ABG Interpretation: The Delta Ratio and Triple Disorders (Lesson 6)

How to use the delta ratio (a.k.a. the "delta-delta") and the delta gap to diagnose mixed metabolic disorders, including triple acid-base disorders

[@johndavis3299]

Thanks for the lectures!! Im an ICU RN in TX watching your lectures makes me understand why we r doing something rather than going through the motions. It makes me more confident in myself and safer patient care. Good stuff!!

[@ranasalman5259]

Dr Eric, it will be quite useful to see your perspective on ABG vs VBG for interpretation of acid base balance.

[@drarpitsaha9697]

I am a resident of icu ... ur lectures really help me...speciallly this one...thank u so much...now I am a fan of u...

[@n.e3345]

Thank you very much Dr. Strong. You always make me understand difficult concepts!

[@sunving]

Thank you Dr Strong, You lecture is clearer than the Washington Manual especially emphasize Delta Ration than Delta gap/ I thank you very much. This is my second round to watch this. If you have time just update Covid 19 situation in Stanford or VA then. Good luck.

[@StrongMed]

Thanks so much for all of your comments over the past several weeks! I hope you've been doing ok during these times. I'm hoping to post a COVID-related video in the next couple of days.

[@Nico_flies]

Best video like this that I have seen

[@StrongMed]

The discrepancy between ABG HCO3 and serum HCO3 is large enough to suggest the 2 tests were not done at the same time, which can potentially lead to erroneous conclusions about what's going on with the patient. Negative delta ratios can occur, and are very briefly mentioned in lecture 7. Neg delta ratio + low pH --> suggests mild elevated AG met acidosis + chronic severe resp. acidosis. Neg delta ratio + high pH can be seen in mix of elevated AG met acidosis + met alkalosis. Hope that helps!

[@ShadoOoni]

Good bless you, ill pray for you a lot. You save my life! my professor poorly explained this concept and poorly have written the the slideshow, but you made it easy! Thank you so much

[@gauravphogat9301]

eric sir you r the best...thanks for making dificult things so simple. sir can you please take a lecture on iv fluids in which condition which fluid is to be given....

[@xBassel92x]

That last example was vicious !

[@andreidaniacovache]

When a respiratory disorder is present and you are calculating the delta bicarb (such as in the last example, the triple disorder), is it ok to use 24 as the "normal" bicarb? In the example it seems strange that your calculated delta bicarb as 2mEq/L (24 - 22), it would seem more logical to me to calculate the expected bicarb (as you say in the video around 26 or 27) and subtract from that the measured bicarb of 22. Intuitively it makes more sense to calculate the deviation of bicarb from its expected value in the context. In this case this would give a delta ratio of about 2.5 (10/4) which gives the same overall diagnosis but seems closer to the values seen in other examples. Additionally, in a *hypothetical* extreme disorder with a CO2 of 75mmHg and HCO3 of 24 you would easily identify a respiratory acidosis as well as a metabolic acidosis, regardless of the anion gap. Then, calculating the delta HCO3 you would get... 24-24 = 0? I this example this algorithm would always result in diagnosing a metabolic alkalosis, regardless of the actual value of the anion gap. I know that the values in this example are made up and extreme, but this indicates that even in less extreme examples there would be a tendency towards overdiagnosing a triple disorder with metabolic alkalosis while underdiagnosing one with elevated AG acidosis with normal AG acidosis. I can also think of some more hypothetical scenarios, including small changes in the example provided in the video, where this algorithm seems to force you to diagnose a specific triple disorder regardless of the actual anion gap but I don't think it's very relevant. TLDR: is it correct to use 24mEq/L as the "normal" bicarb value when calculating the delta ratio, even if a respiratory disorder is present which would otherwise change your "expected" bicarb value for a patient?

[@shalini946]

Thanks for this series on ABG! you are amazing!

[@raveendirangopal1073]

Excellent lecture,Sir

[@StrongMed]

Low pH and high PCO2 diagnostic of a resp acidosis. If there was any compensation, HCO3 should be high. As it's actually lower than normal, a concurrent met acidosis is present, in this case an elevated AG acidosis. Delta ratio = [AG (measured or adjusted) - AG (normal)] / [HCO3 (normal) - HCO3 (measured)]. In this case, delta ratio = (32-12) / (24-10) = 1.4. No third disorder.

[@medicalblogger7388]

DR. Eric ,in your first example the delta ratio was 0.8 which implies the pathology is ketoacidosis but you said the pathology is lactic acidosis is the answer

[@sunving]

Thank you very much Dr Strong. I am kind of get it but I probably need to read or watch a couple time more.

[@teero16]

BRILLIANT! Thank you so much really 🙏🙏

[@shubhigopal9385]

Thank u so much sir for this awesome lecture

[@hebahussein9423]

Thank you. Very well done you're awesome.

[@kishen5959]

Hi, Dr. Eric. Thank you so much for these ABG lectures. Really appreciated. I have just one question: In the example 2, the delta ratio suggest of a concurrent metabolic alkalosis. Yes dr, I agree with u in terms arithmetically. But, how do you differentiate the increase in delta ratio is due to a concurrent metabolic alkalosis or due to low GFR secondary to dehydration in DKA? Thanks in advance! Appreciate if u could explain this.

[@StrongMed]

The expected range of the delta ratio, as shown at 5:35, isn't calculated, but rather based on imperfect empiric evidence as reported in the literature.

[@lehu8529]

2:20 I don't get how adding an acid disrupts charge balance.. an acid HA dissociates into A- and H+, right?

[@Dequiter]

Yeah. But *theoretically* the H+ is buffered by the bicarbonate

[@basel277]

crazy man, that was awesome! thank you!

[@biplabsharma5687]

In example 1, Delta AG + HCO3 = 8+14 = 22, which is in normal range. So couldn't the case be just elevated gap metabolic acidosis.

[@ldewolff]

Hello! Thanks for the amazing explanations. In your example #2, I understand that lactic acidosis explains the elevation of AG but what explains the normal gap metabolic acidosis? Thanks a lot!

[@sadmanjaoad6994]

Loss of HCO3 in diarrhoea gives normal AG acidosis

[@minnymoony]

I don't understand how you can determine that in example #1 the additional acid/base disturbance is a "normal gap met. acidosis", while in example #2&3 there is no mention of normal/elevated/decreased anion gap (I am referring to the Dx of step 5)

[@stephenbrandt165]

Hi Dr. Strong, I have gone through your chest x rays and ekg lectures and have learned so much from you, so thank you very much! I have a question on the triple acid base disturbance at the end of this lecture. You mentioned the alcohol use could have induced an aspiration-related lactic acidosis; I was wondering per your slide on oxidative phosphorylation inhibitors in a previous lecture if alcohol also would cause a lactic acidosis through that mechanism, or if this is not seen clinically. Also, you mentioned that it was a borderline call as to the assessment of if the HCO3 compensation was appropriate, and that the same conclusion would be reached in the end, I was wondering what you mean by that? Thank you!

[@konjunktiv2]

Brilliant!

[@ahlammohammed2135]

I wish you could be able to share the PowerPoint presentation with us !!!! :((((( I have been struggling to understand acid-base balance for years , so sad :(((

[@s.h.2935]

Hi, In your last example, wouldn't the "metabolic alkalosis" actually be secondary to the respiratory acidosis? If this is the case can we still talk about a primary metabolic alkalosis or should we call it a compensatory metabolic alkalosis? Thanks

[@mofralojan]

You are a Genius.

[@niveditamishra1]

in the last line of the triple acid-base example, how did u conclude on the third disturbance as an alkalosis?

[@34jitender]

Thank you very much

[@drskiro11]

when you say within the expected range @ 09:33 are you referring to those values you quoted for ketoacidosis and lactic acidosis i.e 1.6 and 1? If so how about in other cases of elevated gap acidosis, what is our reference with regards to what the expected delta ratio should be? Thank you.

[@ericstrong875]

Yes, I am referring to the expected range given the suspected underlying etiology of the elevated anion gap. Unfortunately, we don't actually know what the expected range should be in other forms of elevated gap acidosis (e.g. methanol and ethylene glycol poisoning). Most likely, the delta ratio for those other disorders should also be between 1 and 2, and I would guess that it's only ketoacidosis with intact renal function where the delta ratio range is lower (i.e. 0.8-1.2).

[@aishaoh91]

you are the best....thank you a lot

[@mys3lf4yu]

question: would't sodium need to be adjust for glucose in the example with Type 1 diabetic patient?

[@WhyNot-si4pj]

I believe so ! Adjusted sodium for glucose = Measured sodium + 1.6 (measured glucose/100 - 1) . The algorithm is a kind of approach that does NOT necessarily need to be that accurate !

[@jamalimurtaza6527]

Calculated AG is 20 while in delta ratio you have put 08 instead of 20 ?

[@StrongMed]

In the delta ratio calculation, it's the "delta anion gap" (i.e. the difference between the measured AG and the upper limit of normal for the AG) that is inputted into the equation. Measured AG of 20 minus the upper limit of normal of 12 equals the 8 that is shown on the screen.

[@mohamadaly]

Amazing

[@maryam-jk3mc]

I don’t get the triple disorders what the hell is this i feel like it’s a game like why there is three I’m lost.

[@NNCCCC63]

more volume please

[@eibonchua7037]

Sir, may i ask a question? I was wonder to calculate the expected range of delta ratio?

[@harsweth_]

👍

[@harsweth_]

In the first example...🔺AG + Hco3=8+14=22....which is 18-30 so high anionic gap metabolic acidosis????

[@p.1127]

Example 3 yaraladı

[@haithambatarseh866]

Am I the Only one who could not understand this topic perfectly? :(