What are the complications and management of paraquat poisoning?

Management of Paraquat Poisoning: Complications and Treatment

Paraquat poisoning requires immediate consultation with a poison center or toxicologist, with early decontamination and restricted oxygen therapy (target saturation 85-88%) as critical interventions to improve survival. 1

Pathophysiology and Complications

Paraquat is a highly toxic herbicide that causes multi-organ damage through generation of reactive oxygen species. Major complications include:

Acute Phase (Hours to Days)

• Gastrointestinal effects: Caustic burns in upper digestive tract, vomiting 1, 2
• Respiratory distress: Early pulmonary edema progressing to ARDS 2
• Renal damage: Non-oliguric acute renal failure 1, 2
• Hepatic injury: Cytolytic hepatitis, elevated liver enzymes 3, 4
• Circulatory failure: Shock in severe cases 4, 5

Delayed Phase (Days to Weeks)

• Progressive pulmonary fibrosis: Leading to refractory hypoxemia 4, 5
• Multi-organ failure: Involving lungs, kidneys, liver 2

Management Algorithm

1. Immediate Interventions (0-4 hours)

• Decontamination:

  • Remove contaminated clothing and perform copious irrigation with soap and water 3, 1
  • Gastric lavage if within 1-2 hours of ingestion
  • Activated charcoal administration (as much as possible, as quickly as possible) 6
  • Use appropriate personal protective equipment (gloves) to prevent secondary exposure 3, 1

• Oxygen Management:

  • Restrict supplemental oxygen (target saturation 85-88%)
  • Only provide oxygen when saturation falls below 85% 3, 1
  • Excessive oxygen worsens lung injury through enhanced free radical production 3

2. Early Treatment (4-24 hours)

• Extracorporeal Removal:

  • Hemoperfusion with activated charcoal within first 2-4 hours of ingestion 1, 6
  • Consider "continuous hemoperfusion" (8 hours/day for 2-3 weeks in severe cases) 6

• Fluid Management:

  • Provide fluid resuscitation to maintain adequate renal perfusion 1
  • Monitor for non-oliguric renal failure 1, 4

3. Ongoing Management (24+ hours)

• Immunosuppressive Therapy:

  • Cyclophosphamide and methylprednisolone pulse therapy 1, 7
  • This combination may be life-saving despite limited evidence 1

• Antioxidant Therapy:

  • N-acetylcysteine (300 mg/kg/day for up to 3 weeks) 1, 4
  • Consider deferoxamine (100 mg/kg in 24 hours) 4

• Organ Support:

  • Manage renal failure with appropriate fluid management and dialysis if needed 1, 2
  • Avoid mechanical ventilation with high oxygen concentrations when possible 3, 1
  • Monitor and treat hepatic dysfunction 3, 4

Prognostic Indicators

• Poor Prognosis Factors:
  • Ingestion (vs. inhalation or skin exposure) 5
  • Amount ingested (>35-50 mg/kg associated with mortality) 5
  • Empty stomach at time of ingestion 5
  • Presence of caustic gastric lesions on endoscopy 5
  • Development of renal failure 5
  • High plasma paraquat concentrations within first 24 hours 5

Special Considerations

• Avoid neuromuscular blockers metabolized by cholinesterase 3
• Early intubation may be necessary for airway protection, but use caution with oxygen settings 3
• Pediatric patients should follow similar protocols with appropriate dose adjustments 1

Monitoring

• Plasma paraquat concentrations (if available)
• Renal function tests
• Liver function tests
• Pulmonary function (CO transfer factor)
• Oxygen saturation (maintain between 85-88%)

Paraquat poisoning has high mortality, with survival rates heavily dependent on amount ingested and time to treatment. Early recognition, immediate decontamination, restricted oxygen therapy, and aggressive antioxidant/immunosuppressive treatment offer the best chance for survival.