Iron toxicity

Background

• Each 325mg ferrous sulfate tablet contains 65mg of elemental iron
• Toxicity
  • Mild: 10-20mg elemental iron/kg
  • Moderate: 20-60mg/kg (approx 20-35 tablets)
  • Severe: >60mg/kg
• Absence of GI symptoms w/in 6hr of ingestion excludes significant iron ingestion

Pathophysiology

• GI tract irritant:
  • N/V, diarrhea, abdominal pain, bleeding
• Electron transport chain disruption:
  • Lactic acidosis
• Portal vein iron delivery to liver:
  • Hepatotoxicity
• Thrombin formation inhibition:
  • Coagulopathy

Clinical Features

1. Stage 1 (GI)
   1. Occurs within 6hr
   2. Abdominal pain, vomiting, diarrhea
2. Stage 2 (latent)
   1. May not always occur
   2. 6-24hr interval following ingestion during which GI symptoms resolve but damage continues
3. Stage 3 (systemic)
   1. Lactic acidosis
   2. Shock
   3. Coagulopathy
   4. Renal failure
   5. Cardiomyopathy
4. Stage 4 (Hepatic)
   1. 2-5 days after ingestion
   2. Elevated transaminases; may progress to hepatic failure
5. Stage 5 (Delayed sequelae)
   1. Gastric outlet obstruction (rare); occurs 4-6 weeks after ingestion

Work-Up

1. CBC
2. Chemistry
   1. Anion gap metabolic acidosis
3. Coags
4. LFTs
5. Iron levels
6. UA
   1. Used to follow efficacy of Fe chelation (urine changes from rusty color to clear)
7. T&S

Diagnosis

• Serum Iron Concentration
  • Interpret w/ caution: low serum iron levels do not necessarily mean absence of toxicity
  • Levels
    • <300: nontoxic or mild
    • 300-500: Significant GI symptoms and potential for systemic toxicity
    • >500: Moderate to severe systemic toxicity
    • >1000: severe systemic toxicity and increased morbidity

Treatment

1. Asymptomatic pt w/ ingestion of <20mg/kg only requires observation x6hr
2. Volume resuscitation
3. GI decontamination
   1. Consider only for large overdose w/ visible pills in the stomach on x-ray
      1. Whole-bowel irrigation (polyethylene glycol)
         1. Children: 250-500mL/hr
         2. Adults: 2L/hr
      2. Orogastric lavage
   2. Charcoal is not effective
4. Deferoxamine
   1. Indications:
      1. Systemic toxicity
      2. Metabolic acidosis
      3. Progressive symptoms
      4. Serum iron level >500
   2. Dosing:
      1. 1000mg IV; start at 5mg/kg/hr, increase up to 15mg/kg/hr as tolerated
      2. Subsequent doses are 500mg increments guided by clinical status of pt / urine color
      3. Recommended amount during first 24hr is 360mg/kg or 6gm
   3. Side effects:
      1. Hypotension (pre-existing hypotension is NOT a contraindication to therapy)
      2. Long-term use: mucor, renal failure, sepsis
5. Other therapies
   1. Dialysis (removes deferoxamine-iron complex in renal failure pts)
   2. Exchange transfusion

Disposition

• Discharge after 6hr obs for asymptomatic (or only vomited 1-2x) AND ingestion <20mg/kg
• Admit to ICU if deferoxamine required

See Also

Toxidromes

Source

• Tintinalli