Metabolic Acidosis due to Iron Overdose

Iron - the "I" in Mudpiles

Iron overdose as a cause of a high anion gap metabolic acidosis

Now, iron is usually mentioned as an important cause of metabolic acidosis, and there is a warm spot reserved for it in the “MUDPILES” mnemonic. An impressionable person might be inclined to believe that iron contributes to the high anion gap metabolic acidosis by dissociating into unmeasured anions, much like the toxic alcohols. However, that would be wildly inaccurate, because iron is a cation.

The acidosis here is multifactorial. Some textbooks (Fowler’s Handbook on the Toxicology of Metals) suggest that the acidosis is mainly due to the physicochemical effects of the iron ion itself. Other sources (Goldfranks Manual of Toxicologic Emergencies) attribute the acidosis to a raised lactate, of which not all is generated by direct effects of the iron, but rather due to the fluid loss (from an ulcerated gut), cardiogenic shock (due to the myocardial mitochondrial toxicity) and fulminant hepatic failure. On top of that, a fair portion of the lactic acidosis is due to the direct mitochondrial toxicity of iron in all tissues.