Makindo Medical Notes

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Iron toxicity is potentially lethal - check local/national poisons advice. Rapid assessment and treatment are critical, especially in children, as toxicity can progress swiftly.

About

• Iron is commonly used in supplements and for treating iron deficiency anaemia, making it readily available in households.
• Toxicity risks are high with iron supplements and are especially dangerous in children due to smaller body mass and higher absorption rates.
• Iron overdose can lead to multisystem complications, including severe metabolic, cardiovascular, and hepatic disturbances.

Dose and Toxicity Thresholds

• Mild GI Symptoms: 20-60 mg/kg of elemental iron typically causes nausea, vomiting, and abdominal pain.
• Systemic Toxicity: 60-120 mg/kg results in potential organ toxicity, metabolic acidosis, and can lead to multisystem involvement.
• Lethal Dose: >120 mg/kg is associated with severe toxicity, coma, cardiovascular collapse, and can be fatal without intervention.

Clinical Features

• Minor overdoses often present as gastrointestinal symptoms (nausea, vomiting, abdominal pain, diarrhoea).
• More severe cases can lead to systemic effects:
  • Early (0-6 hours): GI bleeding, haematemesis, melena, diarrhoea, metabolic acidosis, shock.
  • Latent Phase (6-24 hours): Temporary improvement, which can be misleading and may delay treatment.
  • Systemic Toxicity (24-48 hours): Cardiovascular shock, hepatotoxicity, renal failure, metabolic acidosis, coagulopathy.
  • Late Effects (2-6 weeks): Risk of liver fibrosis, gastrointestinal strictures, and scarring.

Investigations

• Iron Levels: Measure serum iron levels 4-6 hours post-ingestion to assess toxicity level; levels >90 micromoles/L indicate severe toxicity.
• Blood Tests: U&E, LFTs, glucose, lactate, bicarbonate, and arterial blood gas (ABG) to assess acidosis.
• Imaging: Abdominal X-ray (AXR) to detect radiopaque iron tablets, helping to estimate ingestion amount.
• Metabolic Acidosis: Anion gap acidosis is common in severe toxicity; a fall in bicarbonate is a marker of toxicity.

Management

• Initial Stabilisation: ABCs (airway, breathing, circulation), IV fluid resuscitation, and oxygen as needed.
• Whole Bowel Irrigation: For large ingestions (>60 mg/kg), especially if tablets are visible on AXR, to remove unabsorbed iron.
• Decontamination: Activated charcoal is generally ineffective for iron overdose but may be given within 1 hour if combined overdose with other drugs.

Desferrioxamine Therapy

• Indicated for patients with severe toxicity or serum iron levels >90 micromoles/L at 4-6 hours post-ingestion.
• Administration:
  • Intramuscular (IM): Preferred in non-shocked patients. Initial dose of 1000 mg IM, followed by 500 mg every 4 hours for two doses; further doses at 500 mg every 4-12 hours if needed (do not exceed 6000 mg in 24 hours).
  • Intravenous (IV): For severe toxicity or shock; administer 15 mg/kg/hr up to a maximum of 80 mg/kg in 24 hours.
  • Chelated iron appears as a distinct orange-red urine, indicating effective chelation.
• Additional Monitoring: Monitor urine output, as oliguria may indicate renal involvement and warrant adjustment in therapy.

Complications

• Gastrointestinal: Risk of GI bleeding and perforation.
• Hepatic Injury: Progressive liver dysfunction, coagulopathy, and potential failure within 48 hours.
• Metabolic Complications: Severe acidosis and electrolyte imbalance may complicate management.
• Delayed Effects: Weeks post-ingestion, patients may develop strictures or obstructions in the GI tract due to scarring.

References

• Iron Toxicity Management (Toxbase)