Paraquat Toxicity: Clinical Manifestations and Emergency Management
Clinical Manifestations
Paraquat poisoning causes multi-organ toxicity with pulmonary fibrosis being the primary cause of death, typically occurring within 2 days to several weeks depending on the dose ingested. 1
Immediate Toxic Effects
- Caustic burns of the oropharynx, esophagus, and gastrointestinal tract develop rapidly after ingestion, with the absence of these burns indicating better prognosis 1
- Acute renal failure occurs in the majority of patients who eventually die, though isolated renal failure alone may not indicate fatal outcome 1, 2
- Hepatic injury manifests as elevated liver enzymes and can occur alongside other organ damage 3, 2
- Cardiovascular collapse and shock may develop in severe exposures 4
Progressive Pulmonary Toxicity
- Diffuse alveolitis followed by extensive pulmonary fibrosis is the hallmark of paraquat toxicity, caused by free radical formation, lipid peroxidation, and NADPH depletion in lung tissue 1
- Acute respiratory distress syndrome (ARDS) develops as the toxin actively accumulates in lung tissue against a concentration gradient 4, 2
- Refractory hypoxemia progresses as pulmonary fibrosis advances 3
Prognostic Indicators
- Plasma paraquat concentration is the most important prognostic indicator, directly correlating with the quantity absorbed 1
- Ingestion of ≥50 mg/kg is typically fatal within 2 days, while lower doses may cause delayed death over several weeks 1
- Presence of caustic burns in the upper digestive tract indicates poor prognosis 1
Emergency Management Algorithm
Phase 1: Immediate Safety and Decontamination (First 15 minutes)
Remove all contaminated clothing and jewelry immediately, then thoroughly wash all exposed skin with soap and water to prevent continued dermal absorption. 5, 6, 7
- Healthcare workers must wear gloves and protective clothing when handling the patient or contaminated materials to prevent secondary exposure 6, 7
- Use warmed shower water at lower pressure in pediatric patients to prevent hypothermia and additional skin damage 5
Phase 2: Contact Poison Control (Immediately)
Contact the national poison control center (1-800-222-1222 in the United States) as soon as paraquat exposure is identified for expert guidance and maintain continuous contact for evolving recommendations. 5, 6, 7
- Do not administer any oral agents (including decontamination solutions or antidotes) unless specifically directed by poison control specialists 5
Phase 3: Airway Protection and Hemodynamic Stabilization (Priority Before Decontamination)
Secure the airway and achieve hemodynamic stabilization before attempting any gastrointestinal decontamination, as aspiration risk is significant. 5, 7
- Provide standard airway management if respiratory distress develops 6, 7
- Treat hypotension and dysrhythmias according to standard protocols 6, 7
- Administer benzodiazepines for seizures or severe agitation if they occur 6
Phase 4: Gastrointestinal Decontamination (Only After Airway Protection)
Consider multiple-dose activated charcoal (15-20g every 6 hours) only after securing the airway and achieving hemodynamic stability, as activated charcoal is preferred over gastric lavage. 5, 7
- The American College of Medical Toxicology recommends against routine gastric lavage for paraquat poisoning 5
- Activated charcoal or Fuller's earth work through adsorption and are preferred decontamination agents over mechanical gastric lavage 5, 1
Phase 5: Critical Oxygen Management (Unique to Paraquat)
Avoid supplemental oxygen unless SpO2 falls below 85%, and reduce or stop oxygen if saturation rises above 88%, as oxygen dramatically worsens paraquat toxicity through increased free radical production. 5, 6, 7
- Target oxygen saturation of 85-88%, significantly lower than typical critical care targets 6, 7
- Oxygen accelerates paraquat-induced lung injury by increasing free radical production and lipid peroxidation 5, 7, 1
- This is the most critical pitfall to avoid in paraquat management, as liberal oxygen administration is uniquely harmful 5, 6
Phase 6: Supportive Care and Monitoring
Provide supportive care focused on correction of metabolic derangements while monitoring for multi-organ failure. 7
- Monitor renal function closely, as acute renal failure decreases paraquat excretion and worsens prognosis 1, 2
- Assess for caustic burns in the oropharynx and upper GI tract as prognostic indicators 1
Common Pitfalls to Avoid
- Do not delay airway protection to perform gastrointestinal decontamination 5
- Do not provide supplemental oxygen liberally – this is uniquely harmful in paraquat toxicity and represents the most dangerous error in management 5, 6
- Do not use gastric lavage routinely when activated charcoal is the evidence-based alternative 5
- Do not administer oral agents without poison control guidance 5
Treatment Efficacy Note
Treatment of paraquat poisoning remains largely ineffective despite various attempted interventions. 1 Hemodialysis, hemoperfusion, forced dialysis, superoxide dismutase, glutathione peroxidase, N-acetylcysteine, and other free radical scavengers have failed to clearly improve survival rates in clinical practice, though one case report suggested potential benefit from early antioxidant therapy combining deferoxamine and acetylcysteine. 1, 3 The extremely poor prognosis persists even with optimal management, particularly with ingestions above lethal doses. 8, 2