acid base balance help

Nursing Students General Students

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it's confusing and frustrating, but i have a feeling it's important.

is there anyway to simplify metabolic/respiratory acidosis and alkalosis, electrolyte imbalance etc? it seems like a foreign language to me right now. why must this be so complicated?

Think of rome

respiratory opposite

metabolic equal

our teacher told us that it helps

whether acidosis or alkalosis it goes for both when you know the normals

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its the compensated/decompensated part I don't get....

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I love it. Nursing needs more stuff like that. Science attracts me, lol. I noticed our book failed to mention this if I can type it out on here in a way that will make sense....

CO2 + H20 H2CO3 HCO3 + H

That's the formula: carbon dioxide and water yield carbonic acid which can dissociate back into carbon dioxide and water. Hydrogen and bicarbonate yield and carbonic acide which can dissociate back into bicarb and hydrogen.

What do you need help with to simplify it?

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Specializes in CNA.
R=respiratory

O=opposite

M=metabolic

E=equal

If the one value is up, and the other is down, then it's resp. If both are going in the same direction, then it's metabolic.

I still get confused on the compensation part.

Hope this helps.

Please learn this acronym last - after you learn the basics - not first. If it is all you understand you are sunk on the tests we had.

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Holy 8-year bump, Batman! The ROME acronym only works if you think of pH, PaCO2, and serum HCO3- on VERTICAL SCALES.

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I love it. Nursing needs more stuff like that. Science attracts me, lol. I noticed our book failed to mention this if I can type it out on here in a way that will make sense....

CO2 + H20 H2CO3 HCO3 + H

That's the formula: carbon dioxide and water yield carbonic acid which can dissociate back into carbon dioxide and water. Hydrogen and bicarbonate yield and carbonic acide which can dissociate back into bicarb and hydrogen.

What do you need help with to simplify it?

I'd add that it's important to understand that the HCO3 + H on the right of the above equation are actually ionized (HCO3- and H+) in aqueous solution. And to understand the polar nature of water, and how H3O+ and OH- are at equilibrium with H20 at a pH of 7. The chemistry of it is the easy part to me- it's the nursing implications of the various acid-base imbalances that's still a little overwhelming as I begin to prepare for when we cover this in the upcoming term.

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Specializes in Emergency Dept. Trauma. Pediatrics.

The ROME acronym is great if you are only giving ABG's and have to pick which one it is. For a lot of our questions on our tests we are given the values and need to say if it is Resp. Metabolic, and Acidosis or Alkolosis. For that, the ROME is quick and it works. (I should say a lot of our questions from the earlier med/surg classes, now in 4th semester we have gone big into compensation and stuff which gets more in depth.

I struggled with F&E the first time I had it, but for the advanced Med/Surg class I read the book Fluid and Electrolytes made incredibly easy and everything came together and made sense. I did well on the tests, the only thing I messed up on was the book I read said compensations can start after 6 hrs and I went off of that for one of our test questions but apparently in our book it says min. of 24 hrs and more likely days.

But the book really helped all of it make sense, not just Acid/Base but the electrolytes as well.

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Specializes in ER, progressive care.

Two books that helped me:

Fluids & Electrolytes Made Incredibly Easy!

Reviews & Rationales Fluids & Electrolytes and Acid-Base Balance by Pearson Prentice Hall.

But what helped the most was going over ABG's in my NCLEX class.

First you need to learn the normal values of pH, PCO2, HCO3- and PO2.

pH = 7.35-7.45

PCO2 = 35-45mmHg

HCO3- = 22-26mEq/L

PO2 = 80-100mmHg (this one doesn't really matter as much when trying to interpret ABG's but you should still know the normal value).

SaO2 = 95-100% (same with this).

Second, think of ROME: Respiratory Opposite, Metabolic Equal.

In respiratory acidosis, the pH is down (45mmHg). In respiratory alkalosis, the pH is up (>7.45) and the PCO2 is down (

In metabolic acidosis, both the pH and HCO3- are down (7.45, >26mEq/L). Notice how the pH and HCO3- are increased or decreased together, which is why metabolic is equal.

To interpret, look at the pH. Is it 7.45 = alkalosis, or does it fall within the normal range of 7.35-7.45, indicating compensation? (if the pH does not fall within the normal range, then it is uncompensated).

Look at the PCO2. Does it fall on the acidotic (>45) or alkaline (26) side?

Look to see which value matches the pH. Remember ROME!

Here are some examples:

pH: 7.21 = uncompensated (because it does not fall within the normal 7.35-7.45 range!), acidotic

PCO2: 32 = alkalotic (

HCO3: 14 = acidotic (

this is uncompensated metabolic acidosis. it is metabolic because the pH is low and the HCO3 is low (again, remember ROME!)

pH: 7.18 = uncompensated (because it does not fall within the normal 7.35-7.45 range!), acidotic

PCO2: 68 = acidotic (>45)

HCO3: 29 = alkalotic (22-26)

this is uncompensated respiratory acidosis, because the pH is low and the PCO2 matches it (ROME...it's opposite!)

pH: 7.36 = compensated because this pH falls within the normal range of 7.35-7.45. Even though it falls within the range, it is on the lower, or acidotic, side. so here we have an acidosis problem.

PCO2: 54 = acidotic (>45)

HCO3: 32 = alkalotic (>26).

look at what matches the pH...always think ROME...respiratory matches the pH, therefore you have compensated respiratory acidosis.

You can also have mixed problems.

pH: 7.52 = uncompensated, alkalotic.

PCO2: 36 = alkalotic

HCO3: 34 = alkalotic

uncompensated mixed alkalosis.

pH: 7.02 = uncompensated, acidotic (geez this pH is low! :eek:)

PCO2: 60 = acidotic

HCO3: 12 = acidotic

uncompensated mixed acidosis.

Uncompensated Compensated Uncompensated

pH Acid Alkaline

CO2 Alkaline Acid...Respiratory

HCO3 Acid Alkaline...Metabolic

Hope this clears up some confusion! ABG's can be frustrating at first!

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Specializes in Mother Baby RN.
You do have to understand the whys behind ABGs, and it does take a while to click, but a little cheat sheet until you feel comfortable:

RESPIRATORY ACIDOSIS:

pH is down

PCO2 is up

METABOLIC ACIDOSIS:

pH is down

HCO3 is down

RESPIRATORY ALKALOSIS:

pH is up

PCO2 is down

METABOLIC ALKALOSIS:

pH is up

HCO3 is up

(just kind of a quick check to see if you're coming to the right conclusion with your numbers)

Don't forget the compensatory mechanisms that can make a big difference.

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its the compensatory mechanism I was asking about.....

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its the compensatory mechanism I was asking about.....

The lungs or kidneys will try to move the altered pH back toward 7.4 to compensate for alterations caused by the other system. For example, with high pH and high HCO3- (metabolic alkalosis), the respirations would slow in an effort to retain CO2 to bring the serum pH closer to 7.4. If the pH moves back into the 7.35-7.45 range, it's referred to as fully compensated. If the pH doesn't get to within the normal range, it's called partial compensation. Respiratory compensation begins quickly but a patient can't stay in hyper- or hypoventilation for too long without dire consequences. Renal compensation acts more slowly, but is more effective and more sustainable.

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Specializes in NCT- rehab, BSN student.

My patho teacher recently told me to remember this acronym: ROME

it basically stands for Respiratory= opposite, Metabolic= equal

-So basically CO2 levels would be going in the opposite direction as pH if it was respiratory. The kidneys are compensating if there is an abnormal bicarbonate level.

-With metabolic bicarbonate levels would be going in the same direction as pH if it was metabolic. However, if the lungs are not compensating there would be no change in the CO2 levels but a change in bicarbonate ion.

-Something is fully compensated if pH levels are back to normal, if kidneys/lungs are compensating it is partially compensated, if there is ONLY change in pH and no change in CO2 or bicarb it is uncompensated

Hope that helps, it really helped me when looking at case studies :)

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