Irritant Gas Exposure, Emergency Medicine

Basics

Description

An irritant is any noncorrosive substance that on immediate, prolonged, or repeated contact with respiratory mucosa will induce a local inflammatory reaction.
Respiratory irritants are inhaled as gases, fumes, particles, or liquid aerosols.
Inhaled irritants:
- Pulmonary toxicity is determined primarily by their water solubility.
Inhalation accidents frequently involve a mixture of irritant gases as well as chemical asphyxiants:
- Carbon monoxide
- Hydrogen cyanide
- Hydrogen sulfide
- Oxides of nitrogen
Risk factors include exposure to potential irritants:
- Occupational
- Leisure
- Intentional
- Accidental
Pathophysiology:
- Cellular injury through interaction with respiratory mucosal water with subsequent formation of acids, alkalis, and free radicals

Etiology

Settings:
- Industrial: Chemical manufacturing, mining, plastics, and petroleum industries
- Home: Improper use or storage of cleaning chemicals
- Fires: Combustion yields toxic gases.
- Civil Disturbance: Riot control agents.
Immediate onset of upper airway inflammation with highly water-soluble irritant gases or with aerodynamic diameter >5 mm:
- Ammonia (fertilizers, refrigerants, dyes, plastics, synthetic fibers, cleaning agents):
  - Immediate symptoms range from mild edema and erythema to full-thickness burns and airway obstruction.
- Sulfur dioxide (fumigants used on produce, bleaching, tanning, brewing, wine making, combustion of coal, and smelting of sulfide-containing ores):
  - Combines with water, forming sulfuric acid.
- Hydrogen chloride (formed during combustion of chlorinated hydrocarbons such as polyvinyl chloride):
  - Combines with water, forming hydrochloric acid.
- Chloramine (generated when ammonia and bleach are mixed):
  - When exposed to moist surfaces, releases hypochlorous acid.
- Acrolein (production of plastics, pharmaceuticals, synthetic fibers; formed during combustion of petroleum products, cellulose, wood, paper):
  - May cause protein damage via free radical production and sulfhydryl binding.
- Formaldehyde (production of plywood, particle board, insulation; combustion product of gas stoves and heaters):
  - Combines with water to form sulfuric acid and formic acid.
- Hydrogen fluoride (combustion of fluorinated hydrocarbons):
  - Depletes calcium stores, resulting in cell death.
- Riot control agents (Capsaicin [OC], Chlorobenzylidenemalononitrile [CS], and Chloroacetophenone [CN]):
  - Lacrimation agents which cause temporary ocular discomfort.
Latent period of minutes to hours before onset of symptoms with irritant gases of intermediate water solubility or aerodynamic diameter of 1 " 5 mm:
- Chlorine (product of chlorinated chemicals; bleaching agent):
  - Upper and lower airway damage after reacting with water to form hydrochloric and hypochlorous acids
Delayed onset of symptoms up to 24 hr after inhalation with irritant gases of poor water solubility or aerodynamic diameter <1 mm (with little or no warning of exposure):
- Oxides of nitrogen produced:
  - In manufacture of dyes and fertilizers
  - By electric arc welding and gas blowing
  - By fermentation of nitrogen-rich silage (silo-fillers disease)
  - In combustion of nitrocellulose and polyamides
- Phosgene/carbonyl chloride (arc welding and pesticide production: Combustion of chlorinated hydrocarbons and solvents)
- Ozone (produced during arc welding)
- Cadmium oxide (oxyacetylene welding and electroplating)

Diagnosis

Signs and Symptoms

Dependent on water solubility
Highly water-soluble gases:
- Eye, nose, throat burning
- Shortness of breath
- Wheezing
- Cough
- Hoarseness
- Stridor
- Obstruction
Intermediate water solubility:
- Upper and lower tract involvement
- Mucosal irritation
- Bronchospasm
- Dyspnea
- Wheezing
- Cough
- Rales
- Possible delayed pulmonary edema
Other:
- Dermal irritation
- Headache
- Nausea
- Vomiting
- Confusion
- Seizures
- Syncope

History

Known exposures
Type of chemical/industry
Rapidity of symptom
Material safety data sheet from exposure site
Water solubility of agent

Physical Exam

HEENT:
- Conjunctival injection
- Lacrimation
- Chemosis
Respiratory
Stridor
- Voice changes
- Dyspnea
- Wheezing
- Cough
GI:
- Vomiting
Dermatologic:
- Skin erythema/irritation
- Erythematous rash
Neurologic:
- Confusion
- Seizure activity

Essential Workup

History of exposure to irritant gases in addition to noted symptoms confirm diagnosis.

Diagnosis Tests & Interpretation

ECG in the following patients:

Elderly
Cardiac history
Evidence of significant pulmonary symptoms

Lab

Arterial blood gas to assess:
- Oxygenation
- Ventilation status
- pH
- Pulse oximetry is unreliable.
Carbon monoxide level:
- If smoke inhalation with concomitant irritant gas inhalation (see "Carbon Monoxide Poisoning " )
Methemoglobin level:
- If oxides of nitrogen are suspected
Serum calcium level:
- If hydrogen fluoride is suspected
Lactate:
- Elevation may indicate cellular poisoning from carbon monoxide or cyanide.
Pregnancy test in all females of childbearing age
Rapid dextrose
Cardiac enzyme levels if acute coronary syndrome suspected

Imaging
CXR:

Frequently normal on initial presentation
May take up to 24 hr to reveal pulmonary edema or evidence of diffuse injury.

Diagnostic Procedures/Surgery

Spirometry:
- Assess evidence suggesting airway narrowing and bronchoconstriction.
Direct laryngoscopy:
- Assess evidence of upper airway edema.
Corneal fluorescein:
- Assess evidence of corneal burns/injury.

Differential Diagnosis

Asthma exacerbation
Allergic stimuli (pollen)
Physical stimuli (cold air)
Bronchitis
Pneumonia
Occupational asthma
Hypersensitivity pneumonitis
Congestive heart failure

Treatment

Pre-Hospital

Rescuers goal is to prevent self-contamination with use of protective clothing or equipment (self-contained breathing apparatus).

Initial Stabilization/Therapy

ABCs:
- 100% oxygen through a tight-fitting, nonrebreathing face mask
- Early intubation may be necessary to protect airway from edema.
- Mechanical ventilation
- Continuous positive airway pressure or positive end-expiratory pressure may enhance oxygenation.
Decontaminate by removing clothes and irrigating skin and ocular tissues.

Ed Treatment/Procedures

Inhaled nebulized ²2-adrenergic agonists (albuterol) for bronchoconstriction
Inhaled/IV/PO corticosteroids: Beclomethasone, methylprednisolone, prednisone:
- Controversial
- No controlled trials that document benefit of acute corticosteroids after irritant gas inhalation.
Nebulized sodium bicarbonate (3.75% solution) after chlorine gas exposure:
- Reported to improve oxygenation in several case reports/series.
Nebulized calcium gluconate after acute hydrogen fluoride inhalation:
- Reported, but with no proven benefit
Hydroxocobalamin or cyanide antidote kit if hydrogen cyanide is suspected (see "Cyanide Poisoning " )
Oxygen or hyperbaric oxygen therapy if carbon monoxide poisoning documented

Medication

Albuterol: 0.5 mL (peds: 0.03 mL or 0.15 mg/kg/dose) of 0.5% solution diluted in NS to 3 mL aerosolized
Beclomethasone MDI: 1 " 2 sprays (40 " 80 Ό/spray) BID
Calcium gluconate: Nebulized (2.5 " 3% solution) prepared by adding 0.15 g of calcium gluconate to 6 mL of NS
Methylprednisolone: 80 " 125 mg (peds: 1 " 2 mg/kg) IV
Prednisone: 40 " 80 mg (peds: 1 " 2 mg/kg) PO
Sodium bicarbonate: Nebulized (3 mL of 8.4% sodium bicarbonate mixed with 2 mL of NS to prepare 5 mL of 5% solution)

Follow-Up

Disposition

Admission Criteria

ICU admission:
- Intubated patients
- Significant respiratory insufficiency or potential upper airway obstruction
Persistently symptomatic with bronchospasm or oxygen requirement
Exposure to irritant gases that affect peripheral airways:
- Delayed pulmonary edema and respiratory failure may occur.
Conservative treatment for children, pregnant women, elderly patients, or those with pre-existing chronic obstructive pulmonary or coronary disease

Discharge Criteria

Mild exposures that respond well to supportive care and have no oxygen requirement or bronchospasm after 4 " 6 hr of observation
Follow-up chest radiograph during observation and prior to discharge, especially if any symptoms are present or clinically worsening

Issues for Referral
Intensive care for patients with early evidence of acute lung injury

Follow-Up Recommendations

Occupational medicine referral for work-related exposures.
Pulmonary follow-up for repeated symptomatic exposures.

Pearls and Pitfalls

Beware of delayed onset of low-solubility agents. These exposures may require 23-hr observation for delayed respiratory symptoms.
Avoid exposure of agent to first responders, with appropriate decontamination.

Additional Reading

Bosse GM. Nebulized sodium bicarbonate in the treatment of chlorine gas inhalation. J Toxicol Clin Toxicol. 1994;32:233 " 241.
Rorison DG, McPherson SJ. Acute toxic inhalations. Emerg Med Clin North Am. 1992;10:409 " 435.
Taylor AJ. Respiratory irritants encountered at work. Thorax. 1996;51:541 " 545.
Vinsel PJ. Treatment of acute chlorine gas inhalation with nebulized sodium bicarbonate. J Emerg Med. 1990;8:327 " 329.
Weiner AL, Bayer MJ. Inhalation: Gases with immediate toxicity. In: Ford MD, Delaney KA, Ling LJ, et al., eds. Clinical Toxicology. Philadelphia, PA: WB Saunders; 2001.
Weiss SM, Lakshminarayan S. Acute inhalation injury. Clin Chest Med. 1994;15:103 " 116.

Codes

ICD9

986 Toxic effect of carbon monoxide
987.7 Toxic effect of hydrocyanic acid gas
987.9 Toxic effect of unspecified gas, fume, or vapor
987.8 Toxic effect of other specified gases, fumes, or vapors
987.2 Toxic effect of nitrogen oxides
987.3 Toxic effect of sulfur dioxide
987.6 Toxic effect of chlorine gas

ICD10

T57.3X1A Toxic effect of hydrogen cyanide, accidental (unintentional), initial encounter
T58.91XA Toxic effect of carb monx from unsp source, acc, init
T59.91XA Toxic effect of unsp gases, fumes and vapors, acc, init
T59.6X1A Toxic effect of hydrogen sulfide, accidental (unintentional), initial encounter
T59.0X1A Toxic effect of nitrogen oxides, accidental (unintentional), initial encounter
T59.1X1A Toxic effect of sulfur dioxide, accidental (unintentional), initial encounter
T59.4X1A Toxic effect of chlorine gas, accidental (unintentional), initial encounter
T59.891A Toxic effect of other specified gases, fumes and vapors, accidental (unintentional), initial encounter

SNOMED

419181004 Exposure to gaseous substance (event)
95875007 Exposure to carbon monoxide (event)
38704001 Toxic effect of hydrocyanic acid gas (disorder)
212858000 toxic effect of hydrogen sulfide (disorder)
24310001 Toxic effect of sulfur dioxide (disorder)
8904001 Toxic effect of nitrous fumes (disorder)
90765000 Toxic effect of chlorine gas (disorder)

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