Acid Base Disorders and ABG Interpretation | Introduction

what's up ninja nerds in this video today we're going to be talking about the introduction to acid-base disorders before we get started though please if you guys do like this video you benefit from it you learn a lot from it you enjoy it please the best way you can support us is by subscribing also hit that like button and if you like put a comment down in the comment section also down in the description box we're gonna have links to our social media platforms as well as our patreon if you guys want we're gonna have comprehensive notes that we're continuously adding to that'll supplement this video so go check that out as well as uh some nice illustrations that kristin's also worked on too so go check that out all right ninjas let's get into it all right ninja so when we talk about acid-base disorders we should have a basic understanding of what makes something acidic what makes something alkaline and the terms that get thrown a lot around a lot one of the big ones is acidosis and alkalosis so we need to have an understanding of what these things mean so what does acidosis mean acidosis is the process by which protons are produced in a large amount there's an increase in the proton production so that's all it is so acidosis is there's some process which we'll talk about what are the processes by which this can happen by which there is an increase in the proton production or just the amount that it's actually being present with inside of the body the extracellular fluid so the process by which we increase our proton production is called acidosis alkalosis is just the opposite it's the process by which there is a decrease in the proton production or concentration or there's just less protons with inside of the plasma or the extracellular fluid and there's many different reasons for these now what's important to know is that acidosis the process by which there's an increase in protons can cause the blood to become more acidic how do i know that there is a formula that we utilize a lot ph equals the negative log of the proton ion concentration and it's just an inverse relationship as you have high proton concentration that lowers the ph when you lower the ph in the blood that makes the blood acidic and this is called acidemia so the question is is what is a particular point at which the ph is now considered to be acidic within the blood that's a great question normal ph is between 7.35 to 7.45 so if we're having a lower ph we're less than 7.35 within the blood that's acidemia so it's a ph less than 7.35 take the opposite we now have a pretty straightforward thing here right a decrease in the amount of protons within the body some process by which that happens utilize our good old equation ph equals the negative log of the proton ion concentration simplistic way is its inverse is you have decreased protons that increases the ph as you increase the ph within the blood this makes the blood more alkaline and this is called alkalemia what's the point at which the blood is now alkaline what's normal ph 7.35 to 7.45 so it has to be greater than the upper limit of normal which is greater than 7.45 okay so very important understanding here is that acidosis and acidemia alkalosis and alkalemia are not technically the same they're commonly sometimes thought that they're interchangeable but acidosis is the process by which you make the ph lower in the blood alkalosis is the process by which you make the ph higher within the blood now the next thing is that we've talked a lot about protons influencing the ph of the blood but there's also two other molecules that we have to talk about that influence the ph there's this equation that happens all the time in our body our bodies are constantly undergoing metabolism breaking down glucose oxygen and producing co2 in water so this is a constant byproduct of cellular metabolism so when co2 and water combine there's an enzyme that you guys really want to know and it's called carbonic anhydrase it's present in certain cells and membrane borders that converts it into carbonic acid carbonic acid is a very weak acid and disassociates into protons and bicarb the two molecules that i want you guys to think about here is co2 and bicarb we talked a lot about protons right up there let's talk about these two these two have a very significant profound effect on the ph as well how do we determine that this annoying equation that you guys probably thought you would never have to see again since general chemistry the henderson-hasselback equation henderson hasselbach equation says if you want to determine the ph based upon the bicarb and the co2 not just the proton concentration you can use this equation we don't need to know all this let's make our lives really really simple let's not worry about numbers and math and all that stuff let's just do this and you'll see how much easier it is get rid of the pka get rid of the log we don't need that ph is equal to the bicarb concentration divided by the co2 now we got to be a little bit particular here bicarb is in a particular concentration called millie equivalents per liter right where co2 is recorded on a pressure so it's usually millimeters of mercury so i can represent this in concentration but if i really want to be particular which i should be i should put partial pressure of co2 this is a modified henderson-hasselback equation and it prevents us from having to do any math and just use logic so let's just do that instead all right so now we have this this is going to help us big time and i'll show you how it will help us to determine what the primary disorder is is it a respiratory disorder or is it a metabolic disorder let's talk about them down here the first one that i want to discuss here is a respiratory disorder that causes the ph to go low that means it's an acidosis and the cause of this acidosis is a respiratory problem so we call this respiratory acidosis so think about the causes of respiratory acidosis it's really straightforward it's not too hard to think about if my my brain is not firing it's not sending signals that's going to cause a problem my my respiratory center within the brain stem if it's not firing if it's depressed so one reason could be that there is cns depression and there's a lot of different causes for this the other thing is that there's a nerve problem the nerves that are going to the muscles are damaged in some way and they're not sending signals to those muscles my diaphragm to contract or the muscles are damaged themselves so there is a neuromuscular disorder or there's a problem where my lungs are having some type of obstruction and i'm not able to breathe co2 off and say things like copd or obstructive disorders so some type of obstructive lung disease all of these things would cause less co2 to be exhaled out of the body if less co2 is exhaled out of the body what happens to its concentration within the blood it builds up if the co2 concentration in the blood builds up don't worry about this whole equation up here and all that stuff just use this simplified one let's use logic here keep the bicarb constant so we're not even going to focus on this one just put that like you know you don't it's constant but the pco2 is what it's elevated if this if we use this reaction we just put like n here for a constant ph if we use this simplified equation here and we just say that co2 is increasing what happens to this number the ph if this was 1 and you increase the lower number it's going to do what to the ph it's going to lower the ph so the ph in this scenario would be low so if we say this the ph will be low uh ph due to what due to high partial pressure of co2 and we just did it with that modified henderson-hasselbach equation let's think about the other scenario you have an alkalosis the ph is high but it's due to a primary respiratory disorder what is that called respiratory alkalosis okay so respiratory alkalosis let's think about the causes keep it really really simple something that's causing the respiratory centers to over fire and there could be many different reasons for this let's let's just call that cns hyperactivity to label a couple things here if someone's really anxious if someone's having a fever if someone is in pain if someone's taking salicylates um sometimes sepsis a bunch of different things they stimulate that respiratory center and it over fires sends more signals increases your respiratory rate and you breathe off more co2 the other situation here is that if somebody is having hypoxemia and what hypoxemia is is that there is low oxygen delivery to your tissues so let's say that someone is having pneumonia and they're not getting oxygen to cross over that infected area or they have a lot of edema pulmonary edema oxygen is not crossing that area where there's a lot of fluid there or they have a pe a clot and there's not even though you have proper maybe ventilation blood can't get to that area of the alveoli to put oxygen into the blood either way what happens what do you think you would naturally do if your oxygen levels in the blood are low breathe more because if you're breathing more you're going to breathe in more oxygen hopefully but what's the consequence of that as you bring in more oxygen you breathe off more co2 so if you're either increasing your stimulation or whether it's due to some cns stimulation or because of a hypoxemic drive you're blowing off more co2 and what happens then if you blow off more co2 the co2 concentration within the blood will decrease use our simplified hinders and hassleback equation this is a constant what happens to the pco2 it lowers use this equation what would this tell us if this number is lower the denominator then the ph will go up so this will tell us that the ph will increase because due to a low partial pressure of co2 pretty straightforward right all right next thing let's say that we have an acidosis but it's due to not a respiratory problem it's a metabolic problem and there's so many different reasons for this we're not going to get into crazy detail but if there's an acidosis and it's not due to a respiratory problem it's due to a metabolic problem this is called metabolic acidosis so a metabolic acidosis the problem is that your body is either retaining a lot of bi uh protons you're not excreting the protons or you're losing a lot of bicarb those are the two primary reasons so let's think about this let's not worry about the protons let's think about the bicarb in this scenario what's happening to our bicarb it's lowering use your equation here if we keep pco2 constant and we do what to our bicarb we lower the bicarb if the bicarb decreases what happens to the ph then the ph will decrease because again the top number is going to determine that so if this happens your ph will decrease due to low bicarb okay all right so before we start talking about some of the causes for metabolic acid is we know that it's usually due to an increase in proton concentration or decrease in bicarb there's something else that we have to talk a little bit about real quick and that's something called an anion gap because that can actually separate our acidosis into two types of flavors so an anion gap anion gap you can determine based upon this equation so anion gap we'll put it as a g here is equal to the extracellular cations the most abundant is sodium we don't really care about potassium because it's mainly intracellular the next one is you're going to do what you're going to subtract this from the pertinent anions within the extracellular fluid and this is going to be chloride and then your bicarb and what happens is the remaining amount that makes up this gap so you're taking sodium you're subtracting the chloride and the bicarb the remaining amount is the anion gap and the anion gap is a measure of particular types of organic acids organic acids that we don't really include in this equation if the anion gap is less than 12 it's considered to be a normal anion gap metabolic acidosis we sometimes refer to that as a nagma if the anion gap is greater than 12 then that is called a high anion gap metabolic acidosis but we just call that agma so that leads to the whole question here is what are the different causes for someone having a normal anion gap metabolic acidosis or an anion gap metabolic acidosis because they're causing an increase in proton in the blood or a decrease in bicarb without going into too much detail because we'll go into these in more detail in individual videos let's use a nice little mnemonic to help us to remember this so for agma anion gap metabolic acidosis you can remember the mnemonic mud piles and the causes behind this is usually due to methanol poisoning or ingestions uremia due to significant kidney injury or renal failure diabetic ketoacidosis propylene glycol ingestions i is going to be for iso isoniazid which is you know someone one of the drugs that you give in tuberculosis l is for lactic acidosis e is for ethylene glycol and s is for salicylates and this is just your aspirin the other type of metabolic acidosis which causes an increase in protons or a decrease in bicarb that has a normal anion gap less than 12 is called a nagma and the causes for this can be remembered by the mnemonic hyper chloride emia and this is sometimes whenever you give a lot of people like a lot of normal saline or hypertonic saline and another one you can remember is if you really want to add this on i'm not going to write it out it's called hyperalimentation all that means you're giving them a lot of food through their alimentary canal what would be a condition where you do that where you're giving somebody tpn so sometimes you can also add into this tpn which is called hyper elementation the other one is a right so in a this problem is an issue with acetozolamide there's a drug called acetazolamide and acetozolamide can actually cause a lot of bicarb loss from the kidneys the other one is called a renal tubular acidoses and we're not going to go into a lot of detail because there's a bunch of different types of these and they can either lead to kind of a a loss of bicarb as well all right the next one is actually going to be diarrhea and diarrhea you lose a lot of bicarb and that's one of the reasons for acidosis the other one here is called a ureteral diversion sometimes if someone has a connection between their ureter and between a part of their gi tract they can actually spill a lot of that chloride out as well and then the last one here is a pancreatic fistula and again you lose a lot of bicarb through that way as well okay so these are some of the big reasons for someone developing a metabolic acidosis primary thing to remember is that there's a low bicarb high protons and it could be due to an anion gap that's elevated or an anion gap that is normal okay the last type of primary disorder is a alkalosis but it's not due to a respiratory disorder it's due to a metabolic disorder so this is called metabolic alkalosis now metabolic alkalosis if we utilize our nice little you know modified henderson-hasselbach equation here what would we say the pco2 is going to be constant but the bicarb what happens in alkalosis that means that the protons are lowered and you have a lot of bicarb bicarb is our base right so if there's a lot of bicarb it's going to make the blood more alkaline so this is going to be increased use the simplified equation if the top number's high ph is going to be high so in this condition here ph is going to be high due to a what a high bicarb okay or a low proton concentration now for these situations there's a bunch of different causes to keep it relatively simple for us let's kind of use the mnemonic vomit okay vomit is guess what the first one is vomiting when you vomit guess what you spill a lot of out protons there's a lot of hydrochloric acid you're spilling a lot of acid you're losing acid o is you're actually over correcting somebody on the vent so over correction of what's called hypercapnia and we're not going to go into great detail of this we'll talk about it in an individual video with the respiratory system and metabolic system but over correction of hypercapnia the next one here is m and this is remembered by mineral corticoid excess and what is this this is just whatever somebody's producing a lot of aldosterone right and there's a lot of different conditions one of the big ones is con syndrome right the other one is iatrogenic um giving them some type of bicarb so iatrogenic one of the common reasons is that we would give someone sodium bicarbonate and you could do this for a bunch of different reasons you're trying to preserve their kidneys for contrast induced nephropathy or they have kidney failure so sometimes if you give them sodium bicarbonate that could also be a cause there because you're giving them bicarb increasing their bicarb and the last one is that you have a total volume loss and this could be in a bunch of different situations so if someone's dehydrated they're losing blood they're having laxative abuse and they're pooping out a lot of their actual bi chloride or another situation would be that they are on taking a diuretic and they're just losing a lot of volume that way so these would be some reasons why someone could develop metabolic alkalosis so this covers kind of our basis and our primary disorders now let's talk about the complications of acidosis and alkalosis so we should have an understanding of why it's important to know about acidosis and alkalosis like what does it do to us like what's the problem why should we be so scared of it it does have a lot of you know problems and complications that it can cause and the particular organs that you want to remember big ones is the heart and the lungs your central nervous system and then there's some metabolic effects that we'll also talk about that can become very problematic as well so let's say over here on the left side of this let's talk about what acidosis can do to these organs okay and then over here on this side we'll just compare and we'll talk about what alkalosis can do to these organs okay same thing so acidosis when there's a lot of protons what it loves to do is really affect the myocardium the contractility of the myocardium and decrease the contractility of the myocardium if you decrease the contractility of the myocardium you decrease stroke volume if you decrease stroke volume you decrease cardiac output and if you decrease cardiac output you decrease your blood pressure or your mean arterial pressure the other thing it does here is it also acts on the smooth muscles within your arterials okay and when it acts on the smooth muscles on your tears it actually causes them to dilate so it causes vasodilation if you cause vasodilation what does that do to the diameter it increases the diameter of the blood vessel and that decreases resistance if you decrease your total peripheral resistance what does that do to your blood pressure it lowers your blood pressure the cumulative effect of decreasing cardiac output and decreasing the total peripheral resistance will have a cumulative effect on causing hypotension and then sometimes this can even lead to shock so important to be thinking about that the other thing is with acidosis it can cause a lot of arrhythmias like re-entrant kind of tachycardias and one of the big things it does is it agitates that myocardium and can lead to v-tac okay so a lot of v-tac can happen here as well there's one more thing i thought was really interesting when i was researching this is that when you have a lot of acidity and someone's becoming hypotensive what do you give them when you give them fluids what's the next thing you do you give them pressures to cause those vessels to clamp down so that they're not becoming hypotensive and people who have really bad acidosis they're resistant to pressers and so that's another interesting thing is that sometimes if you have to go up on the pressure dosage think about are they acidotic so sometimes a big one to remember i thought this was really interesting is that it can cause resistance to vasopressors all right cool now take and compare that with alkalosis there really is no like a superb effect on the contractility so we're not going to talk about that one so no real big effect here for the contractility aspect but there is an effect on the total peripheral resistance just do the opposite here it actually causes arteriolar vasoconstriction that narrows the diameter increases the total peripheral resistance so the next thing here is heart rate you'd probably say oh it's going to decrease the heart rate it actually doesn't it still agitates the myocardium and can cause those actual uh tissue cells to fire those myocardial cells to fire a little bit faster and so it actually can cause some pretty nasty arrhythmias particularly v-tac and even severely v-fib sometimes even svts as well so we'll even put that down sometimes it can even trigger some svts so either way these are big things to remember for the consequences or complications of acidosis and alkalosis on the cardiovascular system what about on the lungs it's really simple if someone's acidotic what is the goal that means that they have a lot of co2 in the blood you want to breathe all that co2 off so breathe that co2 off by increasing your respiratory weight rate what's the complications of that if you're breathing breathing breathing breathing all the time what's going to happen to your muscles you're just going to get fatigued and you're going to get really weak and so this can cause an increased work of breathing we'll put that as d wob and then what this can do is this can lead to increased fatigue and sometimes if this isn't reversed it can cause the patient to go into respiratory failure so in alkalosis think about this in the opposite scenario and someone has alkalosis they have low co2 within the blood what are you going to want to do you're going to want to build that co2 up how do you build the co2 up you lower your ventilation rate you lower your respiratory rate if i lower my respiratory rate what's the problem with that though yeah i might build up the co2 but guess what i'm not bringing in oxygen because remember with tidal volumes yes you could breathe out the co2 i mean you could retain co2 with less respiratory rates but you're not going to bring as much oxygen in and this can lead to hypoxemia and this can become a problem okay the next thing you have to think about is the metabolic effects what i like to remember is that protons and potassium kind of go hand in hand so in this situation in acidosis what happens is there is going to be a lot of protons okay when there is a lot of protons the protons will want to shift when there's a lot of protons they'll want to shift from the extracellular outside of the cell into the cell and whenever they do that there's a little pump here that also transports potassium out and so whenever the protons are brought into the cell you push potassium out of the cell what is that going to do yeah you may increase this reaction here and what is that going to do to the potassium it's going to increase the potassium if i cause an increase in potassium what is that called hyperkalemia and hyperkalemia can be very bad and cause a lot of arrhythmias the other thing is this can actually a lot of these protons can affect your pancreas too believe it or not particularly the hormone made by your pancreas you know your pancreas makes a particular hormone called insulin and what insulin does is it works on tissues and tries to be able to perform a lot of metabolic functions to lower your blood glucose levels so let's pretend here i put like a tissue cell right here and insulin's going to act on that tissue cell guess what the protons do they affect and alter the activity of insulin being able to work on these tissue cells and so now insulin can't exert its full effect on these tissue cells and what is that called that's called insulin resistance and so what would happen to the person's like blood glucose levels they would go up right and so that's another thing to be thinking about compare that over here so just use the opposite effect here potassium magnesium they kind of also shunt a little bit too so for this situation think about the same scenario if there's less protons less of those protons will be shunted into the cell less potassium ions will leave the cell so what happens to the potassium outside the potassium level outside the cell will decrease the same kind of mechanism but to a lesser degree can happen with magnesium so the same reaction here can also happen with magnesium so if less protons are going into the cell less magnesium will be leaving the cell and so the magnesium levels within the blood will also drop this last one is a little weird okay there is a protein that's made within our blood called albumin okay so here's our albumin albumin has a lot of like negative charges around it and it loves to bind onto protons okay but if you have alkalosis how many protons do you think you'd have less protons and so some of these protons will bind onto this albimum but leave a lot of negatively charged spaces left over so who do you think is going to want to bind onto that and neutralize that negative charge calcium and so calcium will bind a lot of that will bind onto these negative charges and the calcium that's actually free or circulating in the blood the ionized calcium let's actually be really specific here let's put ionized calcium the amount of it's freely circulating is low because a lot of it is bound to albumin all right cool the last thing that you guys need to remember here is with respect to the central nervous system the effect is pretty much the same here where if you have a lot of acids what that does is that really affects the cerebral volume like cell regulation and what it does it can lead to a lot of an altered mental status and particularly even lead to coma okay if there's a lot of acids there and the opposite if someone has alkalosis it also can lead to an altered mental status but it can also cause the neurons to be a little bit more agitated and fire a little bit more than they should and if they're firing a lot more than they should what is the condition in which neurons are firing erratically not you know not under control seizures so sometimes this can trigger seizures or tetany but again it can also lead to coma so big big consequences if acidosis and alkalosis are not corrected now we can try to correct this by giving certain drugs or treating the underlying disorder but our body is so beautiful that it does something to try to fix this on its own if it can and this is called compensation your body will try to compensate for this acidosis and alkalosis how does that happen let's talk about that all right so let's talk about these compensation mechanisms so how our body tries to deal with an acidosis or alkalosis kind of scenario on its own all right so let's say that we take the first situation here where we have someone who is in respiratory acidosis okay respiratory acidosis and they're going to try to compensate now acutely how they'll compensate is that the buffer system that bicarbonate carbonic acid buffer system will kind of try to kick in and buffer it acutely that's a pretty quick reaction but it's not going to produce a very significant change in the ph so what happens is our kidneys are going to be the primary way that we try to compensate when there's a respiratory disorder the problem is though when the kidneys compensate it takes a decent amount of time so what will happen and whenever there's high co2 what does that do to the ph think about it right it makes the ph do what it drops the ph so what happens is this signals our kidneys and our kidneys will take some time so i want you to remember that this mechanism by which our kidneys compensate takes a long time it's not quick it can take hours to days sometimes even longer than that how would we deal with this well think about it think about it really simply if your ph is low how would your kidneys try to deal with that well think about it if the ph is low let's think about the two ions that we haven't talked about here which also influence the ph protons and bicarb if i want to do the opposite which is increase the ph what will i do to my protons i'll try to excrete more protons in the urine and i'll try to reabsorb more bicarb into the blood that makes sense right the problem is though is that this takes a decent amount of time to occur but once the person starts to compensate and let's say that they have a respiratory acidosis a chronic one they may also have a high bicarb and that comes into the abg's when we interpret them so big thing to remember their kidneys compensate for respiratory acidosis by excreting protons and retaining your bicarb okay let's go to the next situation here next situation here is we have a respiratory alkalosis so in a respiratory alkalosis what's the problem you're building uh what's happening to the co2 it's low right so you have low co2 within the blood if there's low co2 within the blood what does that do to the ph you use that equation right low co2 will do what to the ph it'll increase it so this is going to increase the ph how do we deal with this other than the co2 we deal with it via the protons and we deal with this via the bicarb and again who deals with this over a long period of time your kidneys take some time your blood will try to buffer it acutely but it's not going to produce a significant change so how we change this think about it ph is high we want to increase the ph so what will happen to the reabsorption of bicarb are we going to reabsorb as much bicarb as we usually do no decrease your bicarb reabsorption what about the proton excretion are we going to excrete as many protons no you don't want to you want to try to retain some of those protons so retain the protons a little bit by not excreting as many of them if there's less protons that are excreted more will kind of build up in the blood that'll lower the ph if you're reabsorbing less bicarb less alkaline or less base within the blood that's also going to drop the ph okay next situation here you have a person who is in metabolic acidosis and i only reason i say this because i can see that the protons are going up right quick easy way and i have my kidney here so metabolic acidosis okay so when someone's in it and someone's in metabolic acidosis what do i know look at our bicarb using our henderson hassleback equation the bicarb is low what does that do to the ph lowers the ph so if i lower the ph what is this going to do what happens is is this stimulates respiratory centers it stimulates your central nervous system and then your central nervous system will go and stimulate an increase in what your respiratory rate why because if you increase your respiratory rate what are you going to do let's say i increase my respiratory rate i'm going to breathe off more co2 if i breathe off more of that co2 how much of the co2 will be left within the bloodstream less there should be less because i'm breathing most of it off so co2 within the blood should be low utilize our equation here to see the change if our co2 is low what happens here bicarb let's just not worry about that right now kind of pretend it's constant for a second and your your co2 is dropping that's your compensation what happens to the ph it will go up your problem was an acidosis you're trying to change it by getting rid of that co2 and making the blood a little bit more alkalotic so this would be the compensation mechanism is by getting rid of more co2 which causes co2 levels within the blood two drop all right so the last scenario here is going to be metabolic alkalosis the only reason i can tell you that is i can see here that my protons are going down quick easy way to know that this is an alkalosis and then i have my kidney here and not my lungs that are the problem so metabolic alkalosis in this situation right i have less protons i have more bicarb use our little trusty equation here bicarb goes up what happens to the ph the ph will also go up right so if the ph is going up what will this do to your respiratory system well it's telling you that your ph is really high i don't really want to do anything to my co2 i don't want to breathe it off right i actually kind of want to retain that co2 so instead of me stimulating the respiratory center like i did here i'm actually going to inhibit the respiratory center so that i don't actually stimulate the muscles that are going to be controlling my breathing as much so i'm going to lower my respiratory rate if i lower my respiratory rate i don't breathe off as much co2 instead a lot of that co2 will build up within the bloodstream and as the co2 builds up in the bloodstream use our little trusty equation here what happens pco2 goes up what happens to the ph it goes down and that is how we try to compensate because we try to retain co2 which makes the ph go down because originally the ph was high the big thing to remember here is that whenever your kidneys are trying to compensate that takes a long time but whenever your lungs are trying to compensate for a primary metabolic disorder this is a short amount of time this can happen in minutes okay so remember that that this is a short amount of time it doesn't take near as long as the kidneys do to compensate for the primary disorder so now that we understand the different primary disorders the complications the compensation mechanisms let's determine how we can interpret an abg and let's do some practice problems all right ninja so we've built up a pretty good foundation up to this point on kind of like understanding the basis of acid-base disorders so what i want us to do is let's say that we get an abg because you guys get these questions a lot whether it's your nursing school pt school pa school medical school you get these questions and you have to be able to interpret abg's i'm going to take you through the easiest way that when i look at abgs on a daily basis how i interpret them so the first thing that we do is we have to have an abg right comes up and you get your ph i need to determine based upon that ph if there is an acidosis or an alkalosis but particularly right if the ph is low it's an acid it's acidemia and if the ph is high it's an alkalemia so first thing i look at is is this ph less than 7.35 because if that's the case this is in acidemia and if the ph is greater than 7.45 then that's a alkalemia now you guys here's something really interesting let's say that you check the ph and it's normal you'd probably be like oh there's no acid-base disorder just move on that's not always the case there can be what's called compensation that we just talked about so just because the ph is between 7.35 to 7.45 it still could still may be abnormal i there still may be an abnormal disorder present and you have to still go through these steps to make sure that there's not an actual abnormal disorder with a compensation mechanism present so that's the first thing i look for what's my ph after i look at my ph i look at my pco2 now the pco2 is really really important because this is going to help me to determine if this is a respiratory disorder or a metabolic acid disorder so i like to use my equation that we had before so you can remember ph is equal to the bicarb divided by the pco2 so the first thing i want to look at is what's the direction of my pco2 and how do i remember that let's do this in two ways right i have two equations here and i see in one of these my pco2 is high and over here i see that my pco2 is low if my pco2 is high what would that do to the ph the ph would then be low and over here the ph would then be high so what i like to remember there's like a little mnemonic it's called s'more so there's a little mnemonic i'll put it over here it's called s'more and this is kind of an easy way to remember it where metabolic disorders the ph and the bicarb move in the same direction and then respiratory disorders the ph and co2 move in opposite directions so that's kind of an easy way to remember that so if you see the co2 and the ph are moving in opposite directions you know that it's most likely a primary respiratory disorder okay now sometimes the co2 could be normal as well and again maybe that's a compensation mechanism that's going on so again just because it looks normal doesn't mean that there isn't actually a disorder present bicarb use your same type of equation here use your modified henderson hassleback ph is equal to the bicarb divided by the pco2 ph is equal to the bicarb divided by your pco2 and the same thing we're not worried about the pco2 right now we're worried about that bicarb how is that affecting the ph so remember s'more it's the same or you can just use this equation right so let's say that i increase my bicarb or i decrease my bicarb what would that do to the ph this would increase the ph causing an alkalosis this would decrease the ph causing a acidosis so you can either use this equation or use this little mnemonic to help you to remember that all right so i've determined the ph if it's acidotic alkalotic or normal i determine if my co2 correlates with that ph in opposite directions or if my bicarb correlates with that in the same direction after i've done that the next thing i need to determine is if there is a metabolic acidosis then what do i need to go about and do i have to determine my anion gap remember i told you that when there's a metabolic acidosis you can have a high anion got metabolic acidosis or a normal anion gap metabolic acidosis so how do we calculate that do you guys remember we take and utilize the equation anion gap is equal to and we kind of abbreviate this ag is equal to the sodium minus the chloride plus the bicarb and what this tells us is the amount the anion gap is the amount of unmeasured anions primarily organic acids if the anion gap is less than 12 this is a normal anion gap metabolic acidosis if the anion gap is greater than 12 that is an anion gap metabolic acidosis and this is where you got to go and figure out what the cause of it is which we talked about with those mnemonics over there all right the last thing we have to determine is the delta ratio if someone has an anion gap metabolic acidosis if they have an agma only so if there is an agma which means that their anion gap is greater than 12 then you have to do this delta ratio and the reason why is they could have an anion gap metabolic acidosis with an underlying concomitant other disorder like a metabolic alkalosis or a non-angote metabolic acidosis so you have to look for this to determine if there is a concomitant disorder okay so how do we do this you do utilize you do you utilize what's called the delta ratio and the delta ratio is a formula and what you do is you take the anion gap that you measured so let's say that you measured your anion gap you calculated off of what you got from your your bmp so your measured anion gap minus the normal anion gap that you would have which is 12. okay and so we'll just put here 12. you're going to divide that by your actual bicarb particularly the normal bicarb so your normal bicarb it comes in a different range and we'll write all those down for in a little bit in a second but your bicarb it's going to be around 24. and then you're going to subtract that from your measured bicarb what you got from your uh your abg okay when you do that you're going to get a couple different things okay you're going to get some numbers what you need to know is if the delta ratio comes there's two different there's three different things you want to know if it is less than one if the delta ratio is between one and two or if your delta ratio is greater than two if the delta ratio is less than one that means that this is a pure anion gap metabolic acidosis there is no other concomitant disorder present if the delta ratio is greater than one but it's less than two that means that there is a mixed agma and nagma present okay and the last thing is if the delta ratio is greater than 2 that means that there is actually not just an agma but there's also an underlying metabolic alkalosis and an agma present okay so go through these steps one by one check the ph correlate it with your co2 your bicarb based upon if it's going in the same bicarb co2 opposite if there is a primary metabolic acidosis check your anion gap see if it's elevated if it is greater than 12 it's an agma if it's less than 12 it's enagma if you have an agma you have to do the delta ratio to see if there's a concomitant disorder based upon this equation and whatever you get will tell you what that mixed combination is the last thing i have to mention here is what some of these normal values are because you're like i don't even know what the heck normal is so we know what the normal ph is right that's pretty simple we can just mark that down real quick normal ph is 7.35 to 7.45 right that's pretty straightforward the pco2 is somewhere between 35 to 45 millimeters of mercury so if it's less than 35 that's low co2 higher than 45 high co2 pretty straight forward right the bicarb concentration is usually between 22 to 26 milli equivalents per liter and that's where i got that uh 24 is if you go between these two it's 24 all right and then just a quick review for anion gap if the anion gap is less than 12 that is considered to be a normal and i gap if it's greater than 12 it's an elevated anti-gap all right so i think we have a basic understanding of how to kind of have a system to go through these abg's let's actually go through some practice problems and try to see if we can figure them out now the best way i think to truly understand acid-base disorders is doing practice problems it really helps to kind of solidify what we learned now the first one i give you i'm kind of messing with you a little bit but it's it's an important point to gain from this okay let's start with our kind of step-by-step process first thing we check is the ph is it normal or is it low or is it high it's normal you're like zach what the heck already you're giving me a disorder that there's there's no actual disorder remember what i told you just because it's normal ph does not mean that there's a primary kind of hidden abnormality present let's kind of still go through this then even though it is normal the ph is it on the upper limit of normal or is it on the lower limit of normal in this kind of situation it's closer to the upper limit of normal let's make our lives a little easier then let's say that the ph it's not high but in respect to normal it's on the upper limit of normal my co2 what's normal levels 35 to 45 that's way beyond 45. so my pco2 is high what's my bicarb it's 37 normal is 22 to 26 it's way beyond 26. so my bicarb is high remember the either the equation or that thing s'more if it's ph and bicarb are going in the same direction it's metabolic if the ph and the co2 are going in opposite directions it's respiratory it's going in same direction it's a metabolic disorder and it's a metabolic alkalosis because it's a ph that's high so it's a metabolic alkalosis now the next thing that you have to determine is we didn't really talk about this a lot but we kind of described compensation mechanisms when someone has metabolic alkalosis their ph is high what do you try to do your lungs will try to do what slow down its breathing so that you retain co2 and that's going to take some you know it can happen over time where it can become a chronic kind of thing but what happens is eventually you'll compensate for this so look what happened the pearson co2 started rising and it rose up so much that it was able to bring the ph within the normal range so this means it's a metabolic alkalosis with full respiratory compensation now what would be a partial then because i know that's what you guys ninja nerds are asking a partial compensation would mean that the pco2 is still going up it's high but the ph is not within normal range okay boom roasted let's move on to the next one all right first thing check your ph is the ph high low or normal well it's way less than 7.35 so in this case the ph is low what's my pco2 it's way greater than 45 so the pco2 is high bicarb it's pretty much on that lower limit of normal but it's still normal so we're just going to say in this case if you really want it to be specific you could say it's low but we're just going to put normal here we're not going to even mess with it we're just going to say normal in this case so in that situation use your kind of mnemonic s'more look at the co2 it's going in the opposite direction of the ph the primary disorder is respiratory is it acidosis or alkalosis the ph is low it's acidosis so this is a respiratory acidosis now the next thing that you could say is okay is there any compensation what would happen if you were in respiratory acidosis what would you do to your bicarb well your ph is low you would want to do what to your bicarb you would want to kind of increase your bicarb right so that you could actually make the ph a little bit higher in this case we didn't really have any change within the bicarb it's not really going up in that case so since the bicarb isn't really kind of going up or changing in this point then there really isn't a lot of compensation so i would say that with this there is no compensation with this metabolic no metabolic compensation so no metabolic compensation okay and again that should make sense where if your co2 is elevated causing the ph to drop you should want to increase your bicarb but it hasn't really gone up much all right next thing here let's go to the next scenario ph 7.32 is it low or is it high it's low so my ph is low next thing i can look at is my pco2 is my pco2 high or low all right so 35 to 45 it's technically a little low right it's it's not really low but it's technically low it's just one point under so we can say that the pco2 is technically low the bicarb 22 is the lower limit it's way beyond that so the bicarb is low okay in this scenario these are going in the same direction so if they're going in the same direction that's a metabolic acidosis okay we know it's a metabolic acidosis so let's put down here for right now a metabolic acidosis remember what i told you there is two types of metabolic acidosis elevated anion gap and normally an ion gap how do i calculate the anion gap i have to take my sodium 135 and subtract it from chloride plus bicarb what does that give me it gives me 12. so my anion gap in this situation is 12 what's the normal anion gap less than or equal to 12. so if i'm less than or equal to 12 that is considered normal so this is a normal anion gap metabolic acidosis do i have to calculate a delta ratio no because it's not an elevated anion gap is there compensation okay there's a low ph right due to a metabolic acidosis if someone is compensating with a metabolic acidosis what would you try to do breathe off co2 if you try to breathe off co2 what should happen to the co2 levels they should drop did it drop enough to bring the ph in a normal range no so it's a it's a compensation but it's not full it's a partial respiratory compensation so with partial respiratory compensation well turn me over and tickle me twist it let's move on to the next one the next one here ph 7.25 what is that that's low baby what's the co2 well it's 35 to 45 that co2 is also low bicarb that's low definitely it's way less than 22. so go to my scenarios here bicarb is low ph is going in the same direction that's a that's in metabolic acidosis we had another metabolic acidosis we're on a roll if i have a metabolic acidosis i have to calculate my anion gap how do i do that 140 minus 77 plus 10 what does that give me that gives me about 53 right so my anion gap is 53 and the whole mama that is a big anion gap it's way greater than 12. and so because of that that is a high anion gap metabolic acidosis with elevated anti-gap metabolic acidosis what do you have to do calculate a delta ratio so if i calculate the delta ratio by taking my anion gap 53 minus 12 divided by 24 minus 10 what do i get i get a delta ratio of about three so my delta ratio is equal to 3. what did i say if it's greater than 2 what is the problem it's a concomitant metabolic alkalosis and anion got metabolic acidosis so this is a mixed with it's mixed with a metabolic alkalosis now if you want to determine if there is any respiratory compensation you could check and if we looked here what would i expect if the ph is low okay that's acidic you're going to try to breathe off your co2 if you try to breathe off your co2 the co2 should drop did the co2 drop it did did it do it enough to bring it into a normal ph range no so is it a full composition or partial it's a partial compensation so if you really wanted to add that on there's also partial respiratory compensation this was definitely a beast okay if you can get this one you can probably get any of them okay all right next scenario ph low high normal that's normal right it's 7.35 to 7.45 so it is technically normal so it's a normal ph for helping us to understand this though is on the lower limit of normal or on the upper limit of normal it's on the lower limit of normal so let's to make our lives easier it's the ph is low co2 way greater than 45 so the pco2 is elevated bicarb is usually 22 to 26 it's way greater than 26 so bicarb is elevated use the thing smore if it's moving in the same it's metabolic if it's moving opposite it's respiratory definitely respiratory and the ph is low so it's a respiratory acidosis all right next thing look at your bicarb in a respiratory acidosis your ph is low what are you going to try to do you're going to try to increase your amount of bicarb you're going to try to retain bicarb or reabsorb more bicarb did we reabsorb bicarb yes because the bicarb went up did it do it enough to keep the ph in a normal range yes so is this a partial compensation or a full compensation it's a full compensation because it brought it within the normal ph range so respiratory acidosis with full metabolic compensation beautiful next scenario here you have a ph that's equal to 7.28 that's low so we have a low ph the pco2 35 to 45 way less than that so the pco2 is going to be low and then the bicarb is way less than 22 so that is going to be a low bicarb use your mnemonic s'more if it's moving in the same direction it's metabolic which it is so this is a metabolic acidosis what do we do with metabolic acidosis disorders we calculate an anion gap we calculate the anion gap by doing what you take 129 subtract from 100 plus 11. what does that give you that gives you about like um 18. then if it's 18 that's definitely greater than 12 so that is definitely an elevated anion gap metabolic acidosis what do we do with elevated anion gap metabolic acidosis we calculate a delta ratio the delta ratio will tell us if there is a concomitant disorder so we take 18 minus 12 divided by 24 minus 11 and that gives you about 0.5 so the delta ratio is less than one if it is less than one it is a pure let's add that on there a pure anion gap metabolic acidosis with no concomitant disorders associated with it the next thing we have to determine is is there compensation if there is an acidosis the ph is low your body tries to compensate by breathing off the co2 so it'll try to lower the co2 did the co2 lower yes it did did it do it enough to bring the ph into normal range no so is it full composition or partial compensation it's partial so there's also a partial respiratory compensation ninja nerds we have just completed our complete understanding of how to get through acid-base disorders [Music] you

Channel: Ninja Nerd

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Keywords: Ninja Nerd Lectures, Ninja Nerd, Ninja Nerd Science, education, whiteboard lectures, medicine, science, arterial blood gas, ABG, acid base disorders, acidosis, alkalosis, respiratory acidosis, respiratory alkalosis, metabolic acidosis, metabolic alkalosis

Id: vv8AyBcC3Ok

Length: 58min 8sec (3488 seconds)

Published: Mon Apr 19 2021