What is the treatment for urea poisoning?

Treatment of Urea Poisoning

For urea herbicide poisoning, treatment is primarily supportive with symptomatic management, and methylene blue (methylthioninium chloride) 1-2 mg/kg IV over 5-10 minutes should be administered if methaemoglobinaemia exceeds 30% or symptoms consistent with methaemoglobinaemia are present. 1

Initial Assessment and Stabilization

• Assess for life-threatening complications including altered mental status, respiratory distress, hemodynamic instability, and signs of methaemoglobinaemia (cyanosis, dyspnea, altered consciousness) 1
• Obtain immediate laboratory studies including complete blood count, methaemoglobin level, arterial blood gas, electrolytes, and renal function 1
• Secure airway and provide supplemental oxygen to maintain saturation >95%, particularly if methaemoglobinaemia is suspected 1

Specific Antidote Therapy

• Administer methylene blue 1-2 mg/kg intravenously over 5-10 minutes when methaemoglobin concentration exceeds 30% or when symptoms consistent with methaemoglobinaemia are present, regardless of measured levels 1
• The dose of methylene blue depends on severity of clinical features rather than a fixed protocol 1
• Monitor for response to methylene blue and consider repeat dosing if methaemoglobinaemia persists or recurs 1

Supportive Care Measures

• Provide aggressive supportive care including intravenous fluid resuscitation with balanced crystalloid solutions to maintain adequate urine output and renal perfusion 1
• Manage gastrointestinal symptoms (nausea, vomiting, diarrhea, abdominal pain) with antiemetics and fluid replacement as these are the primary manifestations of urea herbicide toxicity 1
• Monitor for hemolysis as urea herbicides are metabolized to aniline derivatives which can cause both methaemoglobinaemia and hemolytic anemia 1

Role of Extracorporeal Treatment

• Hemodialysis is NOT indicated for urea herbicide poisoning as the primary toxicity (methaemoglobinaemia) is managed with methylene blue, and supportive care is generally adequate 1
• Intermittent hemodialysis should be reserved for cases with severe acute kidney injury or refractory metabolic acidosis, though this is uncommon in urea herbicide poisoning 2, 3

Monitoring and Follow-up

• Serial methaemoglobin levels should be obtained every 2-4 hours until levels normalize and clinical improvement is sustained 1
• Monitor renal function as urea herbicides can potentially cause kidney injury, though this is rare 1
• Assess for delayed hemolysis with serial hemoglobin measurements over 24-48 hours 1

Critical Pitfalls to Avoid

• Do not delay methylene blue administration while waiting for methaemoglobin levels if clinical features strongly suggest methaemoglobinaemia (cyanosis unresponsive to oxygen, chocolate-brown blood) 1
• Do not confuse urea herbicide poisoning with uremia (elevated blood urea nitrogen from kidney failure), as these are entirely different conditions requiring different management 4, 5
• Do not assume normal oxygen saturation on pulse oximetry rules out methaemoglobinaemia, as pulse oximetry is unreliable in the presence of methaemoglobin and arterial blood gas co-oximetry is required 1