Metabolic Acidosis

Normal Anion Gap Metabolic Acidosis

• U            Ureteric diversion
• S             Small bowel fistula
• E             Extra chloride (ED resuscitation) or HCl ingestion
• D            DKA (resolving)
• C             Carbonic anhydrase inhibitors
• A             Addisons (Type 4 RTA)
• R             Renal tubular acidosis types 1, 2, and 4
• P             Pancreatic fistula

Increased Anion Gap Metabolic Acidosis

• M            Methanol (formic acid), metformin
• U            Uraemia (including aminoglycosides)
• R            Renal failure (Uric acid)
• K            Ketoacidosis (alcohol, diabetes (acute), starvation)
• L            Lactic acidosis
• E            Ethanol
• S            Salicylates
• E            Ethylene glycol (glycolic acid)
• P            Paraldehyde, propylene glycol
• T            Toluene
• I             Iron, isoniazid
• C            Cyanide and carbon monoxide

Low Anion Gap

• Increase in unmeasured cations (Increased Li, K, Ca, Mg, and IgG)
  • Lithium toxicity
  • Hypercalcaemia
  • Hypermagnesaemia
  • Hyperkalaemia
  • IgG (Multiple Myeloma)
• Decreased unmeasured anions (Decreased PO4, albumin)
  • HYPOalbuminaemia, HYPOphosphatemia
• Chloride over-estimation (anion)
  • Bromide toxicity (Read as increased chloride)
  • Iodide toxicity
  • Hypercholesterolemia

Clinical

• Respiratory
  • Hyperventilation
  • Shift of Oxy-Hb curve to right
• Cardiovascular
  • Myocardial depression
  • Tissue catecholamine resistance
  • Pulmonary vasoconstriction
  • Hyperkalaemia

Correction

• Treat underlying cause
• Supportive therapy
• IV bicarbonate controversial – usually not helpful