Interpretation of ABG #2

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Interpretation of ABG #2

27 Jun, 4 PM

[Music] good evening everyone uh hi dr ucha welcome you all on behalf of team netflix uh we are back with one interesting metric select blockbuster with dr sally bendray whoever has joined newly for session uh series pulmonologist and transplant physician practicing at max super specialty hospital global hospital and masina hospital mumbai uh this is part two of uh interpretation of ebg session that we had done uh two weeks back uh if you want to catch up on that leader you can go back to replay section and catch up over to user with this yeah yeah good evening everyone and it's very nice to interact with all of you again as we all know netflix has finished one year and there was a nice award function also last week which was attended by many of you and a lot of faculty also so today we are going to discuss part two of the arterial blood gases i hope all of you have gone through part one because this is going to be the next part of the blood gas analysis so you have to know the basics of that which are naturally i cannot go through again so we will start off with one of the slides of last time's presentation so that everyone gets a little accustomed to what we are discussing we have discussed many things regarding compensation acidosis alkalosis what is uncompensated what is partially compensated today we are proceeding further so this is a rough formula for correlating the saturation which you see on a pulse oximeter with the po2 or the partial pressure of oxygen in the arterial blood as seen in the arterial blood gas as i said it's a very very superficial and a very rough estimate it won't give a perfect estimate but it is based on what is called as oxygen hemoglobin dissociation curve so it's called as the four five six seven eight nine rule as you can see the numbers over here coming to the ph because today some part part of it we will be spending on understanding acidosis why is it so important and what are the difficulties in assessing the acidosis part so we have already discussed about what is a very very risky acidosis and what is a very risky alkalos is the extremes of the entire part one question which was asked last time by one of you or maybe a few of you was about the base excess because this is also one parameter which is mentioned on the arterial blood gas report from here i would request those who are listening would please take a pen and paper because there would be certain things you would you should write down so that we can have a discussion on it or maybe you can interpret the blood gases in a better form so i would request those who haven't got it please get a paper and a book or a pen and a pen so that you can note things down but so this is the base access which is mentioned as i was saying it is mentioned as b e that is base excess and it reflects only the metabolic component of any disturbance of the acid base status okay so there is metabolic alkalosis then the base excess will be positive and if it is metabolic acidosis then the base excess will be negative so that is the only inference to be drawn by looking at the be mentioned on the blood gas okay and of course you will be naturally going to see the bicarbonates because finally when we try to know about the alkalosis or acidosis we are going to see the hco3 the normal range varies from 20 to 20 22 to 26 and the base excess range has again a minus 2 to plus 2 so more in the plus means more alkalotic more in the negative means more acidotic so that would be the understanding of the base excess now let's go to this blood gas okay on the blood gas which you are seeing is has got four xx diagnostics written on it so just to identify this particular blood gas now go through this blood gas for about five to ten seconds try to note down your findings because your findings are more important than me telling you what this abg says so go through it one by one okay the ph you have seen pco2 you have seen and the bicarbonates also you have seen so what would be the interpretation of this blood gas let's see how many of you can try it out on this particular blood gas any one of you can try out the ph then the pco2 you are seeing and you are seeing the bicarbs also so what can you interpret from this blood gas any one of you can try to answer and or those who are unable to type or write i will just go step by step uh you know to understand it one is seven 7.46 so the ph is alkalotic it is showing alkalosis if you have written it down correctly very good pco2 is 44 so it is on the higher limit of the normal so it is on the higher limit of the normal it is 44. bicarbonates are 31. so bicarbonate 31 means the the alkaline aspect is more the bicarbonates are more you see the be here the base excess is 6.6 so it is suggestive that there is an excessive of the alkaline component that is the bicarbonate so you can gauge here that it is a metabolic alkalosis which is happening it is a metabolic alkalosis and the ph is not compensated means ph is not in the normal range so we will not call it compensated but there are certain formulae to know whether there is a partial compensation which is happening okay so just keep it at this point whatever whoever answered metabolic alkalos is excellent we will talk of this ab joe abg i have labeled it as russian so so that it's a little easy to understand which whose avg are we talking about so this is a abg of mr roshan try to see again in this what is happening as you interpret abg's we are gradually going to go into the formulae of compensation and partial compensation what do you make out from this blood gas the blood gas of mr roshan we are discussing right now so any one of you so ph is 7.499 that means again it is going towards an alkaline ph the pco2 though it is given in kilopascals you can see it is in the normal range because the normal range is mentioned there bicarbonates are 32.3 that means they are high so there is definitely a base excess as you can see it is 8.4 so there is a base excess so even the oceans abg suggest you of metabolic alkalosis i hope all of you are getting it so russians abg is also suggestive of metabolic alkalosis someone mentioned respiratory alkalosis but try to see that the carbon dioxide is normal it is mentioned in kilo pascal so don't go by just the number see the normal range so it is metabolic alkalosis we will go to the next abg i'm going a little fast because there are many things to be yet discussed in an arterial blood gas let's see the abg of mr jack what does the abg of mr jack tell you th is 7.183 pco2 is 44.9 bicarbonates are 16.9 we are talking now of jack's abg mr jacks abg so this is and you can see the base excess the be is minus 11 now you are understanding the basis that format so it is minus 11 that means the acids are increasing the bicarbonates are decreasing so it is suggest you offer metabolic someone has mentioned respiratory acidosis dr deepak is mentioned respiratory acidosis but i think dr deepak you should look at the bicarbonate also it is 16.9 ph is 7.18 so it is going in favor of metabolic acidosis okay so those who have been able to understand this let's try to fight check one more abg before we go on to the formula okay let's go through one more abg and find out what's happening mr manoj the abg of mr manoj now this is something very interesting go slow on that try to analyze consider that you are seeing this patient in the icu or in the casualty patients abg has been advised when you are seeing the blood gas the ph is 7.25 pco2 is 35 bicarbonates are 14.9 the base excess is minus 11 okay so we will just stop at this and remember we have been able to perhaps answer the questions correctly that's why i said take a pen and paper will be coming to some formula which you need to calculate you will have to apply some maths also to this now this abg we have analyzed it as metabolic acidosis i hope all of you have understood this much now let us go to the next slide and try to understand what is the compensation okay let's try to go through that remember that when we say metabolic acidosis the compensation will occur by respiratory alkalosis okay the compensation will occur by respiratory alkalosis here in this abg of mr manoj the ph is not normal so there is no compensation or the it has not happened the compensation hasn't happened so what exactly is compensation so respiratory compensation is the physiologic mechanism okay to help normalize the metabolic acidosis that's the simplest way it can be explained and how do we know is we use the winter's formula so this formula is going to be the backbone if you see any patient with metabolic acidosis the moment you see a patient with metabolic acidosis you need to apply the winter's formula and what does winter's formula give you it gives you the expected carbon dioxide for compensation this will be equal to the bicarbonate into 1.5 plus 8 this will be the formula there will be plus or minus 2 depending because we are going to compare it with the carbon dioxide in the blood gas so expected co2 so if the patient's po pco2 is within the predicted range means the abg report and the expected pocp co2 is the same there is no additional respiratory disturbance if the pco2 is greater than expected in the abg whatever value is there if it is greater than expected this indicates an additional respiratory acidosis so then there are two acidosis happening the metabolic also and respiratory also and if the pco2 is less than expected then there is an additional respiratory alkalosis so this last statement below the red formula is very important so if the pco2 is the same as the pco2 in the abg there is no mechanism of respiration happening at all that means there is no compensation started also if the pco2 is greater than the expected that means there is a additional respiratory acidosis happening now if you have noted this let's go back to this abg which we said was metabolic acidosis let's apply the formula of winter's formula to the metabolic acidosis if you have a pen on paper or if you have extra mobile or it can calculate fast then it is bicarbonate into 1.5 so what is the bicarbonate in this blood gas the bicarbonate here is say 14.9 consider it as a round figure of 15 so you are going to multiply 15 into 1.5 plus 8. so 15 into 1.5 plus 8 please calculate and find out how much will be the answer so the answer comes to 30.5 i hope you people have calculated the answer comes to 30.5 s so it comes to 30.5 that is the expected pco2 but what is the carbon dioxide in this it is 35.3 so what we are getting is that in this blood gas the carbon dioxide which we are seeing is more than the expected pure pco2 means the there is a component of respiratory acidosis also occurring in this blood gas so you will actually have to label this abg as a mixed acidosis it will not be only metabolic it will be metabolic plus respiratory yes so dr shravan has mentioned correctly there is an additional respiratory acidosis going on but you came to know this because you applied the winter's formula to this abg had you not applied you would have said this is a blood gas showing metabolic acidosis and pco2 is low so the body is trying to partially compensate but it is not so it's actually a additional respiratory acidosis which is happening i hope you are understanding if if you are not understanding please put up a query at this point itself because we'll be moving on with the next slide so that you understand what exactly we are talking of mixed acidosis there could be mixed acidosis also when to add or minus 2 so it's uh it is depending if you have got say the pco2 in this blood gas is say 35 and you are getting an answer of 34 then you can you will be taking a plus 2 as 36 or -2 as the range it's a range in which the expected pco2 should be it should it's a range so you can have a plus to the answer or a minus to the answer and that will form the range if the pco2 is above that range that means there is excessive pco2 retention that means there is acidosis so we will yes of course see the winter's formula so winter's formula is a range so as you can see the line below the winter's formula i mentioned if the pco2 is within the predicted range so there is a range and if it is within the range so if your our answer here was 30.5 then the range was say 28 to 32 so if within this range the abg shows the pco2 then we will say there is no compensation no respiratory mechanism happening at all if the pco2 in the blood gas is more than this range then we will say there is not only metabolic acidosis but there is also respiratory acidosis which is happening and if the calculated if the pco2 in the expected sample ex if the you find that the pistol in the blood gas is much less than the range then you will say that there is a respiratory alkalosis so you will start saying that now there is a compensation which is started okay so please remember when to interpret and how to interpret this formula you can see these slides again because there are multiple things as i said but we will go slow and steady on this it is all important to mention and think about blood gases so winter's formula you will naturally get to know and this is the same calculation but in a simpler way mentioned so the blood blood gas calculations here i have put the pco2 the bicarbonates and the base excess also it all means the same and now you're experts in at least knowing which is compensation and which is not not compensation okay coming to the next uh summary of metabolic compensation so there are certain respiratory acidosis which are acute and certain respiratory acidosis which are chronic so please write down this formula you can keep it on a cheat block or you can keep it on your mobile take a picture of it you can apply it whenever you see abg whenever you know the clinical scenarios because as if you start working in critical care if you start working in the icu's you will need to know the clinical history so there are patients who have copd which is a chronic respiratory disease and they have a chronic respiratory acidosis there could be an acute exacerbation and then suddenly the acidosis may worsen so there are formulae to really know how much is the compensation occurring all right so these are just you need to know there are this is kept in a box so that you can have a one two three four kind of a remembering idea to know how much is the compensation but just keep it at this we will once you have finished winter formula we are going to the next part which is metabolic acidosis why are we so concerned about metabolic acidosis we are naturally concerned about metabolic acidosis because it can it can lead to a lot of clinical manifestations right from even nausea there can be severe headaches patients may present with hypotension patient may have muscle twitching acidotic breathing as we say or gasping breathing we say hyperventilation suddenly there is a hyperventilation so you may find all these parameters or clinical signs in metabolic acidosis so did that we come to the commonest acidosis we see as clinicians which is the lactate elevation remember even lactates are mentioned on the blood gas okay lactates are also mentioned on the blood gas so we have to know lactic acidosis we have to know diabetic acidosis we have to know about salicylic acid poisoning there are many parts of acidosis but the common one is of course the hypoxic failure which we see when the patient is admitted with severe pneumonia patient who is admitted with ardas patient comes with the acute attack of asthma so there are many such common conditions which we see even for that matter pulmonary edema cardiac failure sepsis hypotension shock peritonitis so all these conditions land up finally with lactic acid collection and lactates lactic acidosis so as we go through the blood gas we come to a factor known as the anion gap okay anion gap now what's an ion gap it's a calculation it's a calculation which has to be done through the blood gas you need to have the anions and the cations with you so cations are the positive and the anions are the negative and the gap between them is called as the anion gap to make it further simplified the calculated or the ones mentioned in the blood gas came to trying to say those mentioned in the blood gas are sodium and potassium and chlorides and bicarb so chlorides are negative bicarbs are negative and sodium is positive and the potassium is positive so positive will be the cations and the negative will be the anions so get me right and now we go through the calculation of anion gap there are many times you see the ico specialists talk about this is a high anion gap metabolic acidosis so this is a normal anion gap metabolic acidosis you need to find out what are the types of metabolic acidosis because the treatment of both differ why they differ because you can see the high anion gap is actually a result of a net gain of acid and a normal alliance gap is actually a result of a glass of bicarbonates so again mathematics come into picture so normal sodium of 140 potassium was four chlorides of one one four bicarbs of 18 and we see that the normal anion gap is anywhere around 12 and if it is more than that it is high and iron gap so normal ion gap is 12 plus or minus 2 okay write it down note it down or remember it and the high anion gap is going to be more than that what all this it may be a little odd for a science student to understand all this but unfortunately i need to teach you a little bit of the pathophysiology though this slide appears to be very very complex you may skip this slide see later on i don't mind it so you can see it later because it's actually all laws of physics and biochemical neutrality to understand the anion gap and there are many things in it which is uncalculated anions and uncalculated cations so we mentioned that there are few anions which we know fewer cations which we know sodium potassium bicarb chlorides but the reason for this slide to be put up is that there are uncalculated or unmeasured cations and anions which add into this gap which we will never know because they are not mentioned on the arterial blood gas okay so that is the reason but you can read the details later on so we will go to the next one so that it's a little easy to understand yeah so if you have gone through what is a high anion gap metabolic acidosis that means the formula wise then one of the commonest reason is diabetic ketoacidosis the commonest reason is diabetic ketoacidosis we will see what happens exactly in that and how to calculate and how to apply it in treatment also because finally we are concerned with the treatment of the patient so in diabetic ketoacidosis the patient presents with rapid onset vomiting abdominal pain those we have seen these patients have must be have definitely understood the pathophysiology of the lack of insulin decreased insulin and the increased glucagon levels causing the liver to release glucose via glycogenolysis and gluconeogenesis and then subsequently formation of free fatty acids and adding to the acids so there is an entire pathophysiology of diabetic ketoacidosis and that presents with a high anion gap acidosis so what what exactly happens we will of course see in that so for example if we have one more component which comes in uh before we just move on let me tell you i'll try to summarize few things for you one is respiratory alkalosis respiratory acidosis metabolic alkalosis metabolic acidosis in metabolic acidosis what we are discussing right now is the anion gap but before that we discuss what is the winter's formula to know the compensation with the respiratory aspect we are discussing the anion gap because there are causes of high anion gap and normal and angular acidosis but when we say anion gap it means sodium potassium bicarb chlorides not to forget that there are uncalculated anions and cations so if we have understood it till here we come to one more aspect of an abg you see there are so many things in the arterial blood gas it is not only the pco2 and po2 a patient who is cachexic many of our respiratory disease patients are cachexic they are having copd they are having bronchitis they are having anorexia for long duration because of which their albumin level has reduced and if the albumin level reduces it will alter the anion gap okay so if the albumin level reduces it will alter the anion gap so we need to have a formula even for that that the albumin corrected anion gap is equal to an ion gap plus 2.5 into the difference between the normal and the observed albumin you remember this formula if you get a patient who has hypoalbuminemia you would land up see all these clinicians who are listening to me would realize some patient may come to you with tachypnea breathlessness fidel edema and bilateral repetitions but the history is that patient has not been eating well for a few weeks now the federal edema may be because of low albumin it could be of course because of cardiac failure but if there is low albumin even that may alter the anion gap so you need to know the albumin when we are calculating the anion gap so try to remember this formula you should apply it whenever you are seeing these patients and it is very important that you put it into perspective you are going to be uh going to know the history you are going to know the blood gas and then apply so without wasting much time let's go straight to the blood gas now and try to see what's exactly happening in this abg again once more now tell me what is the anion gap in this blood gas i'm sure you people are able to assess the acidosis and the alkalosis but let's see what's the anion gap in this particular blood gas any one of you can calculate the if you want the formula i can it's not it's a very simple formula actually sodium plus potassium minus bicarb minus chlorides so try to see what do you make out from this abg we have already seen this type of acidosis the previous slide someone wants the previous slide okay the formula do we want this formula the formula for the anion gap if anyone wants i will go back to that slide yes so this is the anion gap calculation yes all of you are coming close to the answer and if you remember right when we saw this particular abg when you saw this particular abg some time back now let's see if all of you can put the winter formula also to this i think you should be able to remember we had already checked out this abg and we had said that the ph is uh acidotic the bicarbs are low and when we applied the winter's formula the pco2 in this abg was coming more than the expected pco2 so this abg was suggested actually of a mixed acidosis partly respiratory partly metabolic and if we go to the metabolic aspect and we want to know whether it's a high anion gap or a low anion gap then it is a high anion gap acidosis so this will be a high anion gap acidosis in such situations you should obviously ask them i want to see the albumin because you can correct it further on by applying the formula for the albumin if there is hypoalbuminemia in this abg one more thing to be marked you can see the lactate level the metabolite value there is a mark which is mentioned metabolite values in that the lactate levels are written here so the normal values as mentioned here is point zero two two but in this particular blood gas we can see it as eleven point five so there is definitely a lactic acidosis so coming to the high anion gap metabolic acidosis so there are reasons for it and there is a mnemonic for it so it's it's it's you can make up your own but you can remember this in a different way also come but out of all this what you commonly will see in your practice is those which are right in the center the d the one which is marked as d diabetic ketosis you will see alcoholic ketoad acidosis you will see starvation ketoacidosis you will see so these are very common even methanol poisoning can present with acidosis and carbon monoxide poisoning so as you can see urania that is one of the important reasons of metabolic acidosis where the kidneys fail and there is urania so the acids are the the acids are increasing so there is metabolic acidosis so many of the causes can give rise to metabolic acidosis but these are high anion gap metabolic acidosis and similarly there is a pneumonic for normal anion gap metabolic acidosis now what is off of of specific interest is that most of these causes lead or are related to the abdomen that is the bowels or the diarrhea or the kidneys so there could be renal tubular acidosis there are more with gis problems like bowel fistulas there could be adrenal insufficiencies pancreatic fistulas ureterostomy so as you can mention check here the normal anion gap metabolic acidosis have a little different kind of reasons so if you just try to remember it it would be in terms of a ureterostomy it can be a fistula intestinal tistula renal tubular acidosis pancreatic fistula adrenal insufficiency so there are certain causes which can give rise to a normal anion gap acidosis so these are something like a pictorial understanding as you can see over here even excessive normal saline infusion okay that's a chloride intoxication or hyper elementation renal loss of bicarbonates so there are those specific clinical scenarios you need to pick up and understand if you see a normal anion gap acidosis and to complicate it further i know i don't know how many of you are liking this but to complicate it further and to make a distinction is it a gi cause or is it a kidney cause you can calculate the urinary anion gap okay i'm not going to go into detail a little bit too much for us to but you can actually go into the gi causes and the renal causes of the renal causes of the normal anion gap acidosis so calculate the urinary anion gap okay let's go to the things which we like the most interpretation i think that's the most interesting one for all of us now let us put one two three four into it i want to know from you first of all what is the interpretation of this abc 1 and what is the anion gap in this integer let's see try to find out i i know few people have forgotten the winter's formula so i have kept it purposefully in the next slide again bicarbonate into 1.5 plus 8. this is the winter's formula you need to apply bicarbonates into one point five plus eight so find out how much will be the first you check what is the abj interpretation so how do we interpret this abg let us see first the interpretation of this abg i want you any one of you to tell me please show winter chart again okay here's winter chart dr sanat kumar is saying it is dr sanat please check the pco2 in this for it to be called as respiratory acidosis the pco2 has to increase but here the pco2 is 20.2 yes so dr ashmita is right now what is what was the uh winter's formula expected pco2 which you people got what i got was 24.65 i i i hope each one of you calculated by yourself but here what we can see that the piece you to mention here is less than the pco2 which is coming as the expected which means there is a compensation which has started okay there is a compensation which has started so i would put it as a partially compensated metabolic acidosis partially compensated yes sombra is fine is correct metabolic acidosis with respiratory alkalosis and the respiratory alkalosis is the compensation which is happening so it is method metabolic acidosis with respiratory alkaloids perfect now let's see whether it is what kind of uh acidosis is it is it normal or is it high anaemia so check the sodium 135.5 so 135.5 plus it comes to potassium is 1.7 1.7 minus the bicarbonates bicarbonates are 11.1 minus the chlorides one one zero so it comes to 16.1 so is it right am i correct in checking this everyone has got that as the answer i hope each one of you are trying to do that so dr pradeep when we say complete is only when the ph comes in the normal range this is just the touching the normal range 7.35 so we can say that it is compensating so it is it is it is almost i would say partially compensated because it is not yet come into the normal ph of 7.4 so it is it is obviously going to get compensated right so it's a compensated respiratory metabolic acidosis let's solve one more abg before we move to the next slide oh it's already 109.9 okay so we are still left with 20 minutes so we can continue it further so what do we make of this abg the one which this abg which i am showing you has a ph of 6.461 try to try to interpret this apg the ph is 6.461 uh you will have to again apply the winter's formula to this if you want to go through the winter's formula it is bicarbonate into 1.5 plus 8 so bicarbonate so the expected pco2 comes here as 19.85 i hope all of you are able to make out expected pco2 here is 19.85 and the pco2 which we are seeing here is 15.8 yes dr anjani all right it's metabolic acidosis the only thing is yes so we are trying to see whether there is a respiratory compensation which has started so yes it has started because the pco2 in the abg is lesser than the expected pco2 so dr neha let's go through this if the pc if the patient's pco2 is within the predicted range there is no respiratory if the pco2 is greater this indicates respiratory acidosis if the pco2 is less than expected so here we are seeing the pco2 which is less than expected the calculated value comes to 19.8 but the pco2 in this avg is 15.8 so if it is less than expected as you can see if it is less than expected there is an additional alkalosis occurring so there is a compensation which has started for this blood gas yes dr stravan is correct it is showing compensation which has started but the abg is showing a significantly bad ph means this patient survival is at stake unless you correct the metabolic acidosis very fast and for that you need to know what kind of acidosis is it is it a normal anion gap or a high anion gap metabolic acidosis because you will have to take a call about treatment accordingly for example in diabetic ketoacidosis though the acid levels are high it would not be to give bicarbonates it would be rather to control the blood sugar by giving the infusion of insulin why because the pathogenesis is insulin the problem is there's insulin lack of insulin there is gluconeogenesis there's glucogenolysis and that is precipitating the formation of acids so if you just start correcting the acidosis that will not help you need to correct the infusion of you need to give the insulin infusion and maintain the sugars so that the acidosis is correct okay i think what he is saying is that it's mentioned in kilo pascal's okay okay okay okay what we did not see was it mentioned in kilo i'm sorry i'm sorry for that someone brought it to my notice what is mentioned is that the pco2 was in kilopascal so even i made a mistake here by rushing through the pco2 but it is in kilopascals and the normal range is mentioned there is 4.5 to 6.10 so it's actually going higher so the calculation has to be in kilo pascals so co2 here as mentioned is high i agree with that so we go to one more clinical scenario now let's put it in our mmhg that so that we can stop the confusion in that a 26 year old mechanic is brought in by an ambulance apparent overdose of an unknown substance and on arrival his vital signs are is hypotensive his saturation is maintained on the room air so just check the saturation is maintained on room air that means the lungs are doing well is tachypnic respiratory is very high so the lungs are normal the saturation is good but the respiratory rate is very high and what do we see the ph is 7.15 the po2 is 115 the pco2 is 20 okay the pco2 is 20. now what is happening in this blood gas i think here you can apply it in a better way the vectors formula because here it's all in mmhg so no confusion will happen with the calculation so if you this is of course going in favor of a metabolic acidosis because the bicarbs are low so how do we interpret this abg so if you interpret this avg i want to know a few things one is it metabolic acidosis is it uncompensated if it's partially compensated is it fully comprehensible what is the av so doctor pram is answering correctly metabolic acidosis but is it uncompensated should we call it an uncompensated metabolic acidosis so it is uncompensated naturally we are going to say uncompensated because the ph is not yet in the normal range it's uncompensated if you apply the winter's formula you'll know the know it better try to check these abgs again when you see a rewind of this particular session so that you can apply it in a better form uh one more thing which comes added one was the winter's formula we said then we talked about the anion gap we talked about the correction for albumin one more factor which comes here is the delta gap now if you read this slide then you will find that delta gap is actually a interpretation of the anion gap only but it's a simplified equation which does not require a bicarbonate value at all it just needs a sodium minus chloride minus 36 so that's the simplest way by which we can calculate the type of acidosis so interpretation of the ratio is also mentioned here if the ratio is minus 6 or still lesser that is minus in negative it would be in a mixed high-end normal anion gap acidosis it will be a high as well as normal if it is between minus six to six it's only a high anion gap acidosis and if it is over six it's a mixed high anion gap and metabolic alkalosis so we can actually find a delta gap also to help us know what is the compensation or occurring or not whether it's a high an ion gap or a low and [Music] so you can take help of this formula as well because that doesn't put into addition about the into the calculation of the potassium or even for that the bicarb it is sodium minus chloride minus 36 that is the formula yes dr neha you were right it's the same as the winter's calculation the earlier abg so it's showing no compensation which has happened so i will not go into this it will be confusing further lactic acidosis i think we have discussed earlier the causes of lactic acidosis there are types so we will just discuss the therapeutics and what is the important few of the last couple of slides then we can take some questions also if time permits but this is important because sodium bicarbonate should probably not administer to patients with diabetic acidosis ketoacidosis is a strong agreement on the on the consensus statement for the treatment of diabetic ketoacidosis and in case of salicylate poisoning these are specific scenarios of metabolic acidosis its administration of bicarb in the therapeutic management of salicylic acid poisoning is very very very important is life saving whatever is the ph value and should renal replacement therapy be used in severe metabolic acidosis and if so in which ones so in case of shock and acute renal suff insufficiency the expert suggests initiation of the renal replacement therapy if the ph is below or equal to 7.15 in the absence of severe respiratory acidosis and despite appropriate treatments see these confusions come up when you see a blood gas suddenly of a patient and ph is 7.24 and then in ph of 7.24 you need to know the bicarbonates you need to know the creatinine and you need to know the blood pressure so many aspects are to be considered when we come to the therapeutics of a patient okay so sodium bicarb avoidable in a patient with decay diabetic ketosis try to treat you should be treating with an insulin infusion good amount of hydration in cases of acute salicylic acid poisoning the best way is to give bicarbonates and in cases of when should we use a renal replacement therapy i have already mentioned there as the causes okay as the indications similar there are certain things like uh methanol or ethylene glycol poisoning and the renal replacement therapy if the anion gap is above 20 or if there is renal insufficiency or visual impairment so you see that it's when you are going into critical care and when you are actually planning therapy you need to find dynamic there are certain indications even on crrt where we are giving renal replacement also we need to find the high end and the gap and how much is it if there is renal insufficiency so even for that matter certain ventilatory settings may be changed so if if there is a acidemia so the expert suggests that compensating for acidemia by increasing the respiratory frequency without inducing intrinsic positive and expiratory pressure that is peep so there are certain things which will come up when we think about uh sort of you know the management of this based on the blood gases want to take screenshot of abg slides question which questions are you talking about you may actually see these slides later on when you you know go through them now just coming to the last couple of slides before we stop is about putting all this formulae into one block okay all right to just make it a little easier and clearer for those who are with me even right now is always remember ph is very important there are different formulae to be applied we have discussed the formulae for acute acidosis chronic acidosis acute alkalosis chronic alkalosis we have discussed the formulae for metabolic acidosis and when we see lactic acidosis what should be done what are the causes of normal anion gap iron and gap acidosis also we have seen and we have also understood what is the delta gap so if you keep this q formulae in your small book in your handbook you can apply them to the blood gases you see and then for yourself with the clinical scenario you can match them i always feel that when you see these abg's it all comes to be important when you have a patient who is technique who is sweating and who is having a female pulse and we see certain changes in the carbon dioxide it all will be applied and then the treatment will start so again there are there are easier ways to handle it so this last one that's last but one slide is about uh the metabolic acidosis compensation formulas but for all those who are you know going to be interpreting these abgs in the days to come try to make your own small small understanding don't you can't mug up all the formulas at a time so you'll be specific for one metabolic acidosis winter's formula respiratory acidosis how much should be the change which is happening so this is a very important slide for me because the third point where we say that for respiratory acidosis for every 10 increase in the pco2 the ph decreases by 0.08 in acute respiratory oscillosis and point zero three in chronic respiratory acidosis this will help you to know whether there is a metabolic compensation happening or no so respiratory acidosis has a specific formula which you should know for every 10 mmhg increase in the pco2 in acute and for 0.08 will be the decrease in the ph and 0.03 in chronic respiratory acidosis so with that i think we'll take some questions because last time also there were many questions to you know which were asked by by the people who are listening so if you have any questions and i will just stop at this last slide which is actually summarizing the oxygen hemoglobin dissociation curve so this this this forms i think all of those who have passed medical school medical college they have gone through this diagram which was mentioned in the physiology books of guidance okay try to remember this but this when we see there is a drastic fall of the po2 when the saturation drops below 90 so there is a curve which is seen which is called as the oxygen hemoglobin dissociation curve and you can see the saturation and the po2 in the graph format so at 90 saturation the po2 is 60 and that's why we take it as a golden figure or golden number that saturation should be about 90 moment saturation goes below 90 there is a sudden drop of the po2 from 60 to 40 to 20 so that's the reason why we should be concerned about land then there are reasons where there is a shift and dissociation of oxygen occurs from the hemoglobin so there are reasons for that but i think you can go through this graph whenever you time permits for you but meanwhile go through the formulae for the abg's interpret as many abg's as possible if you have any doubts you can always ask us for i mean you can come back to us through netflix and we can try to solve your problems thank you so much sir uh i can see a lot of amazing comments please have this lecture again dr ashwin is saying uh dr ashwin you can go to replay section watch it again and i'll say it if you have any doubts you can definitely write us on support mail or you can connect to us via intercom whatsapp feel free to ask your doubts uh wonderful session sir i'm sure it's it must be a long day for you uh taking session at 9 30 today but thank you all all of these all of you we should thank all the audience as well i'm sure they'll also have a long day they must be working at hospitals clinics studying so even lot of lot of appreciation for them also to be with us today very informative amazing question i can see a lot of appreciating comments up so doctor and who she's asking if you could uh repeat ventilator setting section i had put up that slide i had brought it to that slide so dr anki be saying that can we predict uh so2 from ea yes absolutely so it would be the same but i i don't think that is much needed i mean if you are doing a abg and you are getting a pao2 you are going to know the saturation anyways from that i think the how to infuse sodium bicarbonate uh it should it be diluted or given directly and how to so so last thing also i had mentioned that so see there are various schools of thoughts let me tell you that there is no strong recommendation that this is the only way but uh the calculation once it happens we tend to we should be using say fifty percent of the calculated bicarb as a bolus and then 50 of it to be given over an infusion and naturally you will be repeating a blood gas again after eight to 12 hours to see what is the status of the acidosis at that point of time right thank you sir uh dr ankur she's saying so are there any contraindications to ventilator correction and what are the side effects contraindications to uh ventilator setting that you uh ventilate a correction uh that you mentioned actually see primarily ventilator settings are not done for correction of acidosis and alkalosis ventilation changes are done to correct the hypoxia and the pco2 so when you are correcting the acidosis you will take help of the metabolic parameters having said that if there is a alkalosis which we want to induce in a patient with metabolic acidosis we are going to give increase the respiratory rate we are going to keep the saturation maintained and you will have to monitor the carbon dioxide levels if you have an etco2 that is the end tidal carbon dioxide monitor so that should be enough to help you out thank you sir uh dr narayan is asking abc will show and pulse oximeter will show sao2 is that right abg will show the saturation and the pao2 both other than that we have covered all the questions so uh dr raj karen has put in metabolic acidosis below which ph should we start replacing bicarbonate below 7.2 would be a better or better way to start treating the bicarbonates of course not forgetting to treat the underlying cause the last time also there were a lot of questions on correction and you have uh covered with each and every case so uh to everyone i would request if you want to brush up everything again you can go to replay section so i guess with this uh we can wrap up and i'll definitely get back to you if there are any questions uh so i'll just give one moment to them because again a lot of things are boring i think we'll keep a question in question questions itself yeah uh so can we comment on ebg if it is arterial or venous by just looking at the report so i think in the first session we first talk on abg's we did mention the differences in the arterial arterial blood and the venous blood so there is not a major difference except from the po2 point of view because naturally we are seeing venus blood so i don't means it is not necessary to what happens is in the in practice when we see a blur sample sent and then we see that the po2 is low it is considered it is venus but remember abg's are predominantly done for measuring the ph and ph is not vastly different in arterial and venous blood so you did not repeat a blood gas just to make the ph you can get a rough idea from the sample and you can treat it accordingly but i think they should uh check our slides in the first session that may be a little more helpful so with this i would uh wind up the session now uh and if there are any questions i'll definitely get in touch with you and get it answered looking forward to many more such interesting in coming days thank you thank you bye


Interpreting an arterial blood gas (ABG) is a crucial skill for physicians, respiratory therapists, and other health care personnel. ABG interpretation is especially important in critically ill patients. It is an essential part of diagnosing and managing a patient’s oxygenation status and acid–base balance. In order to analyze blood gases, it is important to understand the associated physiology including the nature of acids and bases, and pH levels. Acid–base imbalances can cause complications in a variety of diseases, and the deviation can sometimes be so extreme that it becomes a life-threatening risk factor. The proper collection, management, and analysis of an ABG specimen are all critical to accurate results. Join us LIVE on Medflix as we comprehend the fundamentals of ABG Interpretation with Dr. Salil Bendre. This session is continuation of ABG interpreation part -1 and Dr. Salil will be covering clinical application and correction techniques.


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