The chain of chemical survival - handout


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

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The chain of chemical survival - handout

  1. 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. 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. 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. 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. 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