118 - anion gap basis - metabolic acidosis causes

The causes of a metabolic acidosis can be classified on the basis of a normal or elevated anion gap.

An elevated anion gap is created by inorganic (eg, phosphate or sulfate), organic (eg, ketoacids or lactate), or exogenous (eg, salicylate) acids incompletely neutralized by bicarbonate. Frequent causes of an elevated anion gap metabolic acidosis is represented by the mnemonic MUDPILES:

· Methanol

· Uremia

· Diabetic ketoacidosis

· Paraldehyde

· Iron, isoniazid (INH)

· Lactic acid

· Ethanol, ethylene glycol

· Salicylates

A normal anion gap metabolic acidosis occurs when loss of bicarbonate from the GI tract or kidneys is excessive or when hydrogen ions cannot be secreted because of renal failure. The causes can be represented by the mnemonic USEDCRAP:

· Ureterostomy

· Small bowel fistula

· Extra chloride

· Diarrhea

· Carbonic anhydrase inhibitors (eg, acetazolamide)

· Renal tubular acidosis

· Adrenal insufficiency

· Pancreatic fistula