What is the emergency management of acute paraquat ingestion?

Emergency Management of Acute Paraquat Ingestion

Immediate Priorities: Rescuer Safety and Decontamination

Paraquat is a corrosive chemical requiring immediate protective measures for healthcare providers before any patient contact. Wear gloves and protective equipment when handling the patient's clothes or body fluids, especially vomit, as paraquat can be absorbed through the rescuer's skin or respiratory tract 1.

Gastric Decontamination (Within First 1-2 Hours)

• Perform gastric lavage immediately if the patient presents within 1-2 hours of ingestion 2. This is one of the few situations where early gastric lavage may be beneficial, as paraquat is rapidly absorbed and highly lethal.

• Administer Fuller's earth (1 g/kg) or activated charcoal (1 g/kg) via nasogastric tube as soon as possible to prevent further absorption 3, 4. Fuller's earth is preferred if available, but activated charcoal is an acceptable alternative 3.

• Repeat doses of adsorbent every 2-4 hours for the first 12-24 hours to interrupt enterohepatic circulation 2.

Critical Prognostic Assessment

The plasma paraquat concentration is the single most important prognostic indicator and must be obtained immediately 3, 5. Use Proudfoot's curve to predict survival: plasma levels >2 μg/mL at 4 hours or >0.9 μg/mL at 6 hours predict near-certain mortality 5.

Additional poor prognostic indicators include:

• Ingestion of >40 mg/kg body weight (acute fulminant poisoning with multi-organ failure and death within hours to days) 2
• Ingestion of 20-40 mg/kg (moderate-severe poisoning with delayed death at 2-3 weeks from pulmonary fibrosis) 2
• Presence of caustic burns in the mouth, throat, or esophagus indicates significant ingestion 3
• Urine paraquat test positivity (4+) indicates substantial systemic absorption 5

Extracorporeal Elimination (First 24 Hours)

Initiate charcoal hemoperfusion immediately, ideally within 4 hours of ingestion, as this is the most effective elimination method 5, 4. Perform at least one session, though multiple sessions may be considered in the first 24 hours 5.

• Hemodialysis can be added if hemoperfusion is unavailable, though it is less effective 3, 4.
• Continue elimination procedures even if plasma levels suggest poor prognosis, as occasional survivors have been reported 4.

Supportive Care and Antioxidant Therapy

Oxygen Management - Critical Pitfall

Avoid supplemental oxygen unless absolutely necessary for life-threatening hypoxemia (SpO2 <85-90%) 3. Paraquat toxicity is mediated by free radical formation in the lungs, and oxygen accelerates this process through redox cycling 3, 6. Use the minimum FiO2 necessary to maintain marginal oxygenation.

Antioxidant Regimen

Consider early administration of antioxidants, though evidence is limited:

• N-acetylcysteine: 300 mg/kg/day continuous infusion for 3 weeks 4
• Deferoxamine: 100 mg/kg over 24 hours 4
• These agents showed potential benefit in one survival case with massive ingestion, though clinical validation remains insufficient 3, 4

Organ-Specific Monitoring

• Renal function: Monitor creatinine and urine output closely; acute kidney injury typically develops 2-4 days post-ingestion and may be reversible with aggressive fluid resuscitation 5, 6
• Pulmonary function: Serial chest X-rays and monitoring for dyspnea; pulmonary fibrosis may not manifest for days to weeks 3, 2
• Hepatic function: Monitor transaminases for hepatotoxicity 5, 4

Contraindications and Ineffective Therapies

• Do not induce vomiting or administer ipecac - this is contraindicated and may cause aspiration 1, 7
• Do not give water or milk for dilution - no proven benefit and may cause emesis 1, 8
• Immunosuppressive therapy, superoxide dismutase, and glutathione peroxidase have failed to improve outcomes 3
• Forced diuresis has not shown clear benefit 3

Disposition and Prognosis

All patients with confirmed paraquat ingestion require ICU admission regardless of initial symptoms 5, 6. Patients may appear well initially but deteriorate rapidly over hours to days 2.

• Ingestion <20 mg/kg: Full recovery expected with gastrointestinal symptoms only 2
• Ingestion 20-40 mg/kg: Majority fatal from pulmonary fibrosis at 2-3 weeks 2
• Ingestion >40 mg/kg: Death within hours to days from multi-organ failure 2

Obtain psychiatric evaluation for all intentional ingestions before discharge 7.

The overall mortality from significant paraquat poisoning remains extremely high despite all interventions, with death occurring from either early multi-organ failure or delayed progressive pulmonary fibrosis 3, 6, 2.