need help with ABG question

  1. My teacher gave us a bunch of ABG practice questions. I did most of them but is one that I cannot figure out. Anybody have any input on this and the rationale for it? Thank you!!!!

    ph- 7.5
    PCO2- 50
    HCO3- 23
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  2. 12 Comments

  3. by   leslie :-D
    Quote from amyg22
    My teacher gave us a bunch of ABG practice questions. I did most of them but is one that I cannot figure out. Anybody have any input on this and the rationale for it? Thank you!!!!

    ph- 7.5
    PCO2- 50
    HCO3- 23
    i honestly don't think it can be determined.
    the pH clearly indicates uncompensated alkalosis.
    the c02 is acidotic.
    the hc03 is wnl...
    the pt probably has a mixed disorder.
    anyone else?

    leslie
    Last edit by leslie :-D on Oct 14, '07
  4. by   jmgrn65
    I havent' heard of the co2 being described as acidoitic or alkalosis, I have to do some research.
    my thought is respiratory alkalosis.
    now I am off to do some research.
  5. by   deeDawntee
    This is a very difficult one to determine without the clincal picture.
    But just a guess, would be a patient with severe COPD that is vented and has blown off enough CO2 to bring up the pH to an alkalotic level and the kidneys have not had the chance to compensate. I would bet the baseline CO2 is much higher. Thats the only scenario that makes sense to me....

    I love these befuddling problems!! Thanks for posting it!

    So yes, resp alkalosis but only with a baseline CO2 much higher with underlying COPD.
  6. by   eamon66
    At a guess think it represents a respiratory alkalosis with partial compensation. Although ph is still demonstrating an alkalosis (so only partially compensated), the Co2 is swaying towards the low end of average (alkalosis) whilst the body is attempting to compensate by shifting HCO3 which is leaning towards an acidosis. Then again could be talking complete and utter horse manure. Any other takers?
  7. by   jmgrn65
    according to this if you remember this table, so it would be metabolic alkalosis.
    well I tried to post the table, but it didn't turn out right.

    Leslie i understand what you mean know.
    http://rnceus.com/abgs/abgmethod.html#anchor1356388
    Last edit by jmgrn65 on Oct 14, '07 : Reason: did not show up the way it was intended.
  8. by   bigmona
    dee's explanation makes the most sense to me... the kidneys take 24-72 hours to compensate for an out of whack pH. so the only thing that makes sense is a COPD patient who lives with a CO2 in the 60's but becomes alkalotic with a lower CO2 in the 50's.
  9. by   leslie :-D
    Quote from eamon66
    At a guess think it represents a respiratory alkalosis with partial compensation. Although ph is still demonstrating an alkalosis (so only partially compensated), the Co2 is swaying towards the low end of average (alkalosis) whilst the body is attempting to compensate by shifting HCO3 which is leaning towards an acidosis. Then again could be talking complete and utter horse manure. Any other takers?
    - i don't see any compensation of the pH:
    it would have to be within the range of 7.35-7.45, wouldn't it?

    - co2 again, is outside normal range (35-45): 50 would be acidotic, and

    - hco3 (22-26) is closer to alkalotic range.

    i haven't read these in quite some time.
    but i used to whizz through them....yrs ago.

    leslie
  10. by   caldje
    If there is a high pH you have alkalosis.

    If the CO2 is high, you are reatining CO2 to try and compensate.

    If the HCO3 is normal, you don't have too much Bicarb. there is another metabolic cause for the alkalosis. There is only one other option from here...... too little acid.

    Vomiting, medications, hypokalemia causes H shift... etc.

    good luck!

    p.s. not to say that a chronic resp acidosis with a sudden hyperventilation isnt possible.

    p.p.s- on second though the chronic resp acidosis isn't possible, i dont think, because at that pCO2 you would expect the bicarb to be 28. a sudden drop in ventilation, that could cause the higher pH, would likely not yet effect the HCO3, which is lower than the expected calculated value for a chronic respiratory acidosis.

    you really need a clinical scenario and electrolytes. :-[ lol
    Last edit by caldje on Oct 14, '07
  11. by   eamon66
    I think the difference between fully and partially compensated is that the pH is not corrected in partial. As for the co2....i just figured out that you's must use mmHg in the US. We use kpa in the UK so oops. Guess that blows my theory!
  12. by   leslie :-D
    ok, i found the correct answer, thanks to jmgrn65.

    follow this link: www.rnceus.com/abgs/abgexamples.html
    scroll to example #5

    partially compensated metabolic alkalosis.

    elevated pH = alkalosis

    elevated co2 and elevated pH = metabolic cause of alkalosis. resp acid is compensating for increased pH.

    thank you, jmgrn!

    leslie
  13. by   Patient_Care_Asst
    ph- 7.5
    PCO2- 50
    HCO3- 23i honestly don't think it can be determined.

    the pH clearly indicates uncompensated alkalosis.
    the c02 is acidotic.
    the hc03 is wnl...
    the pt probably has a mixed disorder.
    anyone else?

    ---------

    Agreed this ABG stab result is exhibiting a classic example of acidosis/alkolosis.

    My Best.
  14. by   PageRespiratory!
    Hello everyone,
    I think I can give a little insight here. pH of 7.5, alkalosis, period. pCO2 of 50mmHg, hypoventilation, period. Don't forget, the HCO3 from a blood gas analysis is calculated, NOT measured! This is an example of an analytical error of some sort. A respiratory acidosis as compensation for metabolic alkalosis is non existent. Although these values would suggest that. CO2 is THE ONLY measurement of ventilation.(not resp. rate ) There is an inverse relationship between arterial CO2 tension, and pH, in other words, the more CO2 the more acidotic. Obviously the renal system can partially or fully compensate for chronic hypercapnea. (resp. acidosis)
    Last edit by PageRespiratory! on Oct 15, '07

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