What are the treatment options for urea fertilizer (urea) ingestion?

Treatment Options for Urea Fertilizer Ingestion

Immediate hemodialysis is the primary treatment for urea fertilizer ingestion to prevent methaemoglobinaemia, hyperammonemia, and acute renal failure. 1

Initial Assessment and Stabilization

• Urea fertilizer ingestion can cause severe poisoning with potentially life-threatening complications including methaemoglobinaemia (18-80%), hemolysis, hyperkalemia, and acute renal failure 1, 2
• Assess for nausea, vomiting, diarrhea, and abdominal pain, which are common initial symptoms of urea herbicide poisoning 1
• Monitor vital signs with particular attention to hemodynamic stability, as hyperkalemia from renal failure can cause cardiovascular instability 2
• Obtain immediate laboratory studies including:
  • Complete blood count to assess for hemolysis
  • Comprehensive metabolic panel to evaluate renal function and electrolytes
  • Methemoglobin levels
  • Arterial blood gas analysis 1, 2

Primary Treatment Interventions

Hemodialysis

• Emergent hemodialysis is the cornerstone of treatment for significant urea fertilizer ingestion 2
• Indications for immediate hemodialysis include:
  • Hemodynamic instability due to hyperkalemia
  • Acute renal failure
  • Severe metabolic acidosis
  • Significant methaemoglobinaemia not responding to methylene blue 2
• Continuous renal replacement therapy (CRRT) may be considered for hemodynamically unstable patients who cannot tolerate conventional hemodialysis 3

Management of Methaemoglobinaemia

• Administer methylthioninium chloride (methylene blue) 1-2 mg/kg intravenously over 5-10 minutes if:
  • Patient has symptoms consistent with methaemoglobinaemia (cyanosis unresponsive to oxygen, chocolate-brown colored blood)
  • Methaemoglobin concentration >30% 1
• Monitor response to methylene blue and repeat dose if necessary 1

Supportive Care Measures

• Gastrointestinal decontamination:

  • Consider activated charcoal administration if patient presents within 1 hour of ingestion 1
  • Gastric lavage may be performed in cases of massive ingestion if the airway is protected 1

• Fluid management:

  • Administer intravenous fluids to maintain adequate hydration and promote diuresis 2
  • Monitor fluid status carefully to avoid fluid overload in patients with developing renal failure 2

• Electrolyte correction:

  • Treat hyperkalemia according to standard protocols (calcium gluconate, insulin with glucose, sodium bicarbonate, potassium-binding resins) 2
  • Monitor and correct other electrolyte abnormalities as needed 2

Monitoring and Follow-up

• Continuous cardiac monitoring for arrhythmias related to electrolyte disturbances 2
• Serial laboratory tests to monitor:
  • Renal function
  • Electrolytes
  • Methemoglobin levels
  • Complete blood count for hemolysis 1, 2
• Monitor for clinical improvement, which typically occurs within 4-5 days with appropriate treatment 2

Special Considerations

• Patients with G6PD deficiency may have increased risk of hemolysis and reduced response to methylene blue treatment 1
• Pregnant patients require special attention as urea can cross the placental barrier 4
• Pediatric patients may be more susceptible to toxicity due to their lower body mass and should be treated aggressively 1

Pitfalls to Avoid

• Delay in initiating hemodialysis can result in increased morbidity and mortality 2
• Failure to recognize and treat methaemoglobinaemia promptly can lead to tissue hypoxia and death 1
• Underestimating the severity of poisoning based solely on initial presentation, as symptoms may progress rapidly 5, 6
• Inadequate monitoring of electrolytes and renal function during treatment 2