What is the management of paraquat poisoning?

Management of Paraquat Poisoning

Paraquat poisoning requires immediate decontamination, strict oxygen restriction (target SpO2 85-88%), and supportive care, with contact to poison control centers being essential for guidance, as no specific antidote exists and mortality remains extremely high despite aggressive treatment. 1, 2, 3

Immediate Safety and Decontamination

Healthcare Worker Protection

• Use appropriate personal protective equipment including gloves and protective clothing when handling the patient or any contaminated materials, as paraquat can cause secondary exposure through skin contact or inhalation of toxic fumes from vomit or body fluids. 1, 3

Patient Decontamination

• Remove all contaminated clothing and jewelry immediately to prevent continued dermal absorption. 1, 3
• Thoroughly wash all exposed skin areas with soap and water using copious amounts; in pediatric patients, use warmed water at lower pressure with heat lamps to prevent hypothermia. 1, 2, 3
• Consider multiple-dose activated charcoal (15-20g every 6 hours) only after securing the airway and achieving hemodynamic stability, as this is the preferred decontamination method over gastric lavage. 2, 3
• Do not perform routine gastric lavage, as activated charcoal or Fuller's earth are superior through adsorption mechanisms rather than mechanical removal. 2, 4, 5

Critical Oxygen Management - Unique to Paraquat

This is the most critical and counterintuitive aspect of paraquat management:

• Avoid supplemental oxygen unless oxygen saturation falls below 85%. 1, 2, 3
• Target oxygen saturation of 85-88%, which is dramatically lower than standard critical care targets. 1, 2, 3
• Reduce or stop oxygen therapy if saturation rises above 88%. 1, 2, 3
• Rationale: Paraquat toxicity is uniquely worsened by high oxygen concentrations because oxygen accelerates free radical production through lipid peroxidation and NADPH depletion, dramatically worsening lung injury and fibrosis. 1, 2, 3, 4, 6

Supportive Care and Monitoring

Airway and Hemodynamic Management

• Provide standard airway management if respiratory distress develops, but only after ensuring adequate decontamination measures. 1, 3
• Treat hypotension and dysrhythmias according to standard protocols. 1, 3
• Administer benzodiazepines for seizures or severe agitation if they occur. 1

Poison Control Center Consultation

• Contact poison control centers immediately for expert guidance and maintain continuous contact for evolving treatment recommendations. 1, 2, 3

Prognostic Assessment

• Plasma paraquat concentration is the most important prognostic indicator, with ingestion of 50 mg/kg typically fatal within 2 days. 4, 6
• Absence of caustic burns in the upper digestive tract indicates better prognosis. 4
• Presence of renal failure alone may not indicate fatal outcome, though it develops in the majority of patients who eventually die. 4

Treatments With Limited or No Evidence

Elimination Methods

• Hemodialysis and hemoperfusion have been attempted but show no clear improvement in survival rates, as paraquat rapidly distributes into tissues within 12-24 hours and renal excretion decreases rapidly with tubular necrosis. 4, 6, 5

Antioxidant Therapy

• Evidence for antioxidants (N-acetylcysteine, deferoxamine, superoxide dismutase) is extremely weak, with only case reports suggesting potential benefit when combined with early decontamination. 4, 7, 6

Immunosuppression

• Immunosuppression with cyclophosphamide and corticosteroids (dexamethasone, methylprednisolone) is widely practiced but evidence for efficacy is very weak, though one small case series of 9 patients treated with pulse cyclophosphamide and methylprednisolone reported 100% survival. 8, 6

Common Pitfalls to Avoid

• Never delay airway protection to perform gastrointestinal decontamination, as aspiration risk is significant. 2
• Never provide supplemental oxygen liberally - this is uniquely harmful in paraquat toxicity and represents the most common management error. 2, 3
• Never use gastric lavage routinely when activated charcoal is available and safer. 2, 6
• Never assume treatment will be effective - case fatality remains very high (often >50%) despite all interventions, and realistic prognostic discussions with families are essential. 4, 6