? about acidosis/alkalosis ctxt

NurseFirst · Feb 1, 2005

In simple and easy terms explain
metabolic acidosis/alkalosis
and
Respirtory acidosis/alkalosis
I tried really hard to understand the teacher and It DIDNt sink in.
So In simple terms could someone explain these terms.
Thanks!!!!!!!!!!!!!!

Okay: first thing, find out what the pH is.

7.35-7.45 is normal

>7.45 is alkalosis

To find out whether it is respiratory or metabolic you need to know the HCO-3 and the paCO-2 values--and the normal values.

If the HCO-3 is out-of-whack and not the paCO-2, what ever is happening is metabolic, and the body uses the respiratory system to compensate. For example, in DKA, pts breath deeply (Kussmaul) in order to blow off CO-2. This helps the body to become more alkalotic.

If the paCO-2 is out-of-whack and not the HCO-3, what ever is happening is respiratory. The body uses the kidneys to adjust the pH.

One method is to draw a diagram, showing acidotic normal alkalotic on top and the pH, HCO-3 and paCO-2 values along the side. Then you determine which values represent what. I've forgotten the exact values at the moment, but I can tell you that in respiratory conditions, the paCO-2 values move opposite to the pH values. In metabolic conditions, the HCO-3 values move in the same direction as the pH.

If the pH is within the normal range, but the HCO-3 and paCO-2 values are out-of-whack, it means that the body has compensated for the disturbance in the primary system (resp or metabolic). If the pH is less than 7.4, then the body is compensating an acidosis; if the pH is > 7.4, the body is compensating an alkalosis. You then find out which, the HCO-3 or the paCO-2 value falls on the same side as the pH. If it's the HCO-3, it is metabolic; if it is the paCO-2, it is respiratory.

Hope that helps.

NurseFirst

begalli · Feb 2, 2005

Normal values:

PH = 7.35 - 7.45

C02 = 35 - 45

HC03 = 21-26 (can vary by facility)

Respiratory acidosis = low ph and high C02

hypoventilation (eg: COPD, narcs or sedatives, atelectasis)

*Compensated by metabolic alkalosis (increased HC03)

examples:

ph 7.20 C02 60 HC03 24 (uncompensated respiratory acidosis)

ph 7.33 C02 55 HC03 29 (partially compensated respiratory acidosis)

ph 7.37 C02 60 HC03 37 (compensated respiratory acidosis)

Respiratory alkalosis = high ph and low C02

hyperventilation (eg: anxiety, PE, pain, sepsis, brain injury)

*Compensated by metabolic acidosis (decreased HC03)

examples:

ph 7.51 C02 26 HC03 25 (uncompensated respiratory alkalosis)

ph 7.47 C02 32 HC03 20 (partially compensated respiratory alkalosis)

ph 7.43 C02 30 HC03 19 (compensated respiratory alkalosis)

Metabolic acidosis = low ph and low HC03

diabetic ketoacidosis, starvation, severe diarrhea

*Compensated by respiratory alkalosis (decreased C02)

examples:

ph 7.23 C02 36 HC03 14 (uncompensated metabolic acidosis)

ph 7.31 C02 30 HC03 17 (partially compensated metabolic acidosis)

ph 7.38 C02 26 HC03 20 (compensated metabolic acidosis)

Metabloic alkalosis = high ph and high HC03

severe vomiting, potassium deficit, dieuretics

*Compensated by respiratory acidosis (increased C02)

example:

ph 7.54 C02 44 HC03 29 (uncompensated metabolic alkalosis)

ph 7.50 C02 49 HC03 32 (partially compensated metabolic alkalosis)

ph 7.44 C02 52 HC02 35 (compensated metabolic alkalosis)

*Remember that compensation corrects the ph.

I work with blood gases every single day, many times a day for years and still I got confused typing this info! :imbar

A good way to study this is to make flashcards.

Good luck with your studies!

begalli · Feb 2, 2005

Here are some places you can practice:

http://realnurseed.com/abgm1.htm

http://classes.kumc.edu/son/nurs420/unit2/example1.html

http://classes.kumc.edu/son/nurs420/unit2/practiceabg.html

http://www.manuelsweb.com/abg.htm

http://www.nepeanicu.org/abgs.htm

This one has some nice basic case studies and walks you through the interpretation (see pages 9-17):

http://www.orhs.org/classes/nursing/ABG_2004.pdf

(acrobat reader needed)

ILuvBabies2005 · Feb 8, 2005

Hi! This helped me understand it a little better...

CO2 = acid, makes things acidic

HCO3 = base, makes things alkalotic

Remember ROME

R-Respiratory

O-Opposite

M-Metabolic

E-Equal

Ok always look at the pH first...

pH

pH>7.45 = alkalosis

Then, if the CO2 is high or low, then it is respiratory...If the HCO3 is high or low then it is metabolic. How you remember that is that the respiratory system is involved with CO2 (blowing air off or slowing RR), and the kidneys (metabolic) are involved with HCO3 (excreting or not excreting).

Example (Here's how you think thru it):

pH = 7.25 CO2 = 40 HCO3 = 17

Ok, first, the pH is low so think acidosis. CO2 is WNL. HCO3 is low. Draw arrows if it helps. The abnormal values are both low (think Equal). Metabolic imbalances are equal. So, this must be metabolic acidosis!

Now, for compensation...

If you have a metabolic imbalance, the respiratory system is going to try to compensate. Respiratory = CO2. If the CO2 is normal in the ABG, then there is no compensation going on. Compensation in acidosis will decrease the CO2 because you want to get rid of the acid (CO2). In alkalosis, it will increase because you want to add more acid (CO2)

If you have a respiratory imbalance, the kidneys will try to compensate. Kidneys = HCO3. If the HCO3 is normal in the ABG, then there is no compensation going on. Compensation in acidosis will increase HCO3 because you want to hold on to the base to make it more alkalotic. In alkalosis, it will decrease because you want to excrete the base to make it more acidic.

I know this can be confusing just reading it but it has always helped me to look at it on paper and draw little up/down arrows and rationalize the changes. Work several ABGs for practice. Hope this helps and good luck! :)

sj73201, BSN, RN · Apr 29, 2010

Hi! This helped me understand it a little better...
CO2 = acid, makes things acidic
HCO3 = base, makes things alkalotic
Remember ROME
R-Respiratory
O-Opposite
M-Metabolic
E-Equal
Ok always look at the pH first...
pH
pH>7.45 = alkalosis
Then, if the CO2 is high or low, then it is respiratory...If the HCO3 is high or low then it is metabolic. How you remember that is that the respiratory system is involved with CO2 (blowing air off or slowing RR), and the kidneys (metabolic) are involved with HCO3 (excreting or not excreting).
Example (Here's how you think thru it):
pH = 7.25 CO2 = 40 HCO3 = 17
Ok, first, the pH is low so think acidosis. CO2 is WNL. HCO3 is low. Draw arrows if it helps. The abnormal values are both low (think Equal). Metabolic imbalances are equal. So, this must be metabolic acidosis!
Now, for compensation...
If you have a metabolic imbalance, the respiratory system is going to try to compensate. Respiratory = CO2. If the CO2 is normal in the ABG, then there is no compensation going on. Compensation in acidosis will decrease the CO2 because you want to get rid of the acid (CO2). In alkalosis, it will increase because you want to add more acid (CO2)
If you have a respiratory imbalance, the kidneys will try to compensate. Kidneys = HCO3. If the HCO3 is normal in the ABG, then there is no compensation going on. Compensation in acidosis will increase HCO3 because you want to hold on to the base to make it more alkalotic. In alkalosis, it will decrease because you want to excrete the base to make it more acidic.
I know this can be confusing just reading it but it has always helped me to look at it on paper and draw little up/down arrows and rationalize the changes. Work several ABGs for practice. Hope this helps and good luck! :)

OMG! I can't explain in enough words how much this helped AND saved me! I have a patho test tomorrow & i was clueless about acid-base and almost to tears! Again, thank you soooo very much. It really helped me, tremendously!! God bless