 And we've looked at if we have excess bicarb, our pH will be more basic or alkalotic.

    08:42 If we have more CO2, we'll be more acidotic.

    08:47 Okay, now I told you we'll be going kind of slow because you really have to get these concepts and we will fly to the other ones compare to this I promise but let's do a quick review.

    08:58 In order to determine acidosis or alkalosis, we will primarily look at which 3 values from an arterial blood gas? Pause the video and see if you can write those three down before we go on.

    09:14 Hey, welcome back.

    09:16 And now before we talk about the answers, I just want to encourage you to really take advantage of the times when we recommend or ask you to pause the video and see if you can recall those numbers.

    09:26 I'm not trying to tell you what to do, nobody likes to get bossed around.

    09:31 But I know as an an educational psychologist, it's the best way for you to study as you go.

    09:37 We're gonna give you a better shot at remembering these concepts and making sure you're really solid on them before we go forward.

    09:43 So again, I'm not trying to be bossy and I hope it doesn't feel that way to you but I just want to help you study right in the moment because I know you have precious little time because you're so busy in nursing school.

    09:56 So let's look at the answers.

    09:58 pH, CO2 and bicarb - those are the three things we're gonna look at when we primarily look at the values for an arterial blood gas.

    10:07 Now which organ primarily controls the bicarb level in the body? HCO3 is just a shorthand way to write bicarb.

    10:16 So which organ primarily controls bicarb in the body? Right, the kidneys.

    10:26 Which organ priumarily controls CO2 or carbon dioxide level in the body? Right, lungs.


    About the Lecture

    The lecture Acid-base Homeostasis (Nursing) by Rhonda Lawes is from the course Interpretation of Arterial Blood Gases (ABGs) (Nursing).


    Included Quiz Questions

    1. 7.35–7.45
    2. 7.25–7.65
    3. 4.40–7.50
    4. 7.15–7.35
    1. An increase in CO2, causing the pH to decrease below 7.35
    2. A decrease in CO2, causing the pH to increase above 7.35
    3. An increase in HCO3, causing the pH to decrease below 7.45
    4. A decrease in HCO3, causing the pH to increase above 7.45
    1. pH
    2. CO2
    3. HCO3
    4. Potassium
    5. Sodium
    1. Kidneys
    2. Lungs
    3. Liver
    4. Heart
    1. Lungs
    2. Kidneys
    3. Heart
    4. Liver

    Author of lecture Acid-base Homeostasis (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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