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

• Irritant to GI tract: N/V, diarrhea, abdominal pain, bleeding
• Disrupts electron transport chain: lactic acidosis
• Portal vein delivers iron to liver: hepatotoxicity
• Inhibition of thrombin formation: 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
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

Source

• Tintinalli