38-49: Paraquat Poisoning

Paraquat is used as an herbicide. Concentrated solutions of paraquat are highly corrosive to the oropharynx, esophagus, and stomach. The fatal dose after absorption may be as small as 4 mg/kg. If ingestion of paraquat is not rapidly fatal because of its corrosive effects, the herbicide may cause progressive pulmonary fibrosis, with death ensuing after 2–3 weeks. Patients with plasma paraquat levels above 2 mg/L at 6 hours or 0.2 mg/L at 24 hours are likely to die.

TREATMENT

Remove ingested paraquat by immediate induced emesis, or by gastric lavage if the patient is already in a health care facility. Clay (bentonite or fuller's earth) and activated charcoal are effective adsorbents. Administer repeated doses of 60 g of activated charcoal by gastric tube every 2 hours for at least three or four doses. Charcoal hemoperfusion, 8 hours per day for 2–3 weeks, has been anecdotally reported to be lifesaving, but clinical and animal studies are equivocal. Supplemental oxygen should be withheld unless the PaO₂ is less than 70 mm Hg because oxygen may contribute to the pulmonary damage, which is mediated through lipid peroxidation. Immunosuppressive therapy (cyclophosphamide with dexamethasone) has shown possible benefit in anecdotal reports.