Acidosis resident survival guide
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor-In-Chief: Rim Halaby
Overview
Acidosis occurs when the pH is less or equal to 7.35 due to excess of hydrogen ions.
Causes
2 main causes of primary acidosis in the body can be differentiated from each other based on ABG. Metabolic acidosis is caused by decreased amount of serum bicarbonate while respiratory acidosis is caused by increased CO2 retention in the body.
Metabolic acidosis itself is divided into 2 subcategories based on the calculated amount of anion gap.
High Anion Gap Metabolic Acidosis
Mnemonics are helpful to summarize them, last recent mnemonic involving almost all causes go elevated anion gap metabolic acidosis is"
CAT MUDPILES
- DKA (and other causes of Ketoacidosis)
- Isoniazide - Iron - Ibuprofen
Normal Anion Gap Metabolic Acidosis
- Diabetic ketoacidosis
- Diarrhea
- Ethylene glycol
- Lactic acidosis
- Methanol
- Renal tubular acidosis
- Salicylates
- Uremia
Management
| pH < 7.35 | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Acidosis (High [H+]) | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Determine the primary disorder Metabolic or respiratory? | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Check [HCO3-] and PaCO2 | |||||||||||||||||||||||||||||||||||||||||||||||||||
| Low [HCO3-] and Low to normal PaCO2 | High PaCO2 and High to normal [HCO3-] | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Metabolic acidosis | Respiratory acidosis | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Check for respiratory compensation Calculate expected PCO2 | Check for renal compensation Calculate expected [HCO3-] | ||||||||||||||||||||||||||||||||||||||||||||||||||
| Decrease in PaCO2=1.25 x (24- measured HCO3-)? | Acute acidosis? Increase [HCO3-]=0.1 x (measure PaCO2-40)? | Chronic acidosis? Increase [HCO3-]=0.1 x (measure PaCO2-40)? | |||||||||||||||||||||||||||||||||||||||||||||||||
| PaCO2 too low? Mixed metabolic acidosis with respiratory alkalosis | PaCO2 too high? Mixed metabolic acidosis with respiratory acidosis | [HCO3-] too low? Mixed respiratory acidosis with metabolic acidosis | [HCO3-] too high? Mixed respiratory acidosis with metabolic alkalosis | [HCO3-] too low? Mixed respiratory acidosis with metabolic acidosis | E04=[HCO3-] too high? Mixed respiratory acidosis with metabolic alkalosis | ||||||||||||||||||||||||||||||||||||||||||||||
| Measured PaCO2 is equal to expected value? Compensated metabolic acidosis | Measured [HCO3-] is equal to expected value? Compensated respiratory acidosis | Measured [HCO3-] is equal to expected value? Compensated respiratory acidosis | |||||||||||||||||||||||||||||||||||||||||||||||||
| Click here for the management of metabolic acidosis | Click here for the management of respiratory acidosis | ||||||||||||||||||||||||||||||||||||||||||||||||||