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Step 5: Acid-base Imbalance and Compensation – ABG Interpretation (Nursing)

by Rhonda Lawes

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    00:01 Okay, so now you know step 1,2, 3 and 4.

    00:06 So in step 1,2 and 3 - we figured out where we are, step 4 - we figured out whose fault it is.

    00:12 Now give me a little picture there of an evil guy so we think of him as the villain, that means whose fault it is.

    00:19 Steps 5 and 6 will look at how the body's responding so we need the body to respond in a way that's helpful, a way to compensate for that imbalance.

    00:28 That's why he has a little superhero cape on and a big letter on his chest, right? so there's our hero.

    00:34 They were looking to see if the body has responded in a way that's beneficial or helpful to get that pH back to normal.

    00:41 We know the kidneys control the bicarb, the lungs control the CO2.

    00:46 So if we're having a respiratory issue we look to the kidneys to help us.

    00:50 If we're having a metabolic issue, we look to the lungs to help you.

    00:54 Okay, don't rush there without concept.

    00:56 Right, if I'm in or respiratory acidosis, that means my pH is too acidic, right? So I'm gonna look to the kidneys, the opposite system to see if they're working in a way that actually helps me.

    01:09 Well if I'm acidic I need more or less bicarb? Right, I need more bicarb.

    01:17 So if those kidneys are working in a way that helps me, that bicarb level needs to be greater than normal.

    01:24 So it needs to be greater than 26, that way I will know that the kidneys are trying to help.

    01:30 Okay, because remember you either have a villain who cause the imbalance or we're looking at the opposite system to see if it's responding in a way that's actually helpful in getting that pH back to normal or homeostasis.

    01:43 Remember if the lungs cause the problem, we look at the metabolic or the kidney value to see if it's helping us in a way that will move that pH in the right direction.

    01:52 If the kidneys are the problem, we look at the lungs to see if they're reacting in a way that helps us get us back to a normal pH.

    01:59 So you do steps 1 through 4 on your own, pause the video, we'll be back to talk about the answers.

    02:10 Okay, welcome back.

    02:12 Let's see if your labels match ours on the screen.

    02:16 pH of 7.25 is lower than the normal pH of 7.35 so we labelled it acidotic.

    02:23 Now CO2 of 55 is more than normal, right? because the normal CO2 level is 35 to 45 so we label that acidotic because we have excess CO2 in the blood or extra acid.

    02:37 Now a bicarb of 22, bingo! that is right in the line, right? It's 22-26 so we're still within normal.

    02:46 So we label the pH acidotic, we label the CO2 acidotic.

    02:51 Because step 4, you do the pH matchup, we know its CO2 is the problem and lungs control the CO2 so this patient is in respiratory acidosis.

    03:05 The pH told us where we are - acidosis, whose fault it is is the lungs because the lungs control the CO2 levels.

    03:12 So we're in respiratory acidosis, cool.

    03:17 Now we need to look at, we know that it's the lungs' fault that's why our villain has a set of lungs on his chest to remind you: respiratory acidosis means the lungs are the bad guys, they're the ones that got us there.

    03:31 So now we're seeing if the body is responding or compensating.

    03:35 That's what's compensating means, hey the body's out of balance we're looking at the opposite system, see if it's compensating.

    03:42 We will see if we have a hero because we know who the villain is, now we're gonna look at the opposite system to see if it's responding in a way that helps.

    03:51 Now before we go forward, I want you to take a good educated guess.

    03:56 If we're in respiratory acidosis, we know that it's the lungs' fault, right? and we're gonna look at the opposite system to see if it's helping.

    04:06 Well the opposite system is the metabolic system.

    04:11 So what type of change do we need to see from the metabolic system to help us move from respiratory acidosis back to a normal pH.

    04:22 Do I need more bicarb or do I need less bicarb? You make your guess, pause the video but write it down, you gotta commit to an answer.

    04:32 So the question is, if the body is really compensating or responding in a way that's helpful to respiratory acidosis, is the bicarb level higher or lower than normal? Okay, got your answer written down? Hang on to that, we're gonna walk through some different steps, let's see if you got it right.

    04:56 So when we're talking about compensation, we already did steps 1, 2, 3 and 4, right? We know that we're in respiratory acidosis.

    05:05 That means the lungs are the ones that got us here, that's why the villain has a set of lungs on his chest.

    05:10 That's got there because we have an elevated CO2, we have extra acid in our blood.

    05:15 That's what made the respiratory acidosis.

    05:18 We can back that up because the CO2 level's 55, we know that's too high.

    05:23 Now, how can we ge tback to normal, we look at the opposite system, right? That's the kidneys, now what do the kidneys control? Sweet! Bicarb, that's what the kidneys control.

    05:37 So we asked what would the kidneys need to do to help us move an acidotic pH closer to normal? Would we need more bicarb which is basic, or less bicarb? Well hopefully your answer said, Right - more bicarb.

    05:54 So in order to move a pH that's too acidotic back to normal, we need extra base or move towards alkalosis in order to become normal, so we need a higher level of bicarb So you're looking at that opposite system and seeing if the values are outside of the normal range in a way that's helpful.

    06:16 So in respiratory acidosis, I'd be looking for a bicarb that is greater than normal or greater than 26 Okay, I promised that will make more sense as we keep trying some more examples If it's not, if that bicarb had not been outside of normal in a way that's helpful, then it's not compensation.

    06:39 But if it is outside of normal, if it's greater than 26 but the pH is still not normal, we call that partial compensation - it's like, hey you're getting there but you're not quite there.

    06:53 The reason it's partial compensation is because the pH is not back within normal range The pH is still acidotic but we see that the kidneys have been able to respond in a way that's outside of their normal values and it's helpful.

    07:09 That's partial compensation.

    07:11 so when the lab values of the opposite system are within normal range, it is on compensated respiratory acidosis or whatever one of the four is.

    07:22 So the lab values of the opposite system if they're not outside of the normal range in a way that's helpful, we consider it to be uncompensated.

    07:33 Look at this example.

    07:34 I want you to decide if you think it's compensated or not.

    07:37 We're in respiratory acidosis, you look at the opposite system - the bicarb is 22, which is normal.

    07:44 Is this compensated? No, it's uncompensated.

    07:52 The bicarb would have needed to be greater than 26 in order for this to compensated.

    07:58 So this is uncompensated respiratory acidosis.

    08:03 Now before we go on pause and make sure, pretend you are teaching someone else, give your rationale for why this lab value is uncompensated respiratory acidosis.

    08:14 I want you to talk through those answers before we go forward Okay, even pretending that you're teaching someone is a great way to check your level of understanding of the concepts.

    08:30 If there's something you're not clear on, stop right here, go back and review those steps again, then make sure that's clear in your own mind.

    08:37 Because that 5th step is to look at the opposite system.

    08:41 So if I'm saying the lungs, the opposite system is the kidneys.

    08:45 If I'm saying metabolic, the opposite system are the lungs.

    08:48 Now remember the lungs have the faster and bigger impact than the kidneys.

    08:53 The lungs can respond in change of respiratory rate and volume and you'll see a bigger change in your CO2 than when the kidneys try to deal with the bicarb level.

    09:02 They're trying, it just takes a lot longer for you to see a big impact on that.

    09:06 So the opposite system is the one where the responder compensate.

    09:10 In respiratory acidosis we want the kidneys to increase the bicarb Acidosis means a more acidic, bicarb is a base - that's why I need more of it.

    09:20 if I'm in metabolic acidosis, the opposite system would be the lungs.

    09:25 So I'm gonna need the lungs to respond in a way that has less CO2.

    09:29 So the only things the lungs can do, is breathe faster.

    09:34 Now, here's one really cool example, so hang with me.

    09:37 Have you ever heard of diabetic ketoacidosis ? Yeah, that's what happens when a type I diabetic, when their blood sugar just goes crazy high.

    09:49 Diabetic ketoacidosis is a form of metabolic acidosis.

    09:54 Now there's a certain sign that goes along with DKA - we call it the Kussmaul's respirations.

    09:59 They breathe like this.

    10:03 and this gets really weird, sweet-smelling breath.

    10:06 Now you know why.

    10:08 That's one symptom you have to memorize because diabetic ketoacidosis is a form of metabolic acidosis that means I'm in acidosis cause it's the metabolic system's fault, but my blood sugar is way high, so I look to the lungs to see if they're helping.

    10:25 Kussmaul respirations are the body's attempt to blow off CO2 because the body recognises the pH is often DKA and it's trying to get you back to homeostasis.

    10:41 The only the lungs can help, is to try and get rid of as much acid as possible That's why they blow off CO2 and you have Kusmmaul's repirations.

    10:49 See that's the cool part, once you do the work of understanding lab values, it's gonna open up a whole new world for you and looking at what's going on to your patients and helping them be safe.

    11:00 Now here's our next example.

    11:02 I want you to do this again on your own, so pause the video, we'll come back and talk through it after you're done Alrght, does this match your labels? The pH was acidotic, the CO2 was alkalotic, the bicarb was acidosis, so you did steps 1 through 5, the bicarb and the pH match, so this is metabolic acidosis.

    11:27 Remember we talked through that other example that DKA is just one example of a metabolic acidosis.

    11:33 So we know where we are - we're acidosis.

    11:36 We know whose fault it is that we got there - it's metabolic system or the kidneys.

    11:42 Now we're gonna look at the other systems, see if it's responding in a way that's helpful.

    11:46 Okay, so I'm in acidosis, I need less acid, my CO2 is 32 that's less than normal.

    11:53 Sweet! That means I am in partially compensated metabolic acidosis because the lungs are responding in a way that's helpful.

    12:04 The CO2 level is outside of the normal range and it's lower than normal -that's what we wanted.

    12:11 so this person is in partially compensated metabolic acidosis.

    12:16 Good deal, now try the steps again with this example.

    12:24 Do yours match ours? pH is acidotic, CO2 is acidotic, bicarb is alkalotic so when you did the pH matchup, we're clearly in respiratory acidosis.

    12:37 When you do step 5, you look at the opposite system.

    12:40 Normal is 22 to 26 (mmol/L), this is 34 so that means I have extra bicarb.

    12:48 If I'm in respiratory acidosis will extra bicarb help move my pH in the right direction? Yeah, it sure will.

    12:57 my pH is still off so I'm in partially compensated respiratory acidosis.

    13:04 Good job!


    About the Lecture

    The lecture Step 5: Acid-base Imbalance and Compensation – ABG Interpretation (Nursing) by Rhonda Lawes is from the course Interpretation of Arterial Blood Gases (ABGs) (Nursing).


    Included Quiz Questions

    1. Respiratory acidosis, partial compensation
    2. Respiratory alkalosis, no compensation
    3. Metabolic acidosis, partial compensation
    4. Metabolic alkalosis, no compensation
    1. Metabolic alkalosis, partial compensation
    2. Metabolic acidosis, no compensation
    3. Respiratory acidosis, no compensation
    4. Respiratory alkalosis, partial compensation
    1. Metabolic acidosis, partial compensation
    2. Metabolic acidosis, no compensation
    3. Respiratory alkalosis, partial compensation
    4. Respiratory acidosis, no compensation
    1. Respiratory acidosis, no compensation
    2. Respiratory acidosis, partial compensation
    3. Metabolic alkalosis, no compensation
    4. Metabolic acidosis, partial compensation
    1. Respiratory alkalosis, partial compensation
    2. Respiratory acidosis, no compensation
    3. Metabolic alkalosis, partial compensation
    4. Metabolic acidosis, no compensation
    1. Respiratory acidosis, partial compensation
    2. Metabolic alkalosis, no compensation
    3. Respiratory alkalosis, partial compensation
    4. Respiratory acidosis, no compensation

    Author of lecture Step 5: Acid-base Imbalance and Compensation – ABG Interpretation (Nursing)

     Rhonda Lawes

    Rhonda Lawes


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    Great Video!
    By Mark M. on 23. September 2020 for Step 5: Acid-base Imbalance and Compensation – ABG Interpretation (Nursing)

    Explained the process very well! Definitely helps out when trying to find out what is going on in the patient.

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