Metabolic Acidosis

Anion gap = ( [Na+] + [K+] ) − ( [Cl] + [HCO3] )

Increased anion gap:

     MUDPILES pneumonic

  • M-Methanol
  • U-Uremia (chronic kidney failure) – accumulation of sulfates, phosphates, urea; massive rhabdomyolysis
  • D-Diabetic ketoacidosis
  • P-Propylene glycol (“P” used to stand for Paraldehyde but this substance is not commonly used today)
  • I-Infection, Iron, Isoniazid, Inborn errors of metabolism
    • Intoxication: organic acids (salicylates, ethanol, methanol, formaldehyde, ethylene glycol, paraldehyde, isoniazid)
  • L-Lactic acidosis
  • E-Ethylene glycol (Note: Ethanol is sometimes included in this mnemonic as well, although the acidosis caused by ethanol is actually primarily due to the increased production of lactic acid found in such intoxication.)
  • S-Salicylates

Normal anion gap

Causes include:

  • Longstanding diarrhea (bicarbonate loss)
  • Bicarbonate loss due to taking topiramate
  • Pancreatic fistula
  • Uretero-sigmoidostomy
  • Renal tubular acidosis (RTA)
  • Intoxication:
    • Ammonium chloride
    • Acetazolamide (Diamox)
    • Bile acid sequestrants
    • Isopropyl alcohol
  • Renal failure (occasionally)
  • Inhalant abuse
  • Toluene

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