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AIP: Acute weakness > Organophosphate/carbamate poisoning > Flashcards

Organophosphate/carbamate poisoning Flashcards

1
Q

What are organophosphates and carbamates?

A

common insecticides that inhibit cholinesterase activity, causing acute muscarinic manifestations and some nicotinic symptoms

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2
Q

What are 9 acute muscarinic manifestations of organophosphate/carbamate poisoning?

A
  1. Salivation
  2. Lacrimation
  3. Urination
  4. Diarrhoea
  5. Emesis
  6. Bronchorrhoea
  7. Bronchospasm
  8. Bradycardia
  9. Miosis
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3
Q

What are 2 examples of nicotinic symptoms that can arise due to organophosphate/carbamate poisoning?

A
  1. Muscle fasciculations
  2. Weakness
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4
Q

After what time period can neuropathy develop from organophosphate/carbamate poisoning?

A

days to weeks after exposure

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5
Q

How is a diagnosis of organophosphate/carbamate poisoning usually made?

A

clinical diagnosis

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6
Q

What are 2 tests that can be performed in the workup of organophosphate/carbamate poisoning?

A
  1. Trial of atropine
  2. Measurement of red blood cell acetylcholinesterase level
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7
Q

What is the treatment of bronchorrhoea and bronchospasm in organophosphate/carbamate poisoning?

A

titrated high-dose atropine

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8
Q

How can neuromuscular toxicity in organophosphate/carbamate poisoning be treated?

A

IV pralidoxime

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9
Q

What is the difference between organophosphates and carbamates?

A

different structurally but both inhibit cholinesterase activity

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10
Q

What are organophosphate/carbamates sometimes used for clinically? 2 examples

A
  1. to reverse neuromuscular blockage e.g. neostigmine, pyridostigmine, edrophonium
  2. or to treat glaucoma - echothiopate
  3. treat Alzheimer’s disease - tacrine and donepezil
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11
Q

What are 2 examples of carbamates most commonly implicated in human poisoning?

A
  1. Aldicarb
  2. Methomyl
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12
Q

What are 6 examples of organophosphates most often implicated in human poisoning?

A
  1. Chlorpyrifos
  2. Diazinon
  3. Dursban
  4. Fenthion
  5. Malathion
  6. Parathion
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13
Q

How can organophosphates/carbamates be absorbed?

A

through GI tract, lungs, skin

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14
Q

What is the pathophysiology of how organophosphates/carbamates cause poisoning?

A

they inhibit plasma and RBC cholinesterase, preventing breakdown of acetylcholine which then accumulates in synapses

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15
Q

What is the difference in how carbamates vs organophosphates act/are cleared?

A
  • Carbamates are cleared spontaneously within 48h after exposure
  • Organophosphates can irreversibly bind to cholinesterase
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16
Q

What are 9 possible acute features of organophosphate/carbamate poisoning?

A
  1. Acute muscarinic cholinergic toxidrome
  2. Acute nictoinic cholinergic toxidrome
  3. Muscle fasciculations
  4. Weakness
  5. Respiratory findings: rhonchi, wheezing, hypoxia
  6. Bradycardia
  7. CNS toxicity - seizures, excitability, lethargy, coma
  8. Pancreatitis
  9. Arrhythmias e.g. heart block, QTc interval prolongation
17
Q

What are 10 features of cholinergic muscarinic syndromes?

A
  1. Salivation
  2. Lacrimation
  3. Urination
  4. Defecation/diarrhoea
  5. GI cramps
  6. Emesis
  7. Bronchorrhoea, wheezing
  8. Bronchoconstriction
  9. Bradycardia
  10. Miosis
18
Q

What are 9 features of cholinergic nicotinic syndromes?

A
  1. Mydriasis (dilation of pupil)
  2. Tachycardia
  3. Weakness
  4. Hypertension
  5. Hyperglycaemia
  6. Fasciculations
  7. Sweating
  8. Abdominal pain
  9. Paresis
19
Q

What can occur as a delayed symptomology following organophosphate/carbamate poisoning?

A
  • 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
20
Q

How long may it take for weakness to develop following organophosphate/carbamate poisoning?

A

1-3 days (and 1-3 weeks for axonal neuropathy)

21
Q

How long is it usually before symptoms of weakness after organophosphate/carbamate poisoning may resolve?

A

2-3 weeks

22
Q

What are 2 possible long-term, persistent sequelae of organophosphate poisoning?

A
  1. Cognitive deficits
  2. Parkinsonism
23
Q

What is the basis of the diagnosis for organophosphate/carbamate poisoning? 5 key things

A

clinical diagnosis:

  1. muscarinic toxidrome
  2. with prominent respiratory findings,
  3. pinpoint pupils,
  4. muscle fasciculations
  5. and weakness
24
Q

What test can be performed if clinical findings are equivocal when diagnosing organophosphate/carbamate poisoning?

A

reversal or abatement of muscarinic symptoms after 1mg of atropine (0.01-0.02 mg/kg in children) supports the diagnosis

25
Q

What characteristic odours may be present following organophosphate/carbamate poisoning?

A

many organophosphates have garlic-like or petroleum odours

26
Q

What investigation can be peroformed to indicate the severity of poisoning and monitor effectiveness of treatment?

A

RBC cholinesterase activity

27
Q

What is the primary marker of effectiveness of treatment for organophosphate/carbamate poisoning?

A

patient response

28
Q

What are the 4 key aspects of treatment for organophosphate/carbamate poisoning?

A
  1. Supportive therapy
  2. Atropine for respiratory manifestations
  3. Decontamination
  4. Pralidoxime for neuromuscular manifestations
29
Q

What should patients be admitted and monitored for following organophosphate/carbamate poisoning?

A

should be closely monitored for respiratory failure due to weakness of respiratory muscles

must be admitted for supportive therapy - key

30
Q

What is atropine given to treat in organophosphate/carbamate poisoning?

A

given in amounts sufficient to relieve bronchospasm and bronchorrhoea

31
Q

What dosage and route of atropine is given?

A

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

32
Q

When should decontamination be performed in organophosphate/carbamate poisoning?

A

should be pursued as soon as possible after stabilisation

33
Q

What is important to avoid while providing care to patients with organophosphate/carbamate poisoning?

A

self-contamination

34
Q

How is decontamination performed for patients being treated for organophosphate/carbamate poisoning?

A
  • 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)
35
Q

When is pralidoxime given for organophosphate/carbamate poisoning and why?

A

after atropine has been given, to relieve neuromuscular symptoms

36
Q

What dosing and route is pralidoxime given in organophosphate/carbamate poisoning?

A
  • 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
37
Q

What medication can be used to treat any seizures due to organophosphate/carbamate poisoning?

A

benzodiazepines e.g. prophylactic diazepam to prevent neurocognitive sequelae

38
Q

What are 2 treatments available for out-of-hospital exposure to organophosphates/carbamates?

A
  1. Low doses of atropine using commercially prepared autoinjectors (2mg for adults)
  2. Autoinjection of 10mg diazepam for people exposed to a chemical attack
39
Q

To summarise, what is the key clinical presentation of organophosphate/carbamate toxicity?

A

muscarinic cholinergic toxidrome with prominent respiratory and neuromuscular findings

AIP: Acute weakness (18 decks)

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