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
- Stage 1 (GI)
- Occurs within 6hr
- Abdominal pain, vomiting, diarrhea
- Stage 2 (latent)
- May not always occur
- 6-24hr interval following ingestion during which GI symptoms resolve but damage continues
- Stage 3 (systemic)
- Lactic acidosis
- Shock
- Coagulopathy
- Renal failure
- Cardiomyopathy
- Stage 4 (Hepatic)
- 2-5 days after ingestion
- Elevated transaminases; may progress to hepatic failure
- Stage 5 (Delayed sequelae)
- Gastric outlet obstruction (rare); occurs 4-6 weeks after ingestion
Work-Up
- CBC
- Chemistry
- Coags
- LFTs
- Iron levels
- UA
- Used to follow efficacy of Fe chelation (urine changes from rusty color to clear)
- 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
- Asymptomatic pt w/ ingestion of <20mg/kg only requires observation x6hr
- Volume resuscitation
- GI decontamination
- Consider only for large overdose w/ visible pills in the stomach on x-ray
- Whole-bowel irrigation (polyethylene glycol)
- Children: 250-500mL/hr
- Adults: 2L/hr
- Orogastric lavage
- Whole-bowel irrigation (polyethylene glycol)
- Charcoal is not effective
- Consider only for large overdose w/ visible pills in the stomach on x-ray
- Deferoxamine
- Indications:
- Systemic toxicity
- Metabolic acidosis
- Progressive symptoms
- Serum iron level >500
- Dosing:
- 1000mg IV; start at 5mg/kg/hr, increase up to 15mg/kg/hr as tolerated
- Subsequent doses are 500mg increments guided by clinical status of pt / urine color
- Recommended amount during first 24hr is 360mg/kg or 6gm
- Side effects:
- Hypotension (pre-existing hypotension is NOT a contraindication to therapy)
- Long-term use: mucor, renal failure, sepsis
- Indications:
- Other therapies
- Dialysis (removes deferoxamine-iron complex in renal failure pts)
- Exchange transfusion
Source
- Tintinalli