When thinking about iron, the first thing that must be done is to convert the amount of iron taken, to the amount of elemental iron ingested. This varies considerably between different types of iron tablets, depending on the type of ferrous or ferric salt:
ferrous sulfate (dried) — divide dose by 3.3
ferrous sulfate (heptahydrate) — divide dose by 5
ferrous gluconate — divide dose by 9
ferrous fumarate — divide dose by 3
ferric chloride — divide dose by 3.5
ferrous chloride — divide dose by 4
You can then risk stratify, by the amount of elemental iron they have ingested:
<20mg/kg –– asymptomatic
20-60mg/kg –– GI symptoms only
60-120mg/kg –– potential for systemic toxicity
>120mg/kg –– potentially lethal
Peak serum iron levels occur 4-6 hours following iron ingestion, then levels fall due to intracellular shift. Levels do not clearly correlate with clinical toxicity, but > 90 micromol/L (500 mcg/dL) is generally considered predictive of systemic toxicity (equivalent to >60mg/kg)
Local Effects - corrosive injury to the GI mucosa (vomiting, diarrhoea, haematemeis, melaena) . Can lead to gastric strictures.
Systemic Effects - cellular toxin, targeting the cardiovascular syndrome. Severe lactic acidosis from hypoperfusion due to volume loss, vasodilation and negative inotropic effects.
Blood gas - can look like DKA. Anion gap metabolic acidosis.
BMs - can be hyperglycaemic
LFTs, Coags — hepatic failure
U&E — renal failure
**Not adsorbed by activated charcoal**
Whole bowel irrigation for ingestion >60mg/kg
Surgical or endoscopy removal if >120mg/kg or WBI not feasible
level >90 micromol/L at 4-6 hours post-ingestion
evidence of systemic toxicity
altered mental status
Chelates free irons that can be renally excreted. Ferrioxamine is then excreted unchanged in the urine which classically, not reliably, turns a vin rose colour.
15 mg/kg/h, reduced if hypotension occurs, may be titrated up to 40mg/kg/h in severe toxicity
cardiac monitoring is mandatory. Can cause hypersensitivity, ARDS, toxic retinopathy or yersinia sepsis. Can be stopped when the patient is stable and serum iron is <60micromol/L - usually 56 hours.