Epidemiology
- Paraquat is a widely-used and toxic herbicide
- Used widely to spray marijuana fields (however, there is not believed to be a risk of illness with smoking paraquat-sprayed marijuana)
Exposure
- Accidental or Intentional Ingestion: most deaths occur due to suicide attempts (few in USA though)
- Transdermal Skin Exposure: through pesticide spraying
- Requires either soaking of the skin or contact with skin breached by injury (burn, wounds, etc)
Physiology
- Unique Superoxide Radical-Mediated Pulmonary Fibrosis
- Does not cause immediate caustic irritant injury to the lung
- Mechanism of injury may be partly iron-dependent
- Due to oxidant-related mechanism: supplemental oxygen (and radiation therapy) exacerbate the degree of injury
- Interestingly, the related pesticide Diquat does not manifest pulmonary toxicity
Diagnosis
- Blood/Urine Paraquat Level: may reveal diagnosis (although history is usually the best)
- May have a role in predicting survival
Clinical Manifestations
Cardiovascular Manifestations
Endocrinologic Manifestations
Gastrointestinal/Hepatic Manifestations
Neurologic Manifestations
Pulmonary Manifestations
- Acute Lung Injury-ARDS (see Acute Lung Injury-ARDS, [[Acute Lung Injury-ARDS]])
- Diagnosis
- Pathology: diffuse alveolar damage
- Clinical: usually occurs within 24-48 hrs of ingestion
- Subsequent Pulmonary Fibrosis (see Interstitial Lung Disease-Etiology, [[Interstitial Lung Disease-Etiology]])
- Diagnosis
- PFT’s: restriction with decreased DLCO
- ABG: hypoxemia
- Clinical
- Progresses after initial ingestion, resulting in death from respiratory failure within days-weeks
- Survivors may manifest modest and slow improvement in lung function
Renal Manifestations
Toxicologic Manifestations
Treatment
- Supplemental Oxygen/XRT: may worsen outcome
- Hemodialysis: useful
- Charcoal Hemoperfusion(see Hemoperfusion, [[Hemoperfusion]]): may provide better clearance than hemodialysis, but its benefit is unproven
- Steroids + Cyclophosphamide: single trial demonstrated mortality benefit in moderate-severe ingestions
Prognosis
- May be predicted by paraquat level
- Death from multi-organ failure typically occurs within 1-2 wks (but may occur up to 6 wks later)
References
- Winchester JF. Active methods for detoxification. In: Haddad LM, Shannon MW, Winchester JF, eds. Clinical management of poisoning and drug overdose. Third edition. Philadelphia: WB Saunders; 1997, 175-188
- Winchester JF. Paraquat and the bipyridyl herbacides. In: Haddad LM, Shannon MW, Winchester JF, eds. Clinical management of poisoning and drug overdose. Third edition. Philadelphia: WB Saunders; 1997, 845-853
- Am J Resp Crit Care Med 1999; 159:357-360