What is the course and management of paraquat poisoning?

Management of Paraquat Poisoning

Paraquat poisoning requires immediate aggressive decontamination, strict oxygen restriction (target SpO2 85-88%), and early consultation with poison control, though prognosis remains extremely poor despite all interventions.

Immediate Actions and Decontamination

Contact poison control immediately (1-800-222-1222 in US) for expert toxicology guidance, as this is a highly lethal poisoning requiring specialized management 1.

Exposure Management

• Remove all contaminated clothing and jewelry immediately to prevent continued dermal absorption 1
• Healthcare workers must wear appropriate personal protective equipment including gloves and protective clothing when handling the patient or contaminated materials 1
• Thoroughly wash exposed skin with soap and water 2

Gastrointestinal Decontamination

• Do NOT perform gastric lavage as it is contraindicated and may worsen outcomes 3
• Administer activated charcoal (30g) and montmorillonite powder (Fuller's earth, 30-60g) orally as soon as possible to minimize further absorption 4, 3, 5
• Consider sequential gastrointestinal lavage with polyethylene glycol electrolyte solution for 5 days, which has been shown to shorten laxative time, reduce organ damage, and lower mortality compared to conventional treatment 5
• Repeat activated charcoal and adsorbent therapy daily for up to 5 days 5

Critical Oxygen Management

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

• Administer oxygen ONLY if SpO2 falls below 85% 1
• Target oxygen saturation is 85-88%, significantly lower than typical critical care targets 1
• Reduce or stop oxygen if SpO2 rises above 88% 1
• Rationale: Supplemental oxygen dramatically worsens paraquat toxicity by enhancing free radical generation and accelerating pulmonary fibrosis 1, 3
• Avoid high-concentration oxygen therapy unless the patient is severely hypoxemic 1

Elimination Enhancement

Extracorporeal Therapy

• Hemoperfusion with coated activated charcoal is the most effective method to eliminate paraquat from blood and tissue 6, 7
• Perform "continuous hemoperfusion" approximately 8 hours per day for 2-3 weeks 6
• Initiate as early as possible (ideally within 4-6 hours of ingestion) for any chance of benefit 6, 7
• Important caveat: Hemoperfusion is unlikely to change clinical course if initiated after paraquat has already distributed into tissues (>12-24 hours), as paraquat is rapidly absorbed and distributed 3, 6
• Hemodialysis alone is less effective than hemoperfusion 3

Pharmacologic Management

Immunosuppression

• High-dose corticosteroids (dexamethasone or methylprednisolone) combined with cyclophosphamide are widely practiced 3, 5
• Evidence is very weak for efficacy, but this remains standard practice in most centers managing paraquat poisoning 3

Antioxidant Therapy

• Acetylcysteine (300 mg/kg/day continuous infusion for 3 weeks) may limit systemic toxicity through free radical scavenging 4, 3
• Deferoxamine (100 mg/kg over 24 hours) has shown potential benefit in case reports when combined with acetylcysteine 4
• Salicylate may provide benefit through anti-inflammatory and NF-κB inhibitory actions 3
• Evidence limitation: No published randomized controlled trials exist for antioxidant therapy, only case reports and theoretical mechanisms 3

Supportive Care

Airway and Cardiovascular Management

• Provide standard airway management if respiratory distress develops 1
• Treat hypotension and dysrhythmias according to standard advanced life support protocols 1
• Administer benzodiazepines for seizures or severe agitation if they occur 1

Monitoring

• Maintain continuous contact with poison control for evolving treatment recommendations 1
• Monitor plasma paraquat concentrations if available (initial level >0.5 μg/mL at 4 hours predicts poor prognosis) 7
• Proudfoot's curve provides prognostic guidance based on plasma concentration and time since ingestion 7
• Monitor for acute kidney injury (typically develops 3-4 days post-ingestion), hepatotoxicity, and progressive pulmonary fibrosis 7, 5

Clinical Course and Prognosis

Organ Toxicity Timeline

• Gastrointestinal: Immediate caustic injury to oral mucosa, esophagus, and stomach 3
• Renal failure: Typically develops 2-4 days post-ingestion, may be reversible with adequate fluid support 4, 7
• Hepatotoxicity: Mild to moderate elevation of transaminases within first week 4, 5
• Pulmonary fibrosis: Progressive development over 1-3 weeks, leading to refractory hypoxemia and respiratory failure 4, 3

Prognostic Factors

• Time to treatment and plasma paraquat concentration are the primary determinants of survival 7
• Case fatality remains extremely high (often >50-90%) in all centers despite variations in treatment 3
• Survival is possible with very early aggressive treatment, but permanent pulmonary impairment (reduced CO transfer factor) may persist for months to years 4

Critical Pitfalls to Avoid

• Do NOT delay treatment waiting for confirmation of paraquat poisoning; treat based on clinical presentation and history 1
• Do NOT use liberal oxygen therapy as in typical respiratory failure—this is the single most important management difference 1
• Do NOT induce vomiting as this delays definitive care and may worsen caustic injury 2
• Do NOT rely on immunosuppression or antioxidants alone—these are adjunctive therapies only 3
• Do NOT delay hemoperfusion if available and patient presents within 12-24 hours 6