Author:
Patrick M.Whiteley
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
- Lachrymators 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)
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:
- 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:
- Hematologic:
- Lachrymators 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 gland s
- 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
- Lachrymators (eye irritation, lacrimation, blepharospasm)
- Choking agents (dyspnea, bronchospasm)
Diagnostic 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
Prehospital
- Avoid contamination of environment and clinicians:
- Use level A or 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 (first line)
- Cyanide antidote kit (second line), may be repeated
- Blister agents:
- Supportive care
- Stand ard 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, lachrymators, 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 first dose or start on continuous infusion
- If improvement from first dose, repeat 60-90 min later
- Early use potentially beneficial. Unclear benefit in late presentation
- 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. Continuous infusions of 2 mg/min and higher has been used for organophosphate poisoning
- Cyanide antidote kit:
- Inhale amyl nitrite ampule for 30 s 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) (peds: 25-50 mg/kg/dose IV), given with first 3 atropine doses repeat in 2 hr if muscle weakness has not been relieved, and in 4-6-hr intervals if necessary. Continuous infusion of 2-PAM at 8 mg/kg/hr has been used for organophosphate poisoning