So I got pimped mercilously by my attending two days ago, while I was sick, feeling like crap, and had only seen my patient for like 20 minutes. So it never happens to you, I present the quick’n'dirty acid-base disorder step-by-step guide:
- Get a blood gas. Put it in ice, send it to the lab.
- Look at pH: Less than 7.4? Acidosis. Greater than 7.4? Alkalosis.
- Look at pCO2 and bicarb. Do they move in the same direction as the pH, or the opposite direction? (Nl pCO2 = 40, nl bicarb = 24.) If they move in the saME direction, it’s primary MEtabolic. If they move in a diffeREnt direction, it’s primary REspiratory.
- Is the non-primary system compenstating appropriately? (Calculate that with those annoying equations I can never remember.)
- Is there an anion gap? (Na – Cl – bicarb > 12) If no, you’re done.
- If yes, take the anion gap – 12. Add that to the bicarb level. If it’s greater than 26, you’ve got a metabolic alkalosis as well. If it’s less than 22, you’ve got a non-anion gap metabolic acidosis, too. Classic pimping: You can have 3 disorders co-existing, but not 4. (Your lungs can either be making respiratory acidosis or alkalosis, not both.)
And on to the mnemonics for the causes:
Anion Gap Metabolic Acidosis: MUDPILERS
- DKA/Alcoholic KA
- Lactic Acidosis
- Etoh/Ethylene Glycol
- Rhabdo/Renal Failure
Non-Anion Gap Acidosis: HARDUPS
- Renal Tubular Acidosis
- Uretero-Pelvic Shunt
Acute Respiratory Acidosis (Chronic Respiratory Acidosis = COPD/restrictive lung dz): any hypoventilation state
- CNS Depression (drugs/CVA)
- Airway Obstruction
- Pulmonary Edema
Metabolic Alkalosis: CLEVER PD
- Endo: Conn’s/Cushing’s/Bartter’s)*
- Excess Alkali*
- Refeeding Alkalosis*
* = Associated with High Urine Cl levels
Respiratory Alkalosis: CHAMPS (think speed up breathing)
- CNS disease
- Mech Ventilators