Organophosphate toxicity
How is OP toxicity medically managed?
- Airway control and oxygenation - Intubation may be needed in cases of respiratory distress - Immediate aggressive atropine use - Central line and arterial lines needed for multi-medications and blood gases - Monitoring of vitals and pulse oximetry - ECG - IV magnesium sulfate has been proven to help
How might someone present clinically with organophosphate poisoning?
Muscarinic effects (DUMBELS): - Diaphoresis and diarrhoea - Urination (incontinence) - Miosis and blurred vision - Bradycardia and bronchospasm - Emesis (vomiting) and excess lacrimation - Salivation Nicotinic effects: - Muscle fasciculations - Cramping - Weakness - Diaphragmatic failure CNS effects: - Anxiety - Emotional lability - Restlessness - Confusion - Ataxia, tremors, seizures - Coma
What is the pathophysiology of organophosphates?
Primary mechanism: inhibition of carboxyl ester hydrolases, particularly AChE - a CNS and PNS co-transmitter than assists in breaking down ACh in the NMJ This inhibition of AChE leads to an accumulation of ACh throughout the nervous system, resulting in overstimulation of muscarinic and nicotinic receptors
Paralysis also may result from organophosphate poisoning. What are the three types?
T1 - Acute paralysis secondary to continued depolarisation at the NMJ T2 - Intermediate syndrome (occurring after the resolution of acute OP poisoning symptoms) T3 - OP-induced delayed polyneuropathy (2-3 weeks after exposure)
How can organophosphates be absorbed?
Cutaneously, ingested, inhaled or injected
What factors can be considered diagnostic for poor prognosis?
- High 6 hr post admission blood lactate levels - Low blood pH - Low post admission 6 hr lactate clearance rates
What are the key medications needed in the treatment of OP toxicity?
1. Atropine 2. Pralidoxime (antidote) 3. Diazepam (facilitates inhibitory GABA neurotransmission)
How is OP toxicity confirmed?
Based on the measurement of cholinesterase activity, usually via RBC cholinesterase - representing the RBC membranes found in neuronal tissue, therefore it accurately reflects the nervous system OP AChE inhibition
What additional clinical tests could also be performed?
CXR - pulmonary oedema ECG - prolonged QT interval, elevated ST segments, inverted T waves (sinus tachycardia)
What are organophosphates?
Chemicals/pesticides/nerve agents that are used in the workplace and in domestic situations, that often cause intoxication or can be lethal
What are the types of organophosphates?
Insecticides Nerve gases Opthalmic agents Herbicides Antihelmintics