Acid/Base (alkalosis vs acidosis, metabolic vs respiratory)

This is the general way to approach an acid-base disturbance. They’re not really as bad as they seem at first. You just need to remember that CO2 is acidic and HCO3- is basic. So an increase in CO2 makes the body acidotic and an increase in HCO3- makes the body alkalotic.

It’s also good to remember to calculate the anion gap when doing these calculations.

AG = Na – (Cl- + HCO3-) it’s just the cations minus the anions. If this gap between the cations and anions is large, it means that the anions are stacking their team and have an extra anion helping out.

The classic mnemonic is MUDPILES

  • Methanol
  • Uremia
  • Diabetic ketoacidosis
  • Paraldehyde
  • Isopropyl alcohol
  • Lactic acidosis
  • Ethylene glycol
  • Salicylates

If the anion gap is big, it’s good to look at the ratio between the change in the gap and the change in the HCO3-.

  • Increase in AG < decrease in HCO3- = coexisting non-anion gap metabolic acidosis
  • Increase in AG > decrease in HCO3- = coexisting metabolic alkalosis

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