Paraquat toxicity: Difference between revisions
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==Background==
==Background==
Paraquat is an herbicide that has a rapid and large distribution and can be fatal even with small ingestions. It has a high case-fatality rate (>50%)<ref>Gawaramanna I, Buckley N. Medical management of paraquat ingestion. Br J Clin Pharmacol. 2011;72(5):745–757</ref> which makes it a frequent means of suicide in the developing world, as well as a dangerous accidental occupational exposure.
*Paraquat is an herbicide that has a rapid and large distribution and can be fatal even with small ingestions. It has a high case-fatality rate (>50%)<ref>Gawaramanna I, Buckley N. Medical management of paraquat ingestion. Br J Clin Pharmacol. 2011;72(5):745–757</ref> which makes it a frequent means of suicide in the developing world, as well as a dangerous accidental occupational exposure.
 
*Paraquat exerts its toxic effects via multiple proposed mechanisms, including lipid peroxidation and generation of reactive oxygen species, direct mitochondrial toxicity, and apoptosis.
Paraquat exerts its toxic effects via multiple proposed mechanisms, including lipid peroxidation and generation of reactive oxygen species, direct mitochondrial toxicity, and apoptosis.


==Clinical Features==
==Clinical Features==
[[File:Paraquat tongue.jpg|thumb|Paraquat Tongue (Credit: wikitox.org)]]
[[File:Paraquat tongue.jpg|thumb|Paraquat Tongue (Credit: wikitox.org)]]


Overall, pulmonary and renal toxicities predominate and are the primary cause of mortality. GI toxicity is nearly universal and is probably an underrecognized cause of mortality secondary to erosion and perforation.  
Overall, pulmonary and renal toxicities predominate and are the primary cause of mortality. GI toxicity is nearly universal and is probably an under-recognized cause of mortality secondary to erosion and perforation.  


*Gastrointestinal: predominate early  
*Gastrointestinal: predominate early  
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==Differential Diagnosis==
==Differential Diagnosis==
===Toxic Ingestion===
*[https://wikem.org/wiki/Caustic_ingestion Caustic Ingestion]
*[https://wikem.org/wiki/Toxic_alcohols Toxic Alcohols]
*[https://wikem.org/wiki/Ingested_foreign_body Foreign Body Ingestion]


===Oral [[Burns]]/Mucositis===
*[https://wikem.org/wiki/Burns Burns]
*Infectious Causes
**[[Aphthous stomatitis|Aphthous Ulcer
**[[Herpes simplex]] infection
**[[Coxsackie virus]]
**Tonsillitis
**[[methotrexate toxicity|Methotrexate]]/chemotherapy toxicity
===Acute Dyspnea===
{{SOB DDX}}


==Evaluation==
==Evaluation==
===Workup===
*Labs
**CBC
**BMP
**[[LFTs]] and coagulation tests
**[[VBG]] or [[ABG]]
**[[UA]]: high concentrations of paraquat in the urine will cause it to appear blue
**Urine dithionate test:
***Add 1cc of 1% sodium dithionate (hematology labs have this solution) to 10mL urine
***Blue color change indicates presence of paraquat
*Imaging
**[[CXR]]
**[[EKG]]
**consider CT if stable to evaluate for perforation/[[mediastinitis]]


===Diagnosis===
*Based on urine test


==Management==
==Management==
''Patients who present in extremis after an ingestion will not survive regardless of management and should be treated palliatively. Large >50mL ingestions of paraquat are universally fatal. Aggressive resuscitation is futile. ''
===Resuscitation===
*Airway: consider early aggressive [[intubation]] for any respiratory distress or large (>100mL) ingestions
*Breathing: [[CXR]], [[O2]]
**Avoid aggressive oxygen therapy unless severe [[hypoxia]] due to increased free radical production
*Circulation: may develop early shock and require aggressive [[pressors|inotropic]] support
===Decontamination===
*Paraquat is absorbed transdermally. Unprotected first responders and healthcare workers are at risk
*Remove clothing and wash patient's skin if spillage or obvious skin involvement present
*Consider [[activated charcoal]] or Fuller's Earth if within 1-2 hrs of ingestion
*Consider [[NG tube]] for administration of [[activated charcoal]]
**Must weigh risks as NGT placement can exacerbate caustic injury
===Supportive Care===
*IV fluids: patients often 2-3L fluid down
*Pain control


===Antidotes/Additional Therapies===
*Some centers administer [[glucocorticoids]] (typically [[dexamethasone]] 6mg-10mg IV q6h)
*Consider [[NAC]], vitamin C, other free radical scavengers in consultation with toxicologist or poison control
*No role for extracorporeal elimination ([[hemodialysis/Hemoperfusion]], CRRT)


==Disposition==
==Disposition==
 
*If small/trivial exposure and patient asymptomatic at 6 hours, unlikely to manifest a significant toxicity
*Any symptomatic exposure requires admission for close hemodynamic monitoring and supportive care


==See Also==
==See Also==
 
*[[Toxicology (main)]]


==External Links==
==External Links==

Latest revision as of 00:22, 22 October 2020

Background

  • Paraquat is an herbicide that has a rapid and large distribution and can be fatal even with small ingestions. It has a high case-fatality rate (>50%)[1] which makes it a frequent means of suicide in the developing world, as well as a dangerous accidental occupational exposure.
  • Paraquat exerts its toxic effects via multiple proposed mechanisms, including lipid peroxidation and generation of reactive oxygen species, direct mitochondrial toxicity, and apoptosis.

Clinical Features

Paraquat Tongue (Credit: wikitox.org)

Overall, pulmonary and renal toxicities predominate and are the primary cause of mortality. GI toxicity is nearly universal and is probably an under-recognized cause of mortality secondary to erosion and perforation.

Differential Diagnosis

Toxic Ingestion

Oral Burns/Mucositis

Acute Dyspnea

Acute dyspnea

Emergent

Non-Emergent

Evaluation

Workup

  • Labs
    • CBC
    • BMP
    • LFTs and coagulation tests
    • VBG or ABG
    • UA: high concentrations of paraquat in the urine will cause it to appear blue
    • Urine dithionate test:
      • Add 1cc of 1% sodium dithionate (hematology labs have this solution) to 10mL urine
      • Blue color change indicates presence of paraquat
  • Imaging

Diagnosis

  • Based on urine test

Management

Patients who present in extremis after an ingestion will not survive regardless of management and should be treated palliatively. Large >50mL ingestions of paraquat are universally fatal. Aggressive resuscitation is futile.

Resuscitation

  • Airway: consider early aggressive intubation for any respiratory distress or large (>100mL) ingestions
  • Breathing: CXR, O2
    • Avoid aggressive oxygen therapy unless severe hypoxia due to increased free radical production
  • Circulation: may develop early shock and require aggressive inotropic support

Decontamination

  • Paraquat is absorbed transdermally. Unprotected first responders and healthcare workers are at risk
  • Remove clothing and wash patient's skin if spillage or obvious skin involvement present
  • Consider activated charcoal or Fuller's Earth if within 1-2 hrs of ingestion
  • Consider NG tube for administration of activated charcoal
    • Must weigh risks as NGT placement can exacerbate caustic injury

Supportive Care

  • IV fluids: patients often 2-3L fluid down
  • Pain control

Antidotes/Additional Therapies

Disposition

  • If small/trivial exposure and patient asymptomatic at 6 hours, unlikely to manifest a significant toxicity
  • Any symptomatic exposure requires admission for close hemodynamic monitoring and supportive care

See Also

External Links

References

  1. ↑ Gawaramanna I, Buckley N. Medical management of paraquat ingestion. Br J Clin Pharmacol. 2011;72(5):745–757
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