Paraquat Poisoning

Yesterday afternoon, I came across a case of paraquat poisoning by a 14-year old Indian boy in the ward. He was brought to A&E the previous night and on enquiry, claimed that he drank 1 gulp of weed killer after scolded by his mother. In the ward, he was given:

• activated charcoal 25 g 4 hourly
• fuller's earth 60 g hourly [consists of hydrated aluminium silicates]
  
• 3 pint normal saline & 2 pint dextrose 5% over 24 hours [to promote diuresis]
  

The patient's urine was tested postive for paraquat, hence he and his parents have been informed of his prognosis-Dead in List =(

I guess most of you are aware of the the recent tragedy that struck a Malaysian family (the mother gave drinks laced with paraquat to her 4 children before drinking it her herself). From conversations with other healthcare professionals, it is found out that paraquat poisoning is very common among the Indian community in the estate due to its availability and possibly, their ignorance of the serious implication (most suicidal attempts were impulsive, and they didn't really mean to end their lives). I have googled paraquat poisoning and here are some of my findings:


What is Paraquat
Paraquat is used to prepare land for planting or control weeds in major food crops. It is highly poisonous to humans, but becomes inactive upon adsorption with clay in soil or water.

In the United States, paraquat is classified as "restricted use," which means that it can be used only by licensed applicators. In the European Union, paraquat has been forbidden since July 2007. However, it is readily available in Malaysia and other developing countries.

Due to its toxicity, the form of it that is marketed in the United States has a blue dye to keep it from being confused with beverages such as coffee, a sharp odour to serve as a warning, and an added agent to cause vomiting if someone drinks it. If only the paraquats marketed in Malaysia have these safeguards added.


Clinical Manifestations of Paraquat Poisoning
Major acute effects- ulceration of skin, lips, tongue, pharynx and oesophagus
Acute systemic effects- pulmonary oedema, cardiac, renal or hepatic failure and convulsions

After a person ingests a large amount of paraquat, he or she is likely to immediately have pain and swelling of the mouth and throat. The next signs of illness following ingestion are gastrointestinal (digestive tract) symptoms, such as nausea, vomiting, abdominal pain, and diarrhoea (which may become bloody).

Following ingestion of greater than 50ml of the liquid concentrate, the patient may develop pulmonary oedema, cardiac failure, renal failure, liver failure and also convulsions caused by central nervous system involvement. Under these circumstances, death may occur within several hours to a few days as a result of multiple organ failure.

Ingestion of a smaller volume (10 ml to 20 ml) of the concentrate produces the same symptoms with the exception that the development of renal failure occurs within 2-6 days after ingestion.

Mechanism of Paraquat Poisoning
In the lungs, the paraquat ion undergoes a continuous redox process to form free radicals capable of reacting with oxygen. This reaction leads to the production of a reactive oxygen also known as superoxide anion and the regeneration of the paraquat ions. Subsequently, these ions may react to form the highly reactive hydroxyl radical, which is thought to be responsible for lipid peroxidation and cell death.

As oxygen exacerbates the destruction of lung tissues, supplemental oxygen should not be given as an initial measure. Oxygen is recommended only if fraction of inspired oxygen (FiO2) falls below 50%.


Management
Sadly, there is no clinically proven antidote for paraquat poisonining and treatment is generally supportive.

• Prevention of absorption

Gastric lavage should be performed immediately, if possible within 2 hours after ingesting paraquat (reduce further absorption of paraquat into the bloodstream.)

Following gastric emptying, the administration of mineral absorbents such as Fuller's Earth or activated charcoal is initiated to remove any unabsorbed paraquat remaining in the gastrointestinal tract.

In some cases, cathartics, for example magnesium sulphate, magnesium citrate or sorbitol, may be given every 4 hours either concurrently or separately with the absorbents.

• Enhancement of elimination

The recommended regimen for increased paraquat excretion from the blood is haemoperfusion, which has been shown to increase the chance of survival among poisoned patients. Using this approach, the haemoperfusion may be repeated until the paraquat level remains below a certain value, normally 0.01 mg/ml.



Interesting Facts (But Efficacy Not Proven)
In a study involving 375 patients, intensive antioxidant therapy (N-acetylcysteine, glutathione, vitamin C) was given in the hope that it may scavenge oxidants. Only 29.3% patients survived.

Some groups advocate routine use of antioxidants (Vitamin C 4000 mg/day and Vitamin E 250 mg/day) even though their efficacy is unproven.

Pulse therapy using steroids (methylprednisolone or dexamethasone) and cyclophosphamide has been shown to be effective in preventing pulmonary fibrosis by some authors and not so by others.

Food for thoughts:

There are actually some anti-paraquat lobby groups in overseas!

Perhaps our government should have tighter regulations on paraquat usage? (like in the States)

In view of the intentional suicidal attempts with paraquat, education to the public on paraquat is important as some people may not know that it is that fatal.

I wonder what the child was thinking when the doctor told him about his condition. When I saw him at the ward, he seemed fine emotionally, but I wouldn't know what was going through in his mind. Sad case indeed =(

Have you come across any paraquat poisoning at your hospital or klinik kesihatan? Do share with us the management practised there.

References:

Centers for Disease Control and Prevention; Available from: URL: http://www.bt.cdc.gov/agent/paraquat/basics/facts.asp

Dr. Mohd. Isa Abdul Majid. Know your pesticides: paraquat. Available from: URL: http://www.prn2.usm.my/mainsite/bulletin/sun/1997/sun13.html

BMJ Group Blogs. Louise Kenny on paraquat poisoning. Available from: URL: http://blogs.bmj.com/bmj/2009/11/12/louise-kenny-on-paraquat-poisoning

Sandhu JS et al. Outcome on paraquat poisoning-a five year study. Indian J Nephrol 2003;13: 64-68. Available from: URL: http://www.asiatox.org/6th%20APAMT%20pdf/Therapeutic%20approach%20to%20paraquat%20poisoning..pdf

Hong S-Y. Therapeutic approach to paraquat poisoning. Available from: URL: http://medind.nic.in/iav/t03/i2/iavt03i2p64.pdf