No such thing as lactic acidosis?

[VanDiemen]

I know that this a controversial topic among biochemists, but how do you guys feel about the concept of lactic acidosis? Looking at any textbook shows that the lactate dehydrogenase reaction actually INCREASES pH by consuming a proton.

This review articles sums things up nicely: http://ajpregu.physiology.org/content/287/3/R502

How many of you still believe that excessive lactate production is a cause of acidosis, rather than an effect? I wanted to get an idea about what the current level of understanding is among anesthesia/ccm people.

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[vector2]

I didn't realize that there was a controversy here...my understanding is that in low perfusion states there is so much lactic acid production from anaerobic glycolysis that the liver gets overwhelmed and eventually plasma buffering systems get overwhelmed. Lactic acid itself has a ph of 2.4

 

[VanDiemen]

Yes that was my understanding before as well, however, when you actually go back and look at the reactions shown in any good text, you will see that lactate and not lactic acid is produced. The article I linked does a better job explaining it if it is still confusing. There is no proton to dissociate from lactate, and in fact, the reaction from pyruvate to lactate actually consumes a proton, helping to lessen acidosis. It is sort of like seeing a fire and then firetrucks coming and assuming that the firetrucks are causing the fire when in reality they are there to help.
Glycolysis itself creates two net protons that have to be consumed by the electron transport chain, and when oxidative phosphorylation is halted, then you end up with proton accumulation. In addition when myosin hydrolyzes ATP, it also releases one proton into solution, which is consumed when ADP is turned back into ATP in the mitochondria.

 

[Stank811]

I haven't had a chance to read your article you posted yet but like you said this is a good discussion with data to support both sides of the argument. What came first the chicken or the egg. Below is a good summary worth reading.

http://www.ccforum.com/content/18/5/503

 

[VanDiemen]

Thanks for the article!

 

[G-Man82]

I think the NEJM had a review of lactic acidosis not too long ago. It's worth reading to get a more complete picture on the subject.

 

[jdh71]

Yes that was my understanding before as well, however, when you actually go back and look at the reactions shown in any good text, you will see that lactate and not lactic acid is produced. The article I linked does a better job explaining it if it is still confusing. There is no proton to dissociate from lactate, and in fact, the reaction from pyruvate to lactate actually consumes a proton, helping to lessen acidosis. It is sort of like seeing a fire and then firetrucks coming and assuming that the firetrucks are causing the fire when in reality they are there to help.
Glycolysis itself creates two net protons that have to be consumed by the electron transport chain, and when oxidative phosphorylation is halted, then you end up with proton accumulation. In addition when myosin hydrolyzes ATP, it also releases one proton into solution, which is consumed when ADP is turned back into ATP in the mitochondria.

Once again strong ion theory comes to the rescue. Hydrogens swimming in a sea of salty body water?? Hehe. Of course it's the strong anion that causes the acidosis. It's the physical chemistry kiddos. H+ and Bicarb have nothing to do with it. Google: stewart strong ion. Enjoy.

 

[Morzh]

Once again strong ion theory comes to the rescue. Hydrogens swimming in a sea of salty body water?? Hehe. Of course it's the strong anion that causes the acidosis. It's the physical chemistry kiddos. H+ and Bicarb have nothing to do with it. Google: stewart strong ion. Enjoy.

My SICU anesthesia CCM attending was all over the stewart model. It was almost like a religion to him. Seemed interesting, I read a few articles. Some of it was over my head (lots of equations and chemistry stuff I'd forgotten from undergrad), but ultimately it makes sense. What I fail to see, and I'm sure it's 100% because I'm a relatively ignorant MS4, is how thinking with a Stewart model mindset actually changes management. It's cool and all, things are definitely less murky when you think of H+, CO2, bicarb as the dependent variables, but... does it change anything?

 

[deleted171991]

Google: stewart strong ion. Enjoy.

From the horse's mouth: http://issuu.com/acidbase/docs/htuab .

 

[polar403]

My SICU anesthesia CCM attending was all over the stewart model. It was almost like a religion to him. Seemed interesting, I read a few articles. Some of it was over my head (lots of equations and chemistry stuff I'd forgotten from undergrad), but ultimately it makes sense. What I fail to see, and I'm sure it's 100% because I'm a relatively ignorant MS4, is how thinking with a Stewart model mindset actually changes management. It's cool and all, things are definitely less murky when you think of H+, CO2, bicarb as the dependent variables, but... does it change anything?

It can, for example, help give an idea if the lactic acid is the main culprit of the acidosis or if it is just contributing.

 

[jdh71]

My SICU anesthesia CCM attending was all over the stewart model. It was almost like a religion to him. Seemed interesting, I read a few articles. Some of it was over my head (lots of equations and chemistry stuff I'd forgotten from undergrad), but ultimately it makes sense. What I fail to see, and I'm sure it's 100% because I'm a relatively ignorant MS4, is how thinking with a Stewart model mindset actually changes management. It's cool and all, things are definitely less murky when you think of H+, CO2, bicarb as the dependent variables, but... does it change anything?

It doesn't change management. At all. It simply gives you a better framework to wrap your mind around if you are the type that that likes that kind of thing. I know I am.

 

[Stank811]

JDH71. Do you every give bicarb? And if so in what situation? I have worked with docs that even if the Ph was 7.43 but there was a BD of -2 they would insist that bicarb should be given!

 

[Urzuz]

JDH71. Do you every give bicarb? And if so in what situation? I have worked with docs that even if the Ph was 7.43 but there was a BD of -2 they would insist that bicarb should be given!

They're idiots.

 

[G-Man82]

Ugh. No. It depends on what you're trying to correct. Don't ever correct a respiratory acidosis with bicarbonate. That goes without saying. If you're trying to correct a metabolic acidosis, then make sure you have room to increase minute ventilation; otherwise you'll get a paradoxical worsening of acidosis. I say paradoxical because you're intending to correct acidosis, but you end up creating more pco2 and actually add a respiratory acidosis on top.

Also, people have their various comforts, but in most cases I'll let the pH fall to 7.2 (maybe even 7.15) before trying to correct the numbers rather than the underlying cause.

 

[deleted171991]

Bicarb should be given only when bicarb was lost. Typically that's a non-anion gap metabolic acidosis with renal/digestive losses.

 

[Laryngophed]

Bicarb should be given only when bicarb was lost. Typically that's a non-anion gap metabolic acidosis with renal/digestive losses.

I think you could make the argument that it can be an adjunct in severe acidemia (while working to correct the actual problem, i.e. resuscitate) and/or with ECG changes.

But the indications seem to be far narrower than the reasons it is given in my very short experience.

 

[jdh71]

JDH71. Do you every give bicarb? And if so in what situation? I have worked with docs that even if the Ph was 7.43 but there was a BD of -2 they would insist that bicarb should be given!

I tend to give "bicarb" in a metabolic acidosis with single digit CO2 on the panel, especially if pH is less than 7.0. Sort of depends on the clinical situation though. Plenty of data that shows using a bicarb drip doesn't help or might even make things worse. So I use it more than a bit selectively and not as a reflex. Though according to strong ion theory it's not the bicarb that is making a difference it's the sodium!! Ha!

 

[jdh71]

Ugh. No. It depends on what you're trying to correct. Don't ever correct a respiratory acidosis with bicarbonate. That goes without saying. If you're trying to correct a metabolic acidosis, then make sure you have room to increase minute ventilation; otherwise you'll get a paradoxical worsening of acidosis. I say paradoxical because you're intending to correct acidosis, but you end up creating more pco2 and actually add a respiratory acidosis on top.

Also, people have their various comforts, but in most cases I'll let the pH fall to 7.2 (maybe even 7.15) before trying to correct the numbers rather than the underlying cause.

Sometimes in ZOMFG! asthma you will buffer a resp acidosis with sodium bicarb because your back is just that far against the wall. There's always THAM if the kidneys are working (which I've used once) or CRRT (which can take a bit of convincing if you need the renal guys to get it going for you). But severe resp acidosis like you see in ZOMFG! asthma really needs ECOR (or ECMO but it's a bit of overkill)

 

[G-Man82]

Sometimes in ZOMFG! asthma you will buffer a resp acidosis with sodium bicarb because your back is just that far against the wall. There's always THAM if the kidneys are working (which I've used once) or CRRT (which can take a bit of convincing if you need the renal guys to get it going for you). But severe resp acidosis like you see in ZOMFG! asthma really needs ECOR (or ECMO but it's a bit of overkill)

Agreed. I don't often see status asthmaticus, but I'm just waiting. The ventilator challenge sounds thrilling! I'm at an ECMO center, so if someone presents with ZOMFG! Asthma, and ECMO is next on the list of therapies, they automatically would get transferred to my unit. Here's hoping ...

And yeah it's probably the Na ;-)

I actually like THAM and use it occasionally for certain metabolic acidoses where I'm maximally ventilating and need more help with pH and renal is dragging their feet. I have to look up how to dose it again but I believe its base deficit x weight in kg = ml THAM needed. It's some good stuff.

 

[jdh71]

Agreed. I don't often see status asthmaticus, but I'm just waiting. The ventilator challenge sounds thrilling! I'm at an ECMO center, so if someone presents with ZOMFG! Asthma, and ECMO is next on the list of therapies, they automatically would get transferred to my unit. Here's hoping ...

And yeah it's probably the Na ;-)

I actually like THAM and use it occasionally for certain metabolic acidoses where I'm maximally ventilating and need more help with pH and renal is dragging their feet. I have to look up how to dose it again but I believe its base deficit x weight in kg = ml THAM needed. It's some good stuff.

http://www.ncbi.nlm.nih.gov/m/pubmed/26033128/

I had the chance to train under Leatherman. Best bedside critical care clinician I've ever had the privilege to learn from. Following his "rules" for mechanical ventilation in intubated asthmatics is like having a secret pirate map that gets you through the shallows, around the reefs, and past the angry natives to the buried treasure. Download the PDF at work. Email it to yourself or print it and pin it to a board somewhere. Dust it off when you need it.

 

[quickfeet]

Lactic acidosis actually doesn't exist. The emcrit acid-base episodes are also good to explain what jdh is saying about the Stewart physical chemistry method.

http://emcrit.org/podcasts/acid-base-i/