Iron Poisoning

Key Features

• Three common formulations with varying amounts of elemental iron

  • Ferrous fumarate (33%)

  • Ferrous sulfate (20%)

  • Ferrous gluconate (12%)

• Typically, doses of more than 20 mg/kg of elemental iron cause symptoms

Clinical Findings

• Five stages of intoxication may occur in iron poisoning

  • Hemorrhagic gastroenteritis, which occurs 30–60 minutes after ingestion and may be associated with shock, acidosis, coagulation defects, and coma; this phase usually lasts 4–6 hours

  • Phase of improvement, lasting 2–12 hours, during which patient looks better

  • Delayed shock, which may occur 12–48 hours after ingestion; metabolic acidosis, fever, leukocytosis, and coma may also be present

  • Liver damage with hepatic failure

  • Residual pyloric stenosis, which may develop about 4 weeks after the ingestion

Diagnosis

• Once iron is absorbed from the GI tract, it is not normally eliminated in feces but may be partially excreted in the urine, giving it a red color prior to chelation

• A reddish discoloration of the urine suggests a serum iron level > 350 mg/dL but is neither sensitive nor specific

• Urinary output should be monitored and urine sediment examined for evidence of renal tubular damage

• Initial laboratory studies should include

  • Blood typing and cross-matching

  • Total protein

  • Serum iron, sodium, potassium, and chloride

  • PCO₂

  • pH

  • Liver function tests

• Serum iron levels fall rapidly even if deferoxamine is not given

• After the acute episode, liver function studies and an upper GI series are indicated to rule out residual damage

Treatment

• GI decontamination is based on clinical assessment

• Gastric lavage and whole bowel irrigation should be considered in potentially life-threatening overdoses

• Shock is treated in the usual manner

• Deferoxamine

  • Specific chelating agent for iron, is a useful adjunct in the treatment of severe iron poisoning

  • Indications

    • Metabolic acidosis

    • Persistent symptoms

    • Shock

    • Serum iron determination cannot be obtained readily, or if the peak serum iron exceeds 400 mcg/dL (62.6 μmol/L) at 4–5 hours after ingestion

  • Dosages

    • For shock: 15 mg/kg/h intravenously; infusion rates up to 35 mg/kg/h have been used in life-threatening poisonings

    • If intravenous access unavailable, give 90 mg/kg intramuscularly every 8 hours (maximum, 1 g); procedure is painful

  • May be discontinued after 12–24 hours if the acidosis has resolved and the patient is improving

  • Side effects

    • Acute respiratory distress syndrome (ARDS) if given for more than 24 hours

    • Rapid intravenous administration can cause hypotension, facial flushing, urticaria, tachycardia, and shock

    • Contraindicated in patients with renal failure unless dialysis can be used

• Hemodialysis, peritoneal dialysis, or exchange transfusion can be used to increase the excretion of the dialyzable complex