Cite this post as:
Scott Weingart, MD FCCM. Podcast 96 – Acid Base in the Critically Ill – Part V – Enough with the Bicarb Already. EMCrit Blog. Published on April 14, 2013. Accessed on January 26th 2022. Available at [https://emcrit.org/emcrit/enough-with-the-bicarb-already/ ].
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In Podcast 44 you say about Henderson-Hasselbalch: “I find this method to provide no comprehensive explanation for why things are as they are”. But you don’t shy from writing this very same equation on the current podcast as proof that bicarb can’t raise pH when minute ventilation stays the same… Go figure… I find this quote from Dorje (http://goo.gl/1QVja) interesting: “One of the interesting questions resulting from Stewart’s approach relates to how sodium bicarbonate corrects the metabolic acidosis. The metabolic acidosis may be corrected not so much by its bicarbonate content but by its sodium content. The increased sodium concentration… Read more »
Mathias, The equation is there because it was mentioned in one of the quotes. If you go by the Stewart approach this is a non-issue. I’m not sure where I used it as proof. The folks that follow Henderson-Hasselbach approach are the main progenitors of bicarb use as they argue, the patient’s bicarb is too low, so it makes sense to replete it. The equation demonstrates the futility of this. I’m not sure what the placement of the Dorje quote here is , that is exactly what was stated in the podcast. As to the bedside observation, it is easy:… Read more »
I totally agree that the benefit to the patient is at best debatable and totally unproven. My disagreement was about the net effect on pH and the need for the patient to vent off the ‘added’ CO2 that comes with bicarb. If you apply the Stewart approach, the argument that the patient must vent the additional CO2 is less of an issue. It’s always helpful to remind the advocates of the ‘bicarbonate does nothing good’ theory that they usually don’t think twice when they prescribe renal replacement therapy to a patient with renal failure and severe metabolic acidosis. The way… Read more »
Dialysis or RRT in general is a bit more complex as you are giving buffer base at the same time you are lowering anions.
Renal failure is usually a mixture of wide AG and normal AG acidosis. The latter is due to actual bicarb loss/depletion and will respond to bicarbonate.
The approach is simple:
With all biochemical abnormalities – always address the cause
For all metabolic acidoses = treat the cause rather than the pH
If normal AG you can give bicarb.
Hi Scott, in support of your discussion I just finished listening to EMRAP for this month. Please check out the segment on a recent TCA overdose in which the patient was intubated and received 20amps of NaBicarb IVP in the ED in rapid succession. Now in this situation of course the goal is to effectively compete with TCA molecules at the sodium channel receptors in the myocardium, but as an aside it was noted that the pH after 20amps only ended up slightly above 7.5 and this was with large minute ventilation to avoid acidemia from hypercapnea. I’m not sure… Read more »
I heard the same piece; kinda crazy.
Hi Scott thanks for the great podcasts A couple of comments: hyperchloraemic/renal acidosis and lactic acidosis are different conditions but you seemed to be lumping them together in the podcast. (This is from an ICU perspective, Not ED / acute resus) I would think its reasonable to approach the former at least with isotonic bicarb as one part of your maintenance fluid thus giving the sodium and volume while creating a more favorable strong ion difference, but without stressing the kidneys with excessive chloride to get rid of. This probably wont help in the lactic acidosis. Secondly the emphasis on… Read more »
OC, You may want to see the previous acid/base podcasts linked above to see that I am not lumping these together at all. This will be further emphasized in next week’s cast as well. Now as to the greater CO2 elimination with each breath as PaCO2 rises–that is very interesting. I’ve always thought of it as directly proportional to minute ventilation, but the fact that ETCO2 rises would indicate that more CO2 is being blown off. But as to how much extra and whether that amount is clinically relevant, that is a great question. I suppose you would need some… Read more »
Thanks Scott Apologies my name is Owen, in the middle of a night shift I defaulted to not putting my name on the web form.. Thanks for clarifying, I am looking forward to your future podcasts. I am not aware of any papers on the volume of CO2, its just been my understanding of it (ETCO2 X effective tidal volume (ie minus circuit and physiological dead space) seems a reasonable estimate of expired volume of CO2) but from a quick google search it looks like ventilator companies are going to start to use volumetric CO2 monitoring to sell their new… Read more »
yes, I agree with the logic. I’ll have to ponder the math.
Scott,
Think you have a typo at the top of this post: “When you can adjust PaCO2 to maintain a certain value (i.e. you increase minute ventilation), bicarb will lower pH as evidenced by this animal study (Crit Care Med 1996; 24:827-834). ” Shouldn’t this read “raise” pH?
Thanks as always for great free education.
great pick-up; now corrected
Dear Scott, I listened to your excellent discussion on acid-base treatment with Dr Kellum. I would like to provide an alternate opinion on many of your key points. Forsythe et al: Chest. 2000;117: 260-267. manuscript reviewed Hyperosmolar NaBicarbonate administrations in various populations of critical ill patients without a clear physicochemical endpoint (pH is not a physical-chemical endpoint) , prior to the development of early goal directed therapies, the importance of increasing O2 delivery/minimizing O2 consumption during the golden hours, early antibiotic administration, and adequate resuscitation endpoints were ignored. Many of the patients did not have any meaningful change in acid-base… Read more »
Ed, The subsequent podcast (Episode 97) discusses these very points and of course the only article I could link to for that podcast was yours. I think we have found one of the areas to discuss when you come on the show.
Look forward to it
Regards
Scott,
Is there a specific increase in minute ventilation that should be used in conjunction with sodium bicarbonate administration? Thank you for the podcast.
Regards,
Sandi
Just a bit more fodder for the “bicarb restraint” folks out there:
Kim, H. J., Son, Y. K., & An, W. S. (2013). Effect of Sodium Bicarbonate Administration on Mortality in Patients with Lactic Acidosis: A Retrospective Analysis. (J. I. F. Salluh, Ed.)PLoS ONE, 8(6), e65283. doi:10.1371/journal.pone.0065283.t004
Many limitations to this study, but keeps us wanting real prospective data for fluid resuscitation.
great find!
Hi Scott, My resident cohort and I have been arguing about the topic of this post for a bit now and we are split. Part of it seems to be that a number of us have given bicarb to patients with fixed minute ventilation and seen a significant increase in pH (though of course this may be due to confounding factors). The argument raised is based on the following: Titrations are a routine part of chemistry. Imagine you have a solution of acetic acid, that you are titrating with acetate. In this closed, aqueous solution, addition of acetate will bind… Read more »
Hi Scott-
Thanks for the great posts. If my lab doesn’t provide a BE, I guess I am unable to use this method and would resort to my anion-gap calculations as historically taught?