Carbamates

Exposure

  • Carbamate Insecticides
    • Carbaryl
    • Aldicarb
    • Baygon
    • Ficam
    • Propoxur
    • Ambenonium

Physiology

  • Absorption
    • Skin
    • Lungs
    • GI tract
    • Injection
  • Reversible Acteylcholinesterase Inhibition: accumulation of ACh at nicotinic and muscarinic synapses
  • Metabolism: rapid elimination by serum cholinesterases and hepatic metabolism
    • Duration of toxicity is therefore, generally shorter and less severe than with organophosphates

Diagnosis

  • ABG: metabolic acidosis, respiratory acidosis
  • FOB: may be necessary to rule out airway injury
  • CXR/Chest CT Patterns
    • Low Lung Volumes:
    • Aspiration Pneumonia: may be seen in some cases
  • PFT’s: restriction
  • Plasma Cholinesterase Activity: usually have normal activity, since carbamate inhibition is rapidly reversible
  • RBC Cholinesterase Activity: usually have normal activity, since carbamate inhibition is rapidly reversible
  • Urine Tox Screen: may detect these agents

Clinical Presentations

Acute Carbamate Exposure

(effects occur 30 min-2 hrs after exposure)

Muscarinic Effects

  • Neuro Manifestations
    • Blurred Vision
    • Miosis
  • GI/GU Manifestations
    • Nausea/Vomiting
    • Crampy Abdominal Pain (see Abdominal Pain, [[Abdominal Pain]])
    • Urinary/Fecal Incontinence
    • Urinary Frequency
    • Hypersalivation
  • Pulmonary Manifestations
  • Cardiac Manifestations
  • Other Manifestations
    • Hyperhidrosis
    • Lacrimation

Nicotinic Effects

  • Neuro Manifestations
    • Twitching/Fasciculations: fasciculations are strongly suggestive of cholinergic intoxication
    • Weakness
    • Ataxia
    • Areflexia
  • Pulmonary Manifestations
  • Cardiac Manifestations

CNS Effects

  • Anxiety/Agitation
  • Tremor
  • Seizures (see Seizures, [[Seizures]])
  • Altered Mental Status/Coma (see Coma, [[Coma]])

Treatment

  • Remove Contaminated Clothing/Wash Skin (with soap and water)/Evacuate from Site of Exposure: to prevent further contact
  • GI Decontamination: indicated for ingestions
    • Charcoal: indicated for ingestions
  • Atropine (muscarinic receptor antagonist): give 0.5-2.0 mg IV q15-20 min until clinical effect by mucosal drying and decreased secretions (some cases require multiple doses or a drip for a period of days)
    • Heart rate and pupillary size should not be used as endpoints
    • Less effective for CNS effects
    • Ineffective for nicotinic effects
  • Pralidoxime (2-PAM)
    • Reactivates cholinesterases
    • Effective for nicotinic effects
    • Dosage: give 1-2 g IV over 15-20 min
    • Pralidoxime is less effective for CNS effects
    • Probably should not be used for Carbaryl intoxication
    • If used for other carbamates, should be used only in conjunction with atropine
  • Steroids: may be beneficial in ALI, but unproven

Prognosis

  • Most cases recover within 24-48 hrs
  • Death: may occur (primarily due to respiratory failure)

References

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