Favorite Quotes
"For every complex problem, there is a solution that is simple, neat, and wrong." - HL Mencken
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"I hear and I forget. I see and I remember. I do and I understand." - Confucius
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"The good physician treats the disease; the great physician treats the patient who has the disease" - Sir William Osler
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" The best test of a person's character is how he or she treats those with less power." - Bob Sutton
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"Those are my principles, and if you don't like them - well, I have others." - Groucho Marx
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"The difference between genius and stupidity is that genius has its limits." - Albert Einstein
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"It is hard enough to remember my opinions, without also remembering my reasons for them" - Friedrich Nietzsche
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"Anyone can make the simple complicated. Creativity is making the complicated simple." - Charles Mingus
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"Not everything that can be counted counts, and not everything that counts can be counted." - Albert Einstein
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"A foolish consistency is the hobgoblin of little minds, adored by little statesman and philosophers and divines. With consistency a great soul has simply nothing to do." - Ralph Waldo Emerson
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"This ain't no party, this ain't no disco, this ain't no fooling around." - Talking Heads, Life During Wartime
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"What is hateful to you, do not do to your neighbour. This is the whole Torah; all the rest is commentary. Go and learn it." - Hillel, Talmud, Shabbath 31a
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"You will never understand bureaucracies until you understand that for bureaucrats procedure is everything and outcomes are nothing." - Thomas Sowell
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"An idealist is one who, on noticing that a rose smells better than a cabbage, concludes that it will also make better soup." - HL Mencken
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"If you only have a hammer, you tend to see every problem as a nail." - Abraham Maslow
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"A great teacher is one who realizes that he himself is also a student and whose goal is not to dictate the answers, but to stimulate his students creativity enough so that they go out and find the answers themselves." - Herbie Hancock
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"There are no facts, only interpretations." - Nietzsche
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"An education isn't how much you have committed to memory, or even how much you know. It's being able to differentiate between what you do know and what you don't." - Anatole France
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"In character, in manner, in style, in all things, the supreme excellence is simplicity." - Henry Wadsworth Longfellow ====
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ABG dilemma discussed
15 Nov2009
This is a classic ABG sequence:
| ABG | Admission (on 2 L O2) | Day 2 (Bipap 100%) |
|---|---|---|
| pH |
7.28 |
7.52 |
| pCO2 | 89 | 52 |
| pO2 | 60 | 373 |
| HCO3 | 42 | 42 |
Your tasks are to understand and explain the course of events for this woman having a COPD exacerbation.
1. What is the initial acid-base disorder?
The patient has a chronic respiratory acidosis with metabolic compensation. I cannot remember the calculations, so I found a calculator online.
2. What is the second day disorder?
This disorder goes by the name post-hypercapnic metabolic alkalosis. I sometimes use the phrase "revealed metabolic alkalosis". It occurred because the patient had an appropriate compensation for a chronic respiratory acidosis, and then we successfully improved ventilation – lowering the pCO2 faster than the kidneys can adjust.
3. What would you do now?
We gave the patient acetazolamide to lower the HCO3 . Here are the subsequent ABGs:
| ABG | Day 3 | 5 hrs later | Day 4 |
|---|---|---|---|
| pH | 7.63 |
7.41 |
7.36 |
| pCO2 | 40 | 59 | 62 |
| pO2 | 56 | 83 | 74 |
| HCO3 | 42 | 37 | 35 |
We give the acetazolamide to add stimulation to ventilation.
Related posts:
- My answer to intubated
- My thoughts on March 8 acid-base
- Another hyperkalemia – my explanation
- 15 days at the VA – day 3
- 17 days at the VA – day 12
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1 Response to ABG dilemma discussed
cory
November 16th, 2009 at 9:33 am
The disorder the second day techincally is a post hypercapneic metabolic alkalosis. This is common in patients with chronic CO2 retention that are ventilated to a normal level.
But in practice this is essentially a relative (not absolute) respiratory alkalosis in the sense these people have reset their CO2s usually around 60. When you provide more ventilation than that to them, you are essentially breathing them into an alkalosis that is not normal for them and that they won't tolerate because they will ultimately reset back to 60.
Attempting to stimulate their ventilation with Diamox is a reasonable approach, but it rarely allows them to reset to a normal pCO2 and a normal pH. The underlying compensatory metabolic alkalosis is a stimulus to hypoventilation that works at cross purposes to the Diamox.
I think the best approach in this patient is to stabilize from a cardiac standpoint, investigate any reversible pulmonary component (upper airway obstruction, bronchospasm) and titrate the oxygen appropriately.
These patients can be stable for many years with pCO2s between 50 and 60 and relatively normal pHs.
My general rule, one that I am happy to discuss because it is unsettled, is to avoid correcting respiratory acid/base problems with metabolic means and vice -versa. Stabilize the primary problem and let the body fix the ph problem.