Acid-Base disorders

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I'm hoping someone can help me understand some acid-base disorders. I can look at an ABG and determine whether it's acidosis, alkaloisis, compensated or uncompensated. But that's the easy stuff. I have problems determining whether it's renaL compensated or metabolic compensated. It's the HCO3_ that confuses me. Can someone explain to me when the bicarbonate level is below normal what that actually means, same with it being too high. I really appreciate it! Thank you all...

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Specializes in OB, ortho/neuro, home care, office.

Anything to do with the HCO3 is metabolic, CO2 is respiratory :)

Hope this helps

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Specializes in Trauma ICU, MICU/SICU.

First of all make sure you memorize your normals:

pH 7.35 - 7.45

CO2 35 - 45

HCO3 22 - 26

I've left out O2 since you are interested only in acidosis/alkalosis

Metabolic means it starts metabolically (HCO3). For example:

pH 7.25 (Acidosis)

CO2 40 (Normal - uncompensated)

HC03 20 (Acidic)

Uncompensated Metabolic Acidosis

Respiratory means it starts respiratorally:

pH 7.25 (Acidosis)

CO2 50 (Acidic)

HCO2 24 (Normal - uncompensated)

Uncompensated Respiratory acidosis

When it is partially compensated you look to see which value is closest to the pH and that will be your problem value - for example:

pH 7.25 (Acidosis)

CO2 50 (Acidic)

HCO3 27 (Alkaline - but going in opp direction of problem - partially compensating)

Partially compensated Respiratory acidosis

More examples:

pH 7.48 (Alkalosis)

CO2 46 (Acidic)

HCO3 30 (Alkaline)

Partially compensated Metabolic Alkalosis

pH 7.45 (normal - but leaning toward alkalosis)

CO2 46 (Acidic)

HCO3 32 (Alkaline)

Fully compensated (pH is normal) Metabolic (problem value) Alkalosis

pH 7.35 Normal (leaning toward acidosis)

CO2 50 (Acidic)

HCO3 27 Alkaline (compensating)

Fully compensated (pH is normal) respiratory (problem value) acidosis.

pH 7.26 (acidosis)

CO2 48 (acidic)

HCO3 21 (acidic)

Mixed acidosis

pH 7.48 (alkalosis)

CO2 32 (alkaline)

HCO3 28 (alkaline)

Mixed alkalosis

Hope this helps!

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Specializes in Cardiac/Telemetry.
First of all make sure you memorize your normals:

pH 7.35 - 7.45

CO2 35 - 45

HCO3 22 - 26

I've left out O2 since you are interested only in acidosis/alkalosis

Metabolic means it starts metabolically (HCO3). For example:

pH 7.25 (Acidosis)

CO2 40 (Normal - uncompensated)

HC03 20 (Acidic)

Uncompensated Metabolic Acidosis

Respiratory means it starts respiratorally:

pH 7.25 (Acidosis)

CO2 50 (Acidic)

HCO2 24 (Normal - uncompensated)

Uncompensated Respiratory acidosis

When it is partially compensated you look to see which value is closest to the pH and that will be your problem value - for example:

pH 7.25 (Acidosis)

CO2 50 (Acidic)

HCO3 27 (Alkaline - but going in opp direction of problem - partially compensating)

Partially compensated Respiratory acidosis

More examples:

pH 7.48 (Alkalosis)

CO2 46 (Acidic)

HCO3 30 (Alkaline)

Partially compensated Metabolic Alkalosis

pH 7.45 (normal - but leaning toward alkalosis)

CO2 46 (Acidic)

HCO3 32 (Alkaline)

Fully compensated (pH is normal) Metabolic (problem value) Alkalosis

pH 7.35 Normal (leaning toward acidosis)

CO2 50 (Acidic)

HCO3 27 Alkaline (compensating)

Fully compensated (pH is normal) respiratory (problem value) acidosis.

pH 7.26 (acidosis)

CO2 48 (acidic)

HCO3 21 (acidic)

Mixed acidosis

pH 7.48 (alkalosis)

CO2 32 (alkaline)

HCO3 28 (alkaline)

Mixed alkalosis

Hope this helps!

Thank you for that. It sure helps ME understand. Acidosis and alkalosis has always been a bit "cloudy" for me. Thanks again.

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Specializes in Trauma ICU, MICU/SICU.
Thank you for that. It sure helps ME understand. Acidosis and alkalosis has always been a bit "cloudy" for me. Thanks again.

Your welcome!!! I had a great teacher for ABG's.

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This is an area which is somewhat difficult for me to understand. Anyways, what does compensated and uncompensated mean and how would you know if its metabolic or respiratory?

:eek:

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Specializes in Trauma ICU, MICU/SICU.

I'll try to do this quick and dirty:

First the normal ranges...

7.35 - 7.45 is normal with 7.40 being ideal. The lower the pH the more acidic it is, the higher the pH, the more alkaline it is.

CO2 normal is 35 - 45; the higher the CO2, the more acidic (CO2 makes the blood acidic).

HCO3 normal is 22 - 26; The higher the HCO3 the more alkaline, the lower the more acidic (HCO3 makes it alkaline).

Respiratory acidosis, means your lungs are causing the problem (high CO2, Low pH is resp acidosis; low CO2, high pH is respiratory alkalosis).

Compensating is when the oppposite system of the problem, is compensating. For instance if someone has respiratory acidosis, the kidneys will call for an increase in HCO3 to compensate (this takes several days however).

So let's look at an abnormal ABG:

pH 7.33 (acidic)

CO2 48 (too much CO2, acidic)

HCO3 24 (dead normal HCO3 - uncompensated):

Uncompensated Respiratory Acidosis

pH 7.33 (acidic)

CO2 48 (too much CO2, acidic)

HCO3 28 (increased HCO3 trying to compensate):

Partially Compensated Respiratory Acidosis.

So if you look at this post and my previous post, it should be clear as mud. :uhoh3:

Hope this helps!

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Thank you, I will go over it and over it, untill I get it.

Appreciate your help :)

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pH 7.25 (Acidosis)

CO2 50 (Acidic)

HCO3 27 (Alkaline - but going in opp direction of problem - partially compensating)

Partially compensated Respiratory acidosis

How do you know this is respiratory or metabolic? I thought the 'off' item would be in the same direction as the pH. Thanks all

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