Metabolic Acidosis

Double-Helix, BSN, RN · Mar 2, 2017

Part of the function of the kidneys are to promote excretion of acid anions and produce bicarbonate in order to achieve acid/base balance. When the kidney is damaged and not fully functioning, acid builds up and bicarb levels decrease. When bicarb levels decrease, the body tries to compensate for this by reducing CO2 levels. I'm sure you know that when you exhale, you are exhaling CO2. The more you exhale, the more CO2 you blow off. So the tachypnea is the body's way of trying to lower CO2 levels in response to the lower bicarb.

Editorial Team / Admin · Mar 2, 2017

We at AN are happy to help with homework, but we ask that you show what you've found first and where you are stuck.

Do you know what role the kidneys play in acid-base balance? Then think about how CKD changes that.

IvyRN2017, ASN, CNA, RN · Mar 2, 2017

Actually this isn't homework but thanks so much for making me feel silly for even asking.

AceOfHearts<3 · Mar 2, 2017

I found the free Simple Nursing videos on YouTube about acid-base imbalance very helpful when in school. Simple Nursing requires a subscription fee to access most of their content, but some is posted for free on YouTube. Take a look- that might help you out some. I think Double-Helix did a great job too.

Esme12, ASN, BSN, RN · Mar 2, 2017

Actually this isn't homework but thanks so much for making me feel silly for even asking.

No one is trying to make anyone feel silly.

Here at AN we want to help students become the best nurses that they can become.

What semester are you?

Think back to acid base balance and ABG's. What does the body need to do to correct METABOLIC ACIDOSIS?

respiratory opposite

ph elevated pco2 diminished = respiratory alkalosis
ph diminished pco2 elevated = respiratory acidosis

metabolic equal

ph elevated hco3 elevated = metabolic alkalosis
ph diminished hco3 diminished = metabolic acidosis

Esme12, ASN, BSN, RN · Mar 2, 2017

Normal values:

PH = 7.35 - 7.45

C02 = 35 - 45

HC03 = 21-26

Respiratory acidosis = low ph and high C02

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

*Compensated by metabolic alkalosis (increased HC03)

For example:

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, diuretics

*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.

Now a simple way to remember this......

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).

Here is 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.

KelRN215, BSN, RN · Mar 6, 2017

If you have a metabolic acidosis, the body is going to use the respiratory system to compensate. CO2 is an acid. Hyperventilation = blowing off CO2 = using the lungs to decrease the excess of acid in the body.