Rule of 80's
Rule of 80's is a method of interpreting a person's acid-base status using an arterial blood gas. It is a quick way to determine if a patient has metabolic acidosis, metabolic alkalosis, respiratory acidosis, or respiratory alkalosis. It does not say anything AbOUT the cause of the acid-base disturbance.
Method
Step |
Procedure |
Example |
|---|---|---|
1 |
Look at pH and pCO2 |
pH = 7.30 |
2 |
Take decimal from pH and add it pCO2 |
30 + 35 = 65 |
This number is used to determine if the patient has a pure respiratory issue (number of 77-83), a metabolic acidemia component (number less than 77), or a metabolic alkalemia component (number greater than 83).
Step |
Procedure |
Example |
|---|---|---|
3 |
Look at pCO2 |
pCO2 = 35 |
If this number is less than 40 there is a respiratory alkalemia component, and if this number is greater than 40 there is a respiratory acidemia component.
Step |
Procedure |
Example |
|---|---|---|
4 |
Look at pH |
pH = 7.30 |
If the patient has a pH less than 7.40, it is an acidosis. If the pH is greater than 7.40, it is an alkalosis. This is The Primary process.
If the pH = 7.40, nothing is termed "-osis". The acidemia and alkalemia remain named as is.
Step |
Procedure |
Example |
|---|---|---|
5 |
Rename the primary process |
Metabolic acidemia becomes |
If the patient has an acidosis, the metabolic or respiratory acidemia is termed a metabolic or respiratory acidosis. If the patient has an alkalosis, the metabolic or respiratory alkalemia is termed a metabolic or respiratory alkalosis.
Step |
Procedure |
Example |
|---|---|---|
6 |
Final interpretation |
Metabolic acidosis with respiratory alkalemia |
Examples
pH |
pCO2 |
Interpretation |
|---|---|---|
7.20 |
60 |
Pure respiratory acidosis |
7.60 |
20 |
Pure respiratory alkalosis |
7.20 |
20 |
Metabolic acidosis with respiratory alkalemia |
7.50 |
50 |
Metabolic alkalosis with respiratory acidemia |
References
Schrier's Diseases of the Kidney