38-37: Iron Overdose

Iron is widely used therapeutically for the treatment of anemia and as a daily supplement in multiple vitamin preparations. Most children's preparations contain about 12–15 mg of iron (as sulfate, gluconate, or fumarate salt) per dose, compared with 60–90 mg in most adult-strength preparations. Iron is corrosive to the gastrointestinal tract and, once absorbed, has depressant effects on the myocardium and on peripheral vascular resistance. Intracellular toxic effects of iron include disruption of Krebs cycle enzymes. Carbonyl iron is a powdered form of elemental iron. It is not as irritating to the gastrointestinal tract as the iron salts and appears to be safer.

CLINICAL FINDINGS

Ingestion of less than 30 mg/kg of iron usually produces only mild gastrointestinal upset. Ingestion of more than 40–60 mg/kg may cause vomiting (sometimes with hematemesis), diarrhea, hypotension, and acidosis. Death may occur as a result of profound hypotension due to massive fluid losses and bleeding, metabolic acidosis, peritonitis from intestinal perforation, or sepsis. Fulminant hepatic failure may occur. Survivors of the acute ingestion may suffer permanent gastrointestinal scarring.

Serum iron levels greater than 350–500 mcg/dL are considered potentially toxic, and levels greater than 1000 mcg/dL are usually associated with severe poisoning. A plain abdominal radiograph may reveal radiopaque tablets.

TREATMENT

A. Emergency and Supportive Measures

Treat hypotension aggressively with intravenous crystalloid solutions (0.9% saline or lactated Ringer solution). Fluid losses may be massive owing to vomiting and diarrhea as well as third-spacing into injured intestine.

Perform whole bowel irrigation to remove unabsorbed pills from the intestinal tract (see above). Activated charcoal is not effective but may be appropriate if other ingestants are suspected.

B. Specific Treatment

Deferoxamine is a selective iron chelator. It is not useful as an oral binding agent. For patients with established manifestations of toxicity—and particularly those with markedly elevated serum iron levels (eg, greater than 800–1000 mcg/dL)—administer 10–15 mg/kg/h by constant intravenous infusion; higher doses (up to 40–50 mg/kg/h) have been used in massive poisonings. Hypotension may occur. The presence of an iron-deferoxamine complex in the urine may give it a "vin rosé" appearance. Deferoxamine is safe for use in pregnant women with acute iron overdose. Caution: Prolonged infusion of deferoxamine (more than 36–48 hours) has been associated with development of acute respiratory distress syndrome (ARDS)—the mechanism is not known.