Organophosphate Poisoning

OVERVIEW

• common cause of poisoning in the developing world
• covalent bonding with inactivation of acetylcholinesterase
• results in cholinergic crisis

CLINICAL FEATURES

Risk factors

• insecticides/fertilisers
• surface and room sprays
• baits for cockroaches
• shampoos against head lice
• pet preparations
• crop protection and livestock dipping
• fumigation
• nerve agents (sarin)

Clinical features (cholinergic syndrome)

• DUMBBELS: diarrhoea, urination, miosis, bronchorhea, bradycardia, emesis, lacrimation, salivation
• SLUDGE: salivation, lacrimation, urination, defaecation, emesis

INVESTIGATIONS

• butyrylcholinesterase or acetylcholinesterase activity

MANAGEMENT

Resuscitation

• aspiration/bronchospasm/seizures may necessitate airway protection and mechanical ventilation
• haemodynamic monitoring and management with the below agents
• remove contaiminated clothes -> wash

Acid-base and Electrolytes

Specific Therapy

• atropine: 0.02mg/kg boluses -> recurrent boluses q5min doubling the dose each time, treats bradycardia, hypotension and excess secretion production
• pralidoxime chloride 30mg/kg IV -> 8mg/kg/hr: muscle weakness
• benzodiazepines: midazolam 0.2mg/kg, seizures or agitation
• activated charcoal if presents with 1-2 hours

Underlying Cause

• psychiatric assessment
• work place health and safety review

References and Links

• Abedin MJ, Sayeed AA, Basher A, Maude RJ, Hoque G, Faiz MA. Open-label randomized clinical trial of atropine bolus injection versus incremental boluses plus infusion for organophosphate poisoning in Bangladesh. J Med Toxicol. 2012 Jun;8(2):108-17. PMC3550249.
• Buckley NA, Eddleston M, Li Y, Bevan M, Robertson J. Oximes for acute organophosphate pesticide poisoning. Cochrane Database Syst Rev. 2011 Feb 16;(2):CD005085. PMID: 21328273.
• Eddleston M, Dawson A, Karalliedde L, Dissanayake W, Hittarage A, Azher S, Buckley NA. Early management after self-poisoning with an organophosphorus or carbamate pesticide – a treatment protocol for junior doctors. Crit Care. 2004 Dec;8(6):R391-7. PMC1065055.
• Eddleston M, Buckley NA, Eyer P, Dawson AH. Management of acute organophosphorus pesticide poisoning. Lancet. 2008 Feb 16;371(9612):597-607. PMC2493390.
• Gussow L. Toxicology Rounds: Atropine Dosing Regimen Suboptimal for Organophosphate Poisoning. Emergency Medicine News. 2013; 35(5)p8 [Free Full Text]