Organophosphate/carbamate poisoning Flashcards
What are organophosphates and carbamates?
common insecticides that inhibit cholinesterase activity, causing acute muscarinic manifestations and some nicotinic symptoms
What are 9 acute muscarinic manifestations of organophosphate/carbamate poisoning?
- Salivation
- Lacrimation
- Urination
- Diarrhoea
- Emesis
- Bronchorrhoea
- Bronchospasm
- Bradycardia
- Miosis
What are 2 examples of nicotinic symptoms that can arise due to organophosphate/carbamate poisoning?
- Muscle fasciculations
- Weakness
After what time period can neuropathy develop from organophosphate/carbamate poisoning?
days to weeks after exposure
How is a diagnosis of organophosphate/carbamate poisoning usually made?
clinical diagnosis
What are 2 tests that can be performed in the workup of organophosphate/carbamate poisoning?
- Trial of atropine
- Measurement of red blood cell acetylcholinesterase level
What is the treatment of bronchorrhoea and bronchospasm in organophosphate/carbamate poisoning?
titrated high-dose atropine
How can neuromuscular toxicity in organophosphate/carbamate poisoning be treated?
IV pralidoxime
What is the difference between organophosphates and carbamates?
different structurally but both inhibit cholinesterase activity
What are organophosphate/carbamates sometimes used for clinically? 2 examples
- to reverse neuromuscular blockage e.g. neostigmine, pyridostigmine, edrophonium
- or to treat glaucoma - echothiopate
- treat Alzheimer’s disease - tacrine and donepezil
What are 2 examples of carbamates most commonly implicated in human poisoning?
- Aldicarb
- Methomyl
What are 6 examples of organophosphates most often implicated in human poisoning?
- Chlorpyrifos
- Diazinon
- Dursban
- Fenthion
- Malathion
- Parathion
How can organophosphates/carbamates be absorbed?
through GI tract, lungs, skin
What is the pathophysiology of how organophosphates/carbamates cause poisoning?
they inhibit plasma and RBC cholinesterase, preventing breakdown of acetylcholine which then accumulates in synapses
What is the difference in how carbamates vs organophosphates act/are cleared?
- Carbamates are cleared spontaneously within 48h after exposure
- Organophosphates can irreversibly bind to cholinesterase
What are 9 possible acute features of organophosphate/carbamate poisoning?
- Acute muscarinic cholinergic toxidrome
- Acute nictoinic cholinergic toxidrome
- Muscle fasciculations
- Weakness
- Respiratory findings: rhonchi, wheezing, hypoxia
- Bradycardia
- CNS toxicity - seizures, excitability, lethargy, coma
- Pancreatitis
- Arrhythmias e.g. heart block, QTc interval prolongation
What are 10 features of cholinergic muscarinic syndromes?
- Salivation
- Lacrimation
- Urination
- Defecation/diarrhoea
- GI cramps
- Emesis
- Bronchorrhoea, wheezing
- Bronchoconstriction
- Bradycardia
- Miosis
What are 9 features of cholinergic nicotinic syndromes?
- Mydriasis (dilation of pupil)
- Tachycardia
- Weakness
- Hypertension
- Hyperglycaemia
- Fasciculations
- Sweating
- Abdominal pain
- Paresis
What can occur as a delayed symptomology following organophosphate/carbamate poisoning?
- Weakness of proximal, cranial, respiratory muscles which may develop 1-3 days after exposure
- Some organophosphates may cause axonal neuropathy beginning 1-3 weeks after exposure
How long may it take for weakness to develop following organophosphate/carbamate poisoning?
1-3 days (and 1-3 weeks for axonal neuropathy)
How long is it usually before symptoms of weakness after organophosphate/carbamate poisoning may resolve?
2-3 weeks
What are 2 possible long-term, persistent sequelae of organophosphate poisoning?
- Cognitive deficits
- Parkinsonism
What is the basis of the diagnosis for organophosphate/carbamate poisoning? 5 key things
clinical diagnosis:
- muscarinic toxidrome
- with prominent respiratory findings,
- pinpoint pupils,
- muscle fasciculations
- and weakness
What test can be performed if clinical findings are equivocal when diagnosing organophosphate/carbamate poisoning?
reversal or abatement of muscarinic symptoms after 1mg of atropine (0.01-0.02 mg/kg in children) supports the diagnosis
What characteristic odours may be present following organophosphate/carbamate poisoning?
many organophosphates have garlic-like or petroleum odours
What investigation can be peroformed to indicate the severity of poisoning and monitor effectiveness of treatment?
RBC cholinesterase activity
What is the primary marker of effectiveness of treatment for organophosphate/carbamate poisoning?
patient response
What are the 4 key aspects of treatment for organophosphate/carbamate poisoning?
- Supportive therapy
- Atropine for respiratory manifestations
- Decontamination
- Pralidoxime for neuromuscular manifestations
What should patients be admitted and monitored for following organophosphate/carbamate poisoning?
should be closely monitored for respiratory failure due to weakness of respiratory muscles
must be admitted for supportive therapy - key
What is atropine given to treat in organophosphate/carbamate poisoning?
given in amounts sufficient to relieve bronchospasm and bronchorrhoea
What dosage and route of atropine is given?
initially 2-5 mg IV (0.05 mg/kg in children)
dose can be doubled every 3-5 minutes as needed
grams may be necessary for severely poisoned patients
When should decontamination be performed in organophosphate/carbamate poisoning?
should be pursued as soon as possible after stabilisation
What is important to avoid while providing care to patients with organophosphate/carbamate poisoning?
self-contamination
How is decontamination performed for patients being treated for organophosphate/carbamate poisoning?
- if topical exposure: clothes are removed, body surface flushed thoroughly
- for ingestion within 1hr of presentation, activated charcoal can be used (gastric emptying usually avoided - if done, trachea intubated before to prevent aspiration)
When is pralidoxime given for organophosphate/carbamate poisoning and why?
after atropine has been given, to relieve neuromuscular symptoms
What dosing and route is pralidoxime given in organophosphate/carbamate poisoning?
- 1-2g in adults, 20-40mg/kg in children
- bolus given over 15-30 minutes IV after exposure to an organophosphate or carbamate
- after bolus, infusion can be used: 8mg/kg/h in adults, 10-20 mg/kg/h in children
What medication can be used to treat any seizures due to organophosphate/carbamate poisoning?
benzodiazepines e.g. prophylactic diazepam to prevent neurocognitive sequelae
What are 2 treatments available for out-of-hospital exposure to organophosphates/carbamates?
- Low doses of atropine using commercially prepared autoinjectors (2mg for adults)
- Autoinjection of 10mg diazepam for people exposed to a chemical attack
To summarise, what is the key clinical presentation of organophosphate/carbamate toxicity?
muscarinic cholinergic toxidrome with prominent respiratory and neuromuscular findings
