Chemical weapons
Background
- Can be released via unintended means such as a spill from a damaged railroad tank car or industrial explosion as well as by intentional means as chemical weapons.
Pediatric considerations
- Higher metabolic rate and faster basal respiratory rate, causing more rapid and larger exposures
- Skin is thinner and more permeable
- Agents heavier than air have increased concentrations closer to the ground exposing children > adults
Types
Chemical weapons
- Blister chemical agents (Vesicants)
- Lewisite (L)
- Sulfur mustard (H)
- Phosgene oxime (CX)
- Pulmonary chemical agents (Choking agents)
- Incendiary agents
- Cyanide chemical weapon agents (Blood agents)
- Prussic acid (AKA hydrogen cyanide, hydrocyanic acid, or formonitrile)
- Nerve Agents (organophosphates)
- Acetylcholinesterase inhibitors
- Household and commercial pesticides (diazinon and parathion)
- G-series (sarin, tabun, soman)
- V-series (VX)
- Lacrimating or riot-control agents
- Pepper spray
- Chloroacetophenone
- CS
Cyanide Agents (CN)
- AKA Hydrocyanic acid, Formonitrile, Prussic acid
- Mimics carbon monoxide poisoning
- Smell of bitter almonds but not all people can smell cyanide
- Absorbed through skin, inhaled or ingested
- Can affect individuals near fire with synthetic materials or plastics
- Can penetrate rubber and barrier fabrics
Pathophysiology
- Cyanide inhibits cytochrome oxidase on mitochondria
- Cells unable to use oxygen in bloodstream
- Cellular asphyxiation
Symptoms
- Symptoms can be delayed up to 60 minutes
- Symptoms dependent on concentration, form of cyanide, and route of exposure
- CNS and cardiovascular system most susceptible
- Initially hypertension and tachycardia progressing to bradycardia, hypotension, and arrhythmias late
- Anxiety, dizziness, headache, apnea, seizures, and coma
Management
- 100% oxygen and antidote therapy
- Sodium nitrite (IV) or amyl nitrite (inhaled) to displace cyanide from cytochrome oxidase
- Sodium thiosulfate: For conversion of cyanide to excretable thiosulfate
- Repeat sodium nitrite and sodium thiosulfate in 30min at half initial dose if needed
- Hydroxocobalamin (Vit B12a): makes CN water soluble and non-toxic
- Cyanide Antidote Kit: Amyl nitrite pearls, sodium nitrite (IV), sodium thiosulfate (IV)
- Cyanokit: Less toxic than cyanide antidote kit and shown effective in cardiac arrest
Nerve Agents
- Acetylcholinesterase inhibitors
- Includes household and commercial pesticides (diazinon and parathion)
- G-series (sarin, tabun, soman) and V-series (VX)
- G-series are volatile non-persistent agents that evaporate quickly
- V-series high viscosity with oily consistency
- Rapidly absorbed through skin, symptoms generally develop within 1 hour
- Vapors are heavier than air and tend to sink into low places
- Sarin used in Tokyo subway attack in 1995; 5,000 sought medical attention with 12 deaths.
Pathophysiology
- Inhibits acetylcholinesterase → excess acetylcholine at both nicotinic and muscarinic receptors
Symptoms
- DUMBELLS
- D-Diarrhea, U-Urination, M-Miosis, B-Bronchorrhea/Bradycardia, E-Emesis, L-Lacrimation, S-Salivation/Seizures
- Cholinergic toxidrome Toxidromes
Management
- Nerve agents prolong succinylcholine's paralytic effect
- Atropine for bronchorrhea and bronchoconstriction
- Start at 2-6mg, double the dose q5-30min until control of secretions (no max dose)
- Pralidoxime to restore function of acetylcholinesterase (given over approximately 30 minutes; rapid infusion can cause hypertension)
- Give as soon as possible - must be given before "aging" occurs to be effective
- Benzodiazepines for seizures (standard AEDs may be ineffective)
- Mark 1 Nerve Agent antidote Kit (NAAK): 2 autoinjectors:
- 2mg atropine
- 600mg pralidoxime
- DuoDote Autoinjector: 2.1mg atropine, 600mg pralidoxime in one autoinjector
- Prophylaxis in the military, high risk setting with pyridostigmine
- Reversibly bind acetylcholinesterase before exposure to nerve agents
- Pyridostigmine 30 mg PO q8[1]
Differential Diagnosis
Mass casualty incident
- Radiation exposure (disaster)
- Dirty bomb
- Bioterrorism
- Chemical weapons
- Mass shooting
- Natural Disaster (e.g. Hurricane, Earthquake, Tornado, Tsunami, etc)
- Unintentional large-scale incident (e.g. building collapse, train derailment, etc)
- Major pandemic
- Explosions
Toxic gas exposure
- Carbon monoxide toxicity
- Chemical weapons
- Cyanide toxicity
- Hydrocarbon toxicity
- Hydrogen sulfide toxicity
- Inhalant abuse
- Methane toxicity
- Smoke inhalation injury
- Ethylene dibromide toxicity
Management
- Depends on specific agent used
- Regardless of agent, Decontamination and ABCs are of primary importance
- Use appropriate personal protective equipment (PPE)
- Decontamination (should take place pre-hospital or otherwise prior to entering the ED)
- Remove all patient clothing
- Brush off dry agent (e.g. powders), copiously irrigate skin of any liquid contaminant
See Also
References
- ↑ Dunn MA, Sidell FR. Progress in medical defense against nerve agents. JAMA. 1989;262:649–652.