Exposure

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

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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

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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

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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
  • Cough
  • Dyspnea
  • Bronchospasm (see Obstructive Lung Disease, [[Obstructive Lung Disease]])
  • Bronchorrhea:
  • Acute Lung Injury-ARDS (see Acute Lung Injury-ARDS, [[Acute Lung Injury-ARDS]])
• Cardiac Manifestations
  • Bradycardia/Conduction Defects (see Bradycardia, [[Bradycardia]] and Heart Blocks, [[Heart Blocks]])
  • Hypotension (see Hypotension, [[Hypotension]])
• Other Manifestations
  • Hyperhidrosis
  • Lacrimation

Nicotinic Effects

• Neuro Manifestations
  • Twitching/Fasciculations: fasciculations are strongly suggestive of cholinergic intoxication
  • Weakness
  • Ataxia
  • Areflexia
• Pulmonary Manifestations
  • Decreased Central Respiratory Drive + Respiratory Muscle Weakness: may lead to respiratory failure
    • Acute/Chronic Hypoventilation (see Acute Hypoventilation, [[Acute Hypoventilation]] and Chronic Hypoventilation, [[Chronic Hypoventilation]])
  • Laryngospasm (see Obstructive Lung Disease, [[Obstructive Lung Disease]])
  • Bronchospasm (see Obstructive Lung Disease, [[Obstructive Lung Disease]])
• Cardiac Manifestations
  • Tachycardia (see Tachycardia, [[Tachycardia]])
  • Hypertenson (see Hypertension, [[Hypertension]])

CNS Effects

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

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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

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Prognosis

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

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References

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