please help with these ABG's

[emmycRN]

82yo male on bipap FIO2 90% with diagnosis of pneumonia. o2 sats WNL.

ph 7.54

pco2 51

p02 64

hco3 43.6

BE 18.5

I am a relatively new ICU nurse and ABG's aren't my strong point. Charge RN and RT said ABG results were respiratory alkalosis due to anxiety and pt fighting bipap. If this is correct why is bicarb so elevated. What is your interpretation of these results?

[loafin']

I am a brand new nurse in ICU and I am trying to get a better grip on ABGs. Your explanation is interesting and I want to make sure I understand it.

Is this something you would see with COPD patients? (That's the first condition that comes to mind where someone is chronically hypercapnic).

What your saying is that this is definitely a respiratory problem because the pt is used to having a co2 level much higher than what is on the ABG results...(a condition of chronic compensated respiratory acidosis maybe ???). However, when they become anxious and hyperventilate, blowing off more of their co2, it sends them into respiratory alkalosis... even though the CO2 is still at an acidic level and the bicarb is at an alkalotic level. And the low potassium was actually due to the pt hyperventilating and excreting H+ ions.

Am I understanding you correctly?

I still don't understand why the bicarb is so high? I assumed the bicarb would be acidotic to correct respiratory alkalosis. However, considering the CO2 is acidotic, I don't know if that would make a difference. Or is the bicarb high simply as a result of the hypokalemia?

You understand exactly. There is a formula called winter's formula for expected pco2 with a given hco3. The abg and client on bipap is a big clue

Remember HCO3 compensates slower than co2. And actually the bicarb might be slightly lower than client's normal, difficult to know exactly without seeing a normal baseline abg for this client. I wonder if this client had a previous admission with another abg.

Give yourself more credit, sounds like you have a pretty good grasp. Sometimes we have to think out of the box and not automatically assume that everything we learned in nursing school is law. I mean we know our normal ranges for our lab values, but sometimes when things fall out of range especially abg's, it's not always as simple as using the arrow system(when co2 is up and hco3 is down, it is this...).

[loafin']

How TXnursingstudent explains it is how I learned it. If what you explained is more advanced then the basics that I learned then enlighten me some more.

BabyMO1,

PM me if my reply to asoldierswife05 still did not explain enough.

[olllllllo]

3 pages of explanation on this guy's ABG and nobody has even mentioned an AG or delta? Accurate interpretation of an ABG and pt acid/base status requires utilization of the same steps everytime, regardless of how much the hx may lead you to to think one thing or another. Who is to say this pt may not have an underlying gap acidosis, etc?

[n2b8ter]

the abg is metabolic alkalosis. the co2 drives the ph in the opposite direction. if it is elevated then the ph is low. if it is low, then the ph is high. that is how you can determine that it is respiratory cause. you see here the co2 is elevated and so is the ph. so, it cant be respiratory. so it has to be metabolic. and we see it is because with metabolic causes, the bicarb and the ph will change in the same direction. as we see with this abg, the bicarb is elevated and the ph is also elevated. so, since it is going in the same direction, the cause is metabolic. this website link explains abg's and even has a calculator that will tell u what the abg is when you put in the results. www.anisman.com

the lungs are trying to raise the co2 so the ph will go back down to 7.45

here are some things that can cause metabolic alkalosis:

in reference to website: http://www.tjc.edu/nursing/PatriciaCryer/blood_gases.htm

LOSS OF HYDROGEN IONS THRU VOMITING, NG TUBES

INCREASED INTAKE OF BICARB

LOSS OF POTASSIUM FROM FISTUALS OR DIARRHEA

IV BICARB, DIURETIC THERAPY

MINERALOCORTICOIDS

you have to treat the cause and monitor for adequate renal function.

poor guy - he had to deal with pneumonia on top of everything else. hope this helps.

[Soonstudent]

Actually this is quite simple. I've seen it hundreds of times with chronic hypercapnic's who are very anxious(especially fighting Bipap). You will see the same thing with a client who is a chronic hypercapnic who is place on vent with too high rate. This client's co2 is below his normal. His normal is somewhere around 73 mmhg +or - 2. So it is actually respiratory alkalosis. There is no strange electrolyte imbalance or a drug that caused it. PM me if you would like a more detailed explanation.

I realize this is an old thread but this is a question I had last weekend. I had a pt with the same numbers, however it was compensated metabolic alkalosis. The pt was on a trach collar when we drew this gas. When we put the pt back on the vent for rest, we grossly overvetillated, bringing the PCo2 down to normal, which allowed the PH to rise to 7.63 because the bicard was high. The bicard was up due to lasix which causes you to spill K+ and H+ ions. The dillution effect also causes a trasient rise in bicarb because it is more concentrated. It would help to know the anion gap. I also see how a Co2 retainers bicarb would be high to compensate for the excess H+, but how do you tell the difference?

[burn out]

The ph, pco2 and po2 are classic of someone with copd esp with normal sat. The elevated hco3 level from metabolic compensation for the elevated co2 reflexed in the ph. The climbing bun creat are from the lasix drip, is there CHF and wouldn't demadex be kinder if a diuretic is even needed at all. Usually pnemonia gets fluids .

[phiposurde]

afterb reading the post i remember a presentation i went on abg. here what it was said:

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n

hco3 + 15 = pco2 +/- 2

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n

if it does, appropriate compensation has occurred

and there

is no secondary process

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n

if it doesn't, another primary process is at work

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n

if co2 too low = respiratory alkalosis

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n

if co2 too high = respiratory acidosis "

unfortunetly i was not available to find more detail info on where it come from. in this case against evryone one belief, it is resp. akalosis. but maybe everyone is wright( i am a people pleaser lol). sometime there one then one process that can happen at once. the kidney portion seem like an decent option!! would require more information ( blood result and story) so that we can tell about that debate!:monkeydance:

[SanFranSRNA]

How about giving this PT some Diamox to get rid of the base. Hopefully we can achieved the diuretic effect plus getting rid of excess base.

[phiposurde]

Unfortunetly I was not available to find more detail info on where it come from. In this case against evryone one belief, it is resp. akalosis. But maybe everyone is wright( i am a people pleaser LOL). Sometime there one then one process that can happen at once. The kidney portion seem like an decent option!! Would require more information ( blood result and story) so that we can tell about that debate!:monkeydance:

After thinking about it, and reading more. I would say there a double alkalosis. The ph, if it would be only chronic, should be in the normal range which it's not.The low potassium could be explain by the chronic state, but let say the diuretic get the hypokalemia worse. The kidney would response by increasing H+ secreation and HCO3- retention. Also, H+ would have a free pass to enter into the cell. I would say to replenish in potassium to fool the kidney and let the patient get back into homeotasis at her own pace. Especially if she is a chronic woudn't want to paly to much.

[mrmike]

To me it always seems like people make ABG's a little more complicated then they need to be. >7.40 = alk cause of alk = low co2 (resp)or high bicarb(met). Your senario is high bicarb so it is metabolic alkolosis with respiratory compensation. Be leary of advice on here sometimes. 2 people said met acidosis. >7.40 = alk,

[phiposurde]

To me it always seems like people make ABG's a little more complicated then they need to be. >7.40 = alk cause of alk = low co2 (resp)or high bicarb(met). Your senario is high bicarb so it is metabolic alkolosis with respiratory compensation. Be leary of advice on here sometimes. 2 people said met acidosis. >7.40 = alk,

***I would have to disagree with your point that ABG are that easy. I believe in our nursing training they don't teach us enough. When you start to read in medicine book there more to it then just some up and down. I went to many talk on ABG and they keep saying the ame old stuff. They never teach us how to make a bigger picture of a simple piece of puzzle. One of my mentor told me once the best piece of advice there was always ask yourself " what else could it be?". In this case, sure the CO2 and HCO3 are high, but the PO2 and the So2 is low, so wich mean probably a chronic state. So we have to think differently and applied different formula cause the "normal" doesn't applied. anyway just my 2 cents!

[meandragonbrett]

We aren't taught a lot of things in depth in nursing school. That is not the obejective of nursing school. The objective is to make us minimally competent to provide safe care. Any education that is more in depth is on our own shoulders.