Metabolic acidosis DDx

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

References and Links


CCC 700 6

Critical Care

Compendium

Emergency physician MA (Oxon) MBChB (Edin) FACEM FFSEM with a passion for rugby; medical history; medical education; and informatics. Asynchronous learning #FOAMed evangelist. Co-founder and CTO of Life in the Fast lane | Eponyms | Books | vocortex |

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