Chemical Weapons Poisoning, Emergency Medicine

Basics

Description

Chemical agents that affect CNS, pulmonary, cardiovascular, dermal, ocular, or GI systems when exposed to victims

Etiology

Blood agents: Cyanide:
- Inhibition of cellular respiration by binding to ferric ion in cytochrome oxidase a-a3 and uncoupling oxidative phosphorylation
Blister agents: Sulfur mustard, nitrogen mustard, lewisite, phosgene oxime:
- Alkylation and cross-linking of purine bases of DNA and amino acids resulting in change in structure of nucleic acid, proteins, and cellular membranes
Lacrimators and riot control agents: 1-chloroacetophenone (CN; Mace), o-chlorobenzylidene malononitrile (CS), oleoresin capsaicin-pepper spray (OC), chloropicrin, adamsite (DM):
- Mucous membrane irritators
Pulmonary irritants (choking agents):
- High water solubility: Ammonia:
  - Mucous membrane irritation of eyes and upper airway
- Intermediate water solubility: Chlorine:
  - Forms hydrochloric acid, hydrochlorous acids, which form free radicals causing upper airway and pulmonary irritation
- Low water solubility: Phosgene:
  - Mild irritant effects initially, then delayed pulmonary edema as late as 24 hr
  - Direct pulmonary damage after hydrolysis in lungs to hydrochloric acid
Nerve agents:
- Anticholinesterase inhibitors-causes cholinergic overstimulation at muscarinic, nicotinic, and CNS sites
Incapacitating agents: 3-quinuclidinyl benzilate (BZ):
- Anticholinergic (antimuscarinic)

Diagnosis

Signs and Symptoms

History
Multiple victims, house fire, known exposure (agent determines history findings)
Physical Exam

Blood agents (cyanide and cyanogens):
- Vital signs:
  - Tachypnea and hyperpnea (early); respiratory depression (late)
  - Hypertension and tachycardia (early); hypotension and bradycardia (late)
  - Death within seconds to minutes
- CNS:
  - Headache
  - Mental status changes
  - Seizures
- Pulmonary:
  - Dyspnea
  - Noncardiogenic pulmonary edema
  - Cyanosis uncommon
- GI:
  - Odor of bitter almonds (sometimes)
  - Burning in mouth and throat
  - Nausea, vomiting
Blister agents (mustards, lewisite):
- General:
  - Mortality, 2-4%
- Dermatologic:
  - Skin erythema, edema, pruritus can appear 2-24 hr after exposure.
  - Necrosis and vesiculation appear 2-18 hr after exposure.
- Head, eyes, ears, nose, and throat (HEENT):
  - Airway occlusion from sloughing of debris
  - Laryngospasm, sore throat, sinusitis
  - Eye pain, photophobia, lacrimation, blurred vision, blepharospasm, periorbital edema, conjunctival edema, corneal ulceration
- Pulmonary:
  - Bronchospasm, tracheobronchitis
  - Respiratory failure
  - Hacking cough
- GI:
  - Nausea, vomiting
- Hematologic:
  - Leukopenia
Lacrimators and riot control agents (tear gases):
- HEENT:
  - Eye pain
  - Lacrimation
  - Blepharospasm
  - Temporary blindness
- Dermatologic:
  - Skin irritation
  - Papulovesicular dermatitis (tear gas)
  - Superficial burns
- Pulmonary:
  - Cough
  - Chest tightness
  - Dry throat
  - Sensation of suffocation
  - Pulmonary edema when exposed to high concentrations without ventilation
Pulmonary irritants (choking agents):
- HEENT:
  - Eye pain, lacrimation, blepharospasm
  - Temporary blindness
- Dermatologic:
  - Skin irritation, dry throat, nasal irritation
- Pulmonary:
  - Shortness of breath, cough, bronchospasm
  - Chest pain
  - Pulmonary edema as late as 24 hr from exposure (phosgene)
Nerve agents (sarin, tabun, soman, VX):
- SLUDGEBAM syndrome:
  - Salivation
  - Lacrimation
  - Urination
  - Defecation
  - GI cramps
  - Emesis
  - Bronchorrhea, bronchoconstriction, bradycardia (most life threatening)
  - Abdominal upset
  - Miosis
- HEENT:
  - Miosis
  - Hypersecretion by salivary, sweat, lacrimal, and bronchial glands
- CNS:
  - Irritability, nervousness
  - Giddiness
  - Fatigue, lethargy, depression
  - Ataxia, convulsions, coma
- Pulmonary:
  - Bronchoconstriction
  - Bronchorrhea
- GI:
  - Nausea, vomiting, diarrhea
  - Crampy abdominal pains
  - Urinary and fecal incontinence
- Musculoskeletal:
  - Fasciculations, skeletal muscle twitching
  - Weakness
  - Flaccid paralysis
Incapacitating agents (BZ):
- Anticholinergic (antimuscarinic) toxidrome:
  - Hot as a hare
  - Dry as a bone
  - Red as a beet
  - Blind as a bat
  - Mad as a hatter
  - Hypertension
  - Tachycardia
  - Hyperpyrexia
  - Urinary retention
  - Decreased bowel sounds

Essential Workup

History and symptoms key to type of agent exposure
Physical exam:
- Cyanide (bitter almonds, comatose, hypotensive, metabolic acidosis)
- Mustard (faint, sweet odor of mustard or garlic, blisters, sloughing of skin, dyspnea)
- Check for SLUDGEBAM syndrome.
- Lacrimators (eye irritation, lacrimation, blepharospasm)
- Choking agents (dyspnea, bronchospasm)

Diagnosis Tests & Interpretation

Lab

Arterial blood gases:
- Cyanide:
  - Decreased atrioventricular (AV) oxygen saturation gap
  - Lactic acidemia with high anion gap metabolic acidosis
  - Arterialization of venous blood
  - Cyanide levels cannot be performed in clinically relevant timeframe.
CBC:
- Leukopenia, thrombocytopenia, anemia with significant mustard exposure
Electrolytes, BUN, creatinine, glucose
Urinalysis
Creatine phosphokinase (CPK)
Lactate for cyanide
Erythrocyte cholinesterase activity for nerve agents

Imaging
CXR for pulmonary edema

Differential Diagnosis

Asthma/COPD
Stevens-Johnson syndrome
Toxic epidermal necrolysis
Pemphigus vulgaris
Scalded skin syndrome
Organophosphate or carbamate pesticide poisoning
Botulism
Radiation poisoning
CHF
Anaphylactoid reaction

Treatment

Pre-Hospital

Avoid contamination of environment and clinicians:
- Use level A or level B personal protective equipment.
- Decontamination:
  - Dermal wet decontamination primarily for nerve and blistering agents
  - Dry decontamination (removal of clothing and jewelry) for other agents
Administer atropine even if patient is tachycardic because condition may result from hypoxia.

Initial Stabilization/Therapy

ABCs
Patient decontamination:
- Brush off powder from chemical.
- Irrigate skin and eyes with copious amounts of water or saline.
- Remove and dispose of clothing in double bags.
Protection for health care workers:
- Level A or B personal protective suit
- Chemical-resistant suit
- Heavy rubber gloves and boots, neoprene gloves
Administer oxygen, place on cardiac monitor, and measure pulse oximetry.
Establish IV access with 0.9% NS.

Ed Treatment/Procedures

Decontamination: Reduce secondary exposure
Blood agents:
- High flow 100% NRB oxygen
- Benzodiazepines for seizures
- Hydroxocobalamin (1st line)
- Cyanide antidote kit (2nd line), may be repeated.
Blister agents:
- Supportive care
- Standard burn management
- Atropine to relieve eye pain
- Monitor fluids, electrolytes, complete blood chemistry.
- Monitor CBC for nadir.
- Supportive care for sepsis, anemia, hemorrhage
- Granulocyte colony-stimulating factor (G-CSF) for neutropenia
Choking agents, lacrimators, riot control agents:
- Supportive care, bronchodilators
- Eye irrigation
- CXR and careful monitoring for respiratory complications
- Phosgenes require monitoring for delayed pulmonary edema for 24 hr
Nerve agents:
- Supportive care:
  - 100% oxygen
  - Frequent airway suctioning
- Atropine 2 mg IV q5min until reversal of bronchorrhea, bronchoconstriction, and hypoxemia:
  - Antagonizes muscarinic effects and some CNS but no effect on skeletal muscle weakness or respiratory failure
  - Pupillary response and heart rate are not useful measures of adequate atropinization.
  - Stop atropine after patient regains consciousness and spontaneous ventilation (may need for periodic relapses); give as much as it takes to reverse respiratory compromise.
- Pralidoxime chloride (2-PAM or Protopam):
  - Regenerates cholinesterase by reversing phosphorylation (unless aging has occurred)
  - Reduces abnormal skeletal muscle movements, improves skeletal muscle weakness, and reverses flaccid paralysis
  - May repeat 1st dose or start on continuous infusion
  - If improvement from 1st dose, repeat 60-90 min later.
- Diazepam: Administer for seizures.
Incapacitating agents (BZ):
- Supportive care
- Aggressive IV fluid hydration
- Benzodiazepines for agitation and increased muscular activity
- Consider physostigmine in consultation with a poison center.

Medication

Albuterol using nebulizer: 2.5 mg in 2.5 mL NS (peds: 0.1-0.15 mg/kg/dose)
Atropine: 2 mg IM or IV (5-6 mg in severely poisoned adults; peds: 0.02-0.08 mg/kg), then q5-10min titrate to clinical effect
Cyanide antidote kit:
- Inhale amyl nitrite ampule for 30 sec qmin until sodium nitrite given.
- Sodium nitrite: 10 mL of 3% solution or 300 mg IV over 3-5 min (peds: 0.15-0.33 mL/kg):
  - Monitor methemoglobin levels to keep <30%.
- Sodium thiosulfate: 50 mL IV of 25% solution or 12.5 g (peds: 1.65 mL/kg)
Diazepam: 5-10 mg IV over 3-5 min (peds: 0.2-0.4 mg/kg up to 10 mg over 2-3 min)
Hydroxocobalamin: 5 g IV
Pralidoxime chloride (2-PAM, Protopam): 1-2 g IV over 20-30 min or 600 mg IM (diluted with water or saline to concentration of 300 mg/mL) given with 1st 3 atropine doses (peds: 25-50 mg/kg/dose IV), repeat in 2 hr if muscle weakness has not been relieved, and in 4-6-hr intervals if necessary. Continuous infusion of 500 mg/h has been used for organophosphate poisoning

Follow-Up

Disposition

Admission Criteria

ICU admission for symptomatic patients with significant exposure
Hospital admission to monitor for developing complications for blister, choking, lacrimating agents, incapacitating agents

Discharge Criteria
Riot control exposures:

Observe in ED for 6 hr and discharge if symptoms resolve.

Pearls and Pitfalls

Must perform adequate decontamination

Additional Reading

Davis K, Aspera G. Exposure to liquid sulfur mustard. Ann Emerg Med. 2001;37:653-656.
Keyes DC. Chemical warfare agents. In: Dart RC, Caravati EM, McGuigan MA, et al., eds. Medical Toxicology. 3rd ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2004:1777-1794.

Codes

ICD9

987.5 Toxic effect of lacrimogenic gas
987.7 Toxic effect of hydrocyanic acid gas
987.9 Toxic effect of unspecified gas, fume, or vapor
987.6 Toxic effect of chlorine gas
987.8 Toxic effect of other specified gases, fumes, or vapors

ICD10

T57.3X4A Toxic effect of hydrogen cyanide, undetermined, init encntr
T59.3X4A Toxic effect of lacrimogenic gas, undetermined, initial encounter
T59.94XA Toxic effect of unsp gases, fumes and vapors, undet, init
T59.4X4A Toxic effect of chlorine gas, undetermined, initial encounter
T59.894A Toxic effect of gases, fumes and vapors, undetermined, init

SNOMED

243054000 Injury due to poison gas weapon (disorder)
243055004 Poisoning due to irritant gas
66207005 Toxic effect of cyanide (disorder)
243057007 Poisoning due to vesicant gas (disorder)
243056003 Poisoning due to crowd control gas (disorder)
243059005 Poisoning due to nerve gas (finding)

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