What is the treatment for organo phosphorus poisoning?

Treatment of Organophosphorus Poisoning

The treatment of organophosphorus poisoning requires immediate administration of atropine, pralidoxime, and benzodiazepines, along with supportive care including decontamination, airway management, and close monitoring for at least 48-72 hours. 1

Initial Management

• Ensure proper personal protective equipment (PPE) when caring for patients with organophosphate exposure to prevent contamination of healthcare providers 1
• Perform immediate dermal decontamination by removing contaminated clothing and copious irrigation with soap and water for external exposure 1
• Secure airway, breathing, and circulation as the first priority in management 1
• Administer atropine immediately at 1-2 mg IV for adults (0.02-0.1 mg/kg for children), doubling the dose every 5 minutes until bronchorrhea, bronchospasm, and bradycardia resolve 1
• Consider early endotracheal intubation for life-threatening organophosphate poisoning, as observational data suggests better outcomes with early intervention 1
• Avoid neuromuscular blockers metabolized by cholinesterase (succinylcholine and mivacurium) as they may cause prolonged paralysis 1, 2

Specific Antidotal Therapy

Atropine Administration

• Initial dose: 1-2 mg IV for adults (0.02-0.1 mg/kg for children), doubling every 5 minutes until atropinization (inhibition of secretions) 1
• Maintain some degree of atropinization for at least 48 hours and until depressed blood cholinesterase activity is reversed 2
• Consider atropine infusion for maintenance of atropinization 1

Pralidoxime (Oxime) Therapy

• Administer pralidoxime early to reactivate acetylcholinesterase enzyme (Class 2a recommendation, Level A evidence) 1
• Initial adult dose: 1-2 g IV administered slowly over 15-30 minutes, preferably as an infusion in 100 mL of normal saline 2
• If infusion is not practical or pulmonary edema is present, give slowly over not less than 5 minutes as a 50 mg/mL solution 2
• A second dose of 1-2 g may be given after about one hour if muscle weakness has not been relieved 2
• Maintenance therapy: 400-600 mg/hour for adults or 10-20 mg/kg/hour for children 1
• Continue pralidoxime therapy as long as signs of poisoning recur, effectively "titrating" the patient 2
• Pralidoxime is most effective when administered early, before "aging" of the phosphorylated enzyme occurs 1, 3

Benzodiazepine Administration

• Administer benzodiazepines such as diazepam or midazolam to treat seizures and agitation 1
• Benzodiazepines also help facilitate mechanical ventilation if needed 1

Monitoring and Follow-up

• Keep the patient under observation for at least 48 to 72 hours, as relapses can occur 1, 2
• Monitor for delayed muscle weakness, which can follow the initial cholinergic crisis even as late as 4 days after acute exposure 1
• Watch for complications such as myonecrosis, rhabdomyolysis, and renal damage 1
• Continue to assess cholinesterase activity when available to guide therapy duration 3

Advanced and Adjunctive Therapies

• Consider sodium bicarbonate infusion to produce mild to moderate alkalinization, which has shown effectiveness in recent investigations 4
• Intravenous magnesium sulfate may decrease hospitalization duration and improve outcomes 4
• Bio-scavengers including fresh frozen plasma or albumin may be useful through clearing of free organophosphates 4
• Hemofiltration and antioxidants have also been suggested for organophosphorus poisoning 4

Special Considerations

• Organophosphates form a covalent bond with acetylcholinesterase causing permanent inactivation ("aging"), while carbamates spontaneously dissociate 1
• Pralidoxime should not be withheld when the class of poison (organophosphate vs. carbamate) is unknown 1
• Treatment is most effective if initiated immediately after poisoning 2
• When poison has been ingested, consider the likelihood of continuing absorption from the lower bowel, which constitutes new exposure and can cause fatal relapses after initial improvement 2

Common Pitfalls and Caveats

• Underdosing of atropine is common - remember to double the dose every 5 minutes until atropinization is achieved 1
• Avoid using morphine, theophylline, aminophylline, reserpine, and phenothiazine-type tranquilizers in patients with organophosphate poisoning 2
• Do not delay pralidoxime administration - it is most effective when given early before aging of the enzyme-inhibitor complex 3
• The case fatality rate for organophosphorus poisoning is generally more than 15%, emphasizing the need for prompt and aggressive treatment 5