Carbamate toxicity

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Background

Clinical Features

Autonomic Nervous System Receptors and Their Effects

  • Parasympathetic - ACh is transm
    • Muscarinic
      • receptors in heart, eye, lung, GI, skin and sweat glands
      • Bradycardia
      • Miosis
      • Bronchorrhea / Bronchospasm
      • Hyperperistalsis (SLUDGE)
      • Sweating
      • Vasodilation
    • Nicotinic
  • Sympathetic
    • Alpha effects (vessels, eye, skin)
    • Beta effects (heart, lungs)
  • Symptoms caused by acetylcholine buildup in CNS and PNS.
  • CNS symptoms = headache, confusion, vertigo, seizures, coma
  • Muscarinic Receptors
    • SLUDGE(M) = Salivation, Lacrimation, Urination, Diarrhea, GI pain, Emesis, Miosis
  • Nicotinic Receptors (NMJ)
    • MTWThF = Mydriasis/Muscle cramps, Tachycardia, Weakness, Twitching, Hypertension/Hyperglycemia, Fasiculations
  • Common causes of death in organophosphate toxicity
    • Killers B's = Bradycardia, Bronchorrhea, Bronchospasm

Differential Diagnosis

SLUDGE Syndrome

Weakness

Chemical weapons

Symptomatic bradycardia

Evaluation

Management

  • Pralidoxime not useful with carbamates but should be given unless organophosphate toxicity completely ruled out

Decontamination

  • Providers should wear appropriate PPE during decontamination.
    • Neoprene or nitrile gloves and gown (latex and vinyl are ineffective)
  • Dispose of all clothes in biohazard container
  • Wash patient with soap and water

Supportive Care

  • IVF, O2, Monitor
  • Aggressive airway management is of utmost importance.
    • Intubation often needed due to significant respiratory secretions / bronchospasm.
    • Use nondepolarizing agent (Rocuronium or Vecuronium)
    • Succinylcholine is absolutely contraindicated
  • Benzodiazepines for seizures

Antidotes

  • Dosing with atropine and pralidoxime are time dependent and provides ability to reverse symptoms while awaiting agent metabolism
  • For exposure to nerve agents, manufactured IM autoinjectors are available for rapid administration:
    • Mark 1
      • Contains 2 separate cartridges: atropine 2 mg + 2-PAM 600 mg
      • Being phased out with newer kits
    • DuoDote
      • Single autoinjector containing both medications
      • Same doses as Mark 1: atropine 2 mg + 2-PAM 600 mg

Antidotes

Atropine

  • First-line antidote — muscarinic antagonist; treats bronchorrhea, bronchospasm, bradycardia, and secretions[3]
  • Does NOT reverse nicotinic symptoms (weakness, fasciculations, paralysis)
  • Starting dose: 1-2 mg IV (pediatric: 0.02-0.05 mg/kg, minimum 0.1 mg)
  • Doubling protocol: If inadequate response after 5 minutes, double the dose (1 → 2 → 4 → 8 → 16 mg...) until atropinization is achieved[3]
  • Massive doses may be required — total doses of 100+ mg in the first 24 hours have been reported[4]
  • Endpoints of adequate atropinization (goal of therapy):
    • Drying of bronchial secretions (most important endpoint)
    • Heart rate >80 bpm
    • Systolic BP >80 mmHg
  • Do NOT target: Fully dilated pupils, absent bowel sounds, or HR >150 — these indicate atropine toxicity[5]
  • After initial atropinization: Consider atropine infusion (10-20% of loading dose per hour) to maintain effect
  • Optimize oxygenation before giving atropine to reduce risk of dysrhythmias (though in resource-limited settings, do not withhold atropine waiting for oxygen)[4]


Pralidoxime

  • AKA 2-PAM
  • Oxime that reactivates phosphorylated AChE → primarily reverses nicotinic symptoms (weakness, fasciculations, respiratory muscle paralysis)[6]
  • Must give atropine BEFORE pralidoxime to prevent worsening of muscarinic symptoms
  • Must be given before aging occurs (see aging table above)
  • Adult dose: 1-2 g IV over 15-30 minutes, may repeat in 1 hour; or 30 mg/kg bolus then 8-10 mg/kg/hr continuous infusion[3]
  • Pediatric dose: 20-50 mg/kg IV, then 5-10 mg/kg/hr infusion
  • Continue until clinical improvement or patient is off ventilator
  • Controversies:
    • Evidence for benefit of pralidoxime is inconsistent; several meta-analyses have not shown clear mortality benefit when added to atropine[7]
    • However, per AHA 2023 guidelines and expert consensus, oximes should still be given for significant OP poisoning, particularly when fasciculations, weakness, or paralysis are present[3]
    • Efficacy depends on timing (before aging), dose, and the specific OP compound involved
  • Caution: Administer slowly — rapid IV push can cause hypertensive crisis, cardiac arrest

Disposition

  • Admit all patients with respiratory or CNS compromise and all who require atropine


See Also

External Links

References

  1. ↑ Silberman J, Taylor A. Carbamate Toxicity. [Updated 2019 Jun 18]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK482183/
  2. ↑ https://www.merckmanuals.com/professional/injuries-poisoning/poisoning/organophosphate-poisoning-and-carbamate-poisoning
  3. ↑ 3.0 3.1 3.2 3.3 Cite error: Invalid <ref> tag; no text was provided for refs named medscape
  4. ↑ 4.0 4.1 Cite error: Invalid <ref> tag; no text was provided for refs named bmj
  5. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named wfsa
  6. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named pralidoxime_statpearls
  7. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named prognosis
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