Summary of preparatory reading for MUHC ED Disaster Preparedness Course for Residents

1. Adapted from Barelli et al, The comprehensive medical preparedness in chemical emergencies: ‘the chain of chemical survival’, European Journal of
Emergency Medicine 2008, 15:110–118
The Chain of Chemical Survival
HazMats (Hazardous Materials)
Substances that have the potential to harm
people or the environment either byitself or
through interaction with other factors. HazMats
can be gases, liquids, or solids and include
radioactive and chemical materials.
Globally Harmonized System of Classification and
Labelling of Chemicals (GHS) is a UN programme
that addresses classification of chemicals by types
of hazard and proposes harmonized hazard-
communication elements, including labels and
safety data sheets (See table 1).
Health hazard
Substances for which there is
statistically significant evidence based
on at least one study conducted in
accordance with established scientific
principles that acute or chronic health
effects may occur in exposed
individuals. (see Table 2)
Chemical weapons
Difficult to define as any chemical substance can be a weapon if used in an unauthorized or inappropriate way.
Simplified definition: Any weapon that
uses a manufactured chemical with high
killing power, meaning that it requires
small amounts of a chemical agent to kill
large numbers of people.
Chemical Weapons Convention: Defines
them as toxic substances with the
following characteristics:
(1) They have been developed, produced, stockpiled, or used as chemical weapons
(2) They pose a high risk to the objective and purpose of the convention by virtue of their high potential for use in
activities prohibited under the convention
(3) They have little or no use for purposes not prohibited by the convention
Examples in Table 4
Farooq Khan MDCM
PGY3 FRCP-EM
McGill University
November 14
th
2011

2. Adapted from Barelli et al, The comprehensive medical preparedness in chemical emergencies: ‘the chain of chemical survival’, European Journal of
Emergency Medicine 2008, 15:110–118
CDC categories
(1) Biotoxins
(2) Blister agents/vesicants
(3) Blood agents
(4) Caustics (acids)
(5) Choking/lung/pulmonary agents
(6) Incapacitating agents
(7) Long-acting anticoagulants
(8) Metals
(9) Nerve agents
(10)Organic solvents
(11)Riot control agents/tear gas
(12)Toxic alcohols
(13)Vomiting agents
4 basic categories of chemical weapons
1. Nerve agents: sarin, tabun, soman, and VX
2. Pulmonary and choking agents: phosgene and chlorine gases
3. Blood or asphyxiant agents: hydrogen cyanide and cyanogen chloride
4. Blister and vesicants: mustard, lewisite, phosgene, and oxime
Toxic syndromes relevant to medical management
Irritant gas, asphyxiant, cholinergic, corrosive, hydrocarbon, and halogenated hydrocarbon
Key points of medical care
Protection of healthcare personnel
Healthcare professionals require personal protective equipment (PPE) when performing essential response functions in
contaminated environments or with contaminated patients:
(1) First responders working in the hot zone;
(2) Emergency medical personnel in field decontamination;
(3) Emergency medical personnel at the hospital.

3. Adapted from Barelli et al, The comprehensive medical preparedness in chemical emergencies: ‘the chain of chemical survival’, European Journal of
Emergency Medicine 2008, 15:110–118
 First responders working in the hot zone (fire brigades) have to wear level-A suits.
 Emergency medical personnel in field decontamination require level-B protection, unless agent can be identified
and its concentration established as not being life-threatening, in which case most often level-C PPE is sufficient.
 A similar situation exists at hospitals that may receive not only field-decontaminated patients but also ‘walk-in’
patients, who may have bypassed field decontamination. Level-C protection (using a full-face mask with
powered or non-powered canister-filtration system) is considered adequate for hospital workers. Non-
identifiable substances and those with potential to re-aerosolize with clothing removal mandate organic
vapour/high-efficiency particulate air filter-cartridge mask
Problems and limitations
PPE takes time to wear and impairs dexterity and mobility: not fully trained emergency-care personnel may fail in
performing life-saving interventions. Impaired communication and vision result in poor speech intelligibility and
reduction in wearer’s visual field. Heat and psychological stress limit duration of use to no more than 20–30 min. The
higher the level of protection, the more difficult is the use.
Antidote Stockpiling
Antidotes, through enhanced elimination or direct counteraction of chemicals, may significantly reduce the medical
resources otherwise needed to treat a patient, shorten the period of therapy, and in some cases be a lifesaving
treatment.
Caveat: Misconception that there is an antidote for most poisons and underestimating role of routine management.
National programme of distribution of antidotes plays a fundamental role
 Limited by Demographic, geographical, and economic factors e.g. high cost, short shelf-life.
 Antidotes have been classified as those needed within the following lapses of time:
o Immediately (within 30 min)
 should be stocked at all hospitals, or in ambulances
o Within 2 h
 Can be stocked at a certain main hospitals
o Within 6 h
 Can be a central or regional depots (e.g. poison control center) and require transport system to
ensure availability or stock small amounts, sufficient to start treatment with locally, with further
supplies being obtained from a central source as required

4. Adapted from Barelli et al, The comprehensive medical preparedness in chemical emergencies: ‘the chain of chemical survival’, European Journal of
Emergency Medicine 2008, 15:110–118
Controversies: questionable safety and efficacy profiles as, no clinical trials exist. Information programmes should be
arranged by poison-information centres in order to familiarize clinical personnel with the proper use of antidotes
Cyanide
Most antidotes (e.g. nitrite, 4-dimethylaminophenol) can be toxic by interfering with tissue oxygenation themselves (e.g.
methemoglobinemia). Hydroxycobalamin has the most favourable side effect profile but requires very large doses.
Nerve agents
Atropine to counteract ACh effects, oximes reactivate inhibited AChE.
Obidoxime and pralidoxime (2-PAM) are effective against sarin, VX, and GF, but ineffective against soman and
cyclosarin. Therefore it is more appropriate to use HI-6 oximes that are effective against all nerve agents; unfortunately
these are not available in aqueous solutions and need to be stored as powder in a separate chamber of autoinjectors
Hydrazines
Colorless liquid with NH3-like odor found in rocket propellants and fuels, boiler-water treatments, chemical reactants,
medicines, and in cancer research.
Convulsive and lethal effects prevented by Pyridoxine hydrochloride
Patient Decontamination
Must be able to activate a plan to control the access of people to the indoor areas and to avoid secondary
contamination of health-care professionals and facilities
 Removal to an outside not-contaminated location
 Removal of clothing (with protection of privacy)
 Prioritize aerosolized or liquid exposures to eyes, skin or clothing
 To ensure rapid progression through the zone and save on hospital personnel, ambulatory patients should self-
decontaminate
 Multiple shower lines should be established allowing sequential copious warm-water rinse, a hypoallergenic
liquid soap wash, another warm-water rinse, and then a final rinse after walking past other in-use showers
 Showers permanently fixed to the ceiling structure of an open-air parking garage or to the side of a building to
allow immediate activation and minimal disruption of routine activities, but should provide shelter from
weather and adequate lighting
 Full passive and assisted decontamination should be available with adjustable water temperature
o Attention to washing and rinsing the patient’s back and the non-absorbent backboard
o Use sponges and disposable towels to avoid abrasion
Basic and Supportive Care
Quality supportive care has saved more poisoned patients than any antidote
Caveats to standard ABCDE approach in chemical exposures
Airway/Breathing
 In contaminated areas, ventilation should be performed using isolated BMV attached to either O2 or a filtered
compressor source to avoid pushing further toxin from ambient air into the lungs.

5. Adapted from Barelli et al, The comprehensive medical preparedness in chemical emergencies: ‘the chain of chemical survival’, European Journal of
Emergency Medicine 2008, 15:110–118
 Intubation provides the optimal isolation and protection
 Avoid if possible neuromuscular blocking agents or titrate small doses, e.g. succinylcholine hydrolyzed slowly in
nerve agent toxicity
 Rescue crics have unconfirmed safety in contaminated environments.
 LMA seals are inadequate with poor lung compliance
Circulation
 Placing an IV is awkward when wearing bulky PPE. Most antidotes can be administered quickly IM (e.g. atropine,
pralidoxime) provided there is sufficient perfusion of the tissues. Absorption can be erratic in shock states.
 Chemical agents can affect the circulation adversely through multiple mechanisms:
o Vagal stimulation,
o Fluids and electrolytes lost in exocrine-gland secretions or in chemical burns
o Direct depression of myocardial contractility
o Vasodilatation
Disability
 Convulsions can occur as direct toxicity (e.g. in nerve agents) or secondary to hypoxia
 Treat with benzodiazepines as 1st
line, consider barbiturate coma and EEG monitoring for status epilepticus, as
neuromuscular blockade masks motor activity but CNS seizures may still be present.
 Ensure adequate brain oxygenation.
Summary
The chain of chemical survival includes protection strategies, decontamination, antidote stockpiling and supportive care.
One weak link will cause the entire chain to be weak. There is no sense in developing and reinforcing only one link.
Avoid misconception of “one antidote – one poison”
Do not underestimate basic supportive care