1.57 CME

Empoisonnement au paraquat

Conférencier: Dr Ranjith Ravella

Consultant en médecine interne à l'hôpital KHIMS, Khammam

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Description

Paraquat poisoning is a medical emergency resulting from exposure to paraquat, a potent and highly toxic herbicide commonly used in agriculture. The poison can enter the body through ingestion, inhalation, or skin contact, and even small amounts can be lethal. Once absorbed, paraquat generates reactive oxygen species that cause extensive cellular damage, particularly in the lungs, liver, and kidneys. Initial symptoms of paraquat poisoning include severe abdominal pain, nausea, vomiting, and diarrhea, often with blood. As the condition progresses, it leads to respiratory distress, acute kidney injury, liver failure, and potentially fatal pulmonary fibrosis. Inhalation can cause severe lung damage, while skin contact may lead to burns and systemic toxicity if not promptly treated.Diagnosis is primarily based on the history of exposure and clinical symptoms, supported by laboratory tests that detect paraquat in blood or urine. Unfortunately, there is no specific antidote for paraquat poisoning. Treatment focuses on reducing further absorption of the toxin—typically through gastric lavage, activated charcoal, or Fuller's earth—and supportive care to manage symptoms and complications. This may include oxygen therapy, dialysis for kidney failure, and other intensive care measures.Due to its extreme toxicity and the lack of effective treatments, paraquat use is highly restricted and banned in many countries. In regions where it is still used, strict safety protocols are enforced to minimize the risk of exposure.

Résumé

  • The speaker emphasizes the high fatality rate associated with paraquat poisoning, attributing it to its toxicity and the absence of effective treatments. Paraquat, a non-selective contact herbicide, is popular in developing countries due to its rapid action on weeds, despite being banned in some regions. Key characteristics include its broad-spectrum effectiveness, rapid action, and partial inactivation upon soil contact.
  • The speaker elucidates the mechanisms of paraquat toxicity, primarily involving the generation of superoxide anions and the oxidation of cellular NADPH. The speaker mentioned that Paraquat accumulates in cells, undergoing redox cycling, leading to oxidative stress, cell damage, and a secondary inflammatory response, targeting organs like the lungs, kidneys, and liver.
  • Regarding organ involvement, the presentation highlighted the impact on the lungs, leading to acute alveolitis and pulmonary fibrosis. Kidney involvement begins quickly with the development of large vaculation in the proximal converted tubule, while liver congestion and hepatoellar injury occur within hours to days. Consuming 30ml or more of 20 to 24% paraquat is often lethal.
  • The speaker then describes the different classifications of paraquat poisoning based on symptomatology. The speaker emphasizes the importance of physical examination, including inspecting the mouth and fairings for signs of necrosis and ulceration and being cautious of oxygen administration unless hypoxia is confirmed with saturation rates below 90%.
  • Diagnostic measures include a complete blood picture, renal function tests, chest X-ray, and ECG. Assessing kidney function is essential, with elevated creatinine levels suggesting severe poisoning. Arterial blood gas analysis is also crucial, with academia and lactic acidosis indicating poor prognosis. Urine paraquat levels serve as a qualitative confirmation of exposure, with darker colors indicating higher concentrations and worse outcomes.
  • Medical management strategies focus on decontamination through activated charcoal or fuller's earth, and initiating hemoperfusion or hemodialysis, ideally within 4 hours of injection. Anti-inflammatory and antioxidant therapies, including high-dose gluocorticoids, N-acetylcysteine, vitamin E, and vitamin C, might offer slight benefits.
  • The presenter discussed case studies, noting that the most susceptible age group is between 17-35, where the gender ratio of male vs female is 4:1. Complications include acute kidney injury and ARDS. Early recognition, compound removal, gastric lavage, and oxygen restriction are all emphasized.

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