Toxicology 14: Iron Ingestion Portal
Iron ingestions are notoriously difficult to assess. Shock and hepatic failure may appear after apparent recovery.
The estimation of elemental iron ingestion is dependent on the type of tablet ingested: ferrous sulfate contains 20% elemental iron; ferrous fumarate contains 32% elemental iron; ferrous gluconate contains 10% elemental iron.
The lethal dose of elemental iron is 200 to 250 mg/kg. GI symptoms may occur after 10 to 30 mg/kg.
The Pathophysiology of Iron Toxicity Follows Four Stages:
GI stage with vomiting, diarrhea, abdominal pain, and GI bleeding caused by a direct injury to the mucosa of the stomach and gut.
Relative stability stage that lasts only a few hours during which the patient may be acidotic and poorly perfused.
Shock stage with circulatory failure, profound hypotension, lactic acidosis, acidosis due to the circulating iron, and hypovolemia. This stage may result in death.
Hepatotoxicity stage appears within 48 hours and may also be lethal. Because of the difficulty estimating the amount of elemental iron ingested, serum iron levels to help predict the course. Iron levels < 300 µg/dL drawn 2 to 6 hours after the ingestion predicts a benign course. Levels > 500 µg/dL predict a severe course. An abdominal x-ray is useful because most iron preparations are visible on x-ray. If concretions of tablets are seen in the stomach, surgery may be indicated for removal.
Management
When the patient has severe symptoms, aggressive supportive management is needed for all of the manifestations of toxicity. Treat hypovolemia and shock aggressively, obtaining frequent blood gases to guide treatment for acidosis. (Large volumes of sodium bicarbonate may be needed to treat acidosis.)
Charcoal is not useful. Whole bowel irrigation may be indicated according to the estimated amount of iron present. Consult your toxicologist or poison center regarding this necessity.
After blood volume has been restored to normal, begin chelation therapy with deferoxamine. The standard dose is 15 mg/kg/h up to 6 grams per day, but it is important to start at 1 mg/kg/h and increase slowly over 20 minutes to avoid hypotension. Under some circumstances, higher infusion rates and daily dosages have been recommended. Maintain a good urine output to enable the excretion of the iron deferoxamine complex.
If renal failure ensues, charcoal hemoprofusion is indicated.
Consult freely about these complex patients.