Paraquat PoisoningParaquat ( Gramoxone) is the most toxic herbicide knownIt is a dipyridyl compoundOne of the most widely used herbicideBright green in colour with pungent smellKilling green plants tissue on contactAvailable in liquid form in various strengthBecome biologically inactive upon contact with soilPure paraquat highly toxic if ingestedAlso highly toxic by inhalationModerately toxic by dermal routeCan cause moderate to severe eye irritation

Toxic Dose Of Paraquat< 20 mg/kg results in vomiting & diarrhoea20 -50 mg/kg results in pharyngeal burns, vomiting, diarrhoea, acute kidney & liver insufficiency & necrosis of liver> 50 mg/kg results in death in 72 hours because of multiple organ failureLD50 for human is 30 mg/kg or equivalent to a few ml of concentrated paraquat

Pathophysiology Of ParaquatCytotoxic oxygen radicals generatedSelectively accumulates in the lungsLungs major target organAlso Liver, Kidneys, Heart & CNSAbsorption : skin GIT Respiratory Tract

Clinical Toxicity Of ParaquatDirect Local ToxicityGI Tract- result from the caustic properties of paraquatWithin a few minutes to hours a burning sensation in the buccal cavityWithin 1 2 daysulceration of the lips, tongue & pharynx esophageal perforationSkin - skin rashesLungs hemoptysisEyes corneal ulceration & scarring

Clinical Toxicity Of ParaquatSystemic Toxicity- result from oral ingestionBuccal and / or esophageal ulcerationRenal failure ( within 2-6 days)Metabolic acidosisPulmonary edema (24-48 hr after ingestion)Respiratory distress syndrome (1st week after ingestion)Death usually occurs within 1 2 weeks, but maybe observed up to 6 weeks after ingestion

DiagnosisUrine paraquat concentration of 1mg/ml or abovePlasma paraquat levels Fatal outcomes: plasma levels >0.2mg/ml at 24 hour after ingestion or 0.1mg/ml at 48 hour

Management Of Paraquat PoisoningEnsure Airway, Breathing & Circulation are intactControl vomiting with 1. Ondansetron 8mg (5mg/sq.m in children) by slow IV infusion over 15 minutes 2. ProchlorperazineAdminister either1. Activated charcoal 100g for adults or 2g/kg BW for children2. Fullers earth 15% solution: 1L for adults or 15mg/kg in childrenGastric lavage - performed cautiously in view of possible ulceration of pharynx & esophagus

Management Of Paraquat Poisoning - continuePurgativee.g. Mannitol or Magnesium Sulphate Polyethylene glycol solution for bowel irrigationRehydrate- to renal clearance of paraquat- paying attention for fluid overload & electrolyte imbalanceAnalgesics- for severe pain from oral, esophageal or abdominal corrosive injuryHemoperfusion within 12 hour of poisoning to reduce mortality > hemodialysis - Up to 2-3 weeks after an ingestion