Chemical incidents

Learning objectives.

By reading this article, you should be able to:

• •Explain the key principles in the prehospital management of a chemical incident.
• •Discuss the safety considerations for the management of casualties exposed to hazardous materials.
• •Describe the more significant toxidromes and outline the initial management and their implications for the anaesthetist.

Key points.

• •Chemical incidents present a continuing risk to patients and responders, requiring personal protective equipment and control measures.
• •Incidents may not be initially obvious, so follow the Safety Triggers for Emergency Personnel 1-2-3 tool.
• •Safety considerations, incident reporting, scene and casualty assessment, life-saving interventions and decontamination are all relevant.
• •The National Poisons Information Service should be contacted early.
• •Major chemical incidents require specific triage tools and decontamination zones.

Chemical incidents are defined by the WHO as the uncontrolled release of a toxic substance, potentially resulting in harm to public health and the environment.¹ The cause of a chemical incident can be an unintentional release of hazardous material (HAZMAT) as a result of an industrial or transportation accident, or a deliberate release attributable to terrorism or act of war, often described as a chemical, biological, radiological or nuclear (CBRN) incident.² In the UK, there has been an increase in the use of caustic substances (acids or alkalis) as a targeted assault.

Tragically, the use of chemicals in deliberate acts of terrorism and warfare is not new with incidents in World War 1 demonstrating the devastating effects of chlorine, phosgene and sulphur mustard gas.³ In more recent history, chemical weapons have been used in major cities in civilian attacks, such as the use of sarin in Syria from 2013 and the Salisbury nerve agent incident in the UK in 2018. The increased use of chemical agents in acts of terrorism has led to guidance from Public Health England supporting the clinical management and health protection in CBRN incidents, and international guidelines from the North Atlantic Treaty Organization.⁴

Domestically, the use of chemicals, particularly caustic substances, in violent assaults has increased dramatically in the UK, with 501 attacks reported in 2018.⁵ The majority of these incidents have occurred in London, and unlike in other countries, these incidents appear to be gang-related with victims and perpetrators mostly male. In these attacks, the target is often the victim's face to cause maximal disfigurement by scarring and deformity, bringing long-term physical and psychological damage.⁶

Prehospital management

Principles

The principles of CBRN casualty care include:

• (i)Recognition of a CBRN casualty or incident
• (ii)Safety considerations
• (iii)First aid or buddy/citizen aid
• (iv)Triage to identify any severe (P1) cases
• (v)Life-saving interventions
• (vi)Decontamination
• (vii)Advanced medical care (including supportive and definitive care)
• (viii)Rehabilitation

Recognition of chemical incidents

Chemical incidents may occur without any warning and produce an environment unfamiliar to emergency services. This environment may include the presence of multiple dead or distressed people and animals; individuals showing unexplained symptoms (such as skin, eye and airway irritation; sweating; seizures; and vomiting); or even the more obvious presence of a HAZMAT represented by a smell, taste or appearance of an unexplained vapour, mist cloud or oily droplets on surfaces.⁷ The use of conventional weapons may also mask, by distraction, the presence of chemical substances, placing the emergency response at further risk and delaying treatment to the victims. It may therefore not be immediately obvious that a CBRN incident has occurred with identification only occurring through toxidrome recognition during or after the initial treatment of casualties. The ‘Safety Triggers for Emergency Personnel (STEP) 1-2-3 Plus’ (Table 1) is a useful tool for emergency personnel approaching any incident when the cause is unknown.⁸

Table 1.

Safety Triggers for Emergency Personnel 1-2-3 Plus. CBRN, chemical, biological, radiological or nuclear

Step	Number of casualties	What to do
1	One	Approach this using normal procedure. CBRN contamination is unlikely.
2	Two	Approach with caution; consider all options. CBRN contamination is possible. Report on arrival; update control. If possible or suspected, follow advice for Step 3.
3+	Three or more	Use caution and step ‘plus': Follow the CBRN first responder flow chart. The main principles include evacuation, communication, disrobing and decontamination.

Safety considerations

As with all prehospital scenes, safety is prioritised in the order of personal safety, the team's safety and the patient's safety. If, after applying the STEP 1-2-3 Plus tool, three or more casualties are suspected to be involved in a chemical incident, the first response is to withdraw from the scene and encourage those people that are able to evacuate upwind and preferably uphill.⁹ If the incident has occurred indoors, then those uninjured should remain in shelter with the doors and windows shut. The initial operational response, as outlined by the Home Office and the Joint Emergency Services Interoperability Principles for joint working, is that a situation report should be delivered as soon as possible to establish shared situational awareness amongst all the emergency services involved.¹⁰ The information contained in this report should be based on the METHANE or ETHANE system of reporting depending on whether it reaches the threshold to be declared a major incident:

• M: major incident declared/standby

• E: exact location

• T: type of incident

• H: hazards

• A: access and egress

• N: number of casualties

• E: emergency services required

Key safety considerations include:

• (i)Appropriate personal protective equipment (PPE) should be used by trained personnel.
• (ii)Establish hazard zones (hot and warm) and cordons, including a clean/dirty line (CDL).
• (iii)Assess the risk of contamination with other emergency services.
• (iv)Communicate with other on-scene responders and hospitals.

Communication with casualties that are able to mobilise is vital, and after initial evacuation to a place of relative safety, the process of disrobing and decontamination should be commenced as soon as possible. Disrobing within 15 min of exposure is highly effective at reducing the effects of CBRN materials, and disrobing packs with instructions are available on many fire and rescue service vehicles.¹¹ Casualties and rescuers should be advised not to eat, drink or smoke, and to avoid touching their face because of the risk of ingesting or transferring HAZMATs.

These principles of situation reporting, evacuation, disrobing and decontamination make up the priorities of the initial operational response, and the faster it is, the greater is the chance of saving lives. This is summarised by: remove from the hazard, remove clothing and remove any contamination.

Hazard zones

The chemical incident may be divided into a number of zones based on the level of chemical hazard. Unlike conventional scenes, which may be concentric, chemical hazard zones may have a geometry skewed because of the wind and other geographical features. The ‘hot zone’ is the area where there is a continuing hazard in the environment requiring the use of PPE and other control measures. An ‘exclusion zone’ is a type of hot zone, but which has a hazard that cannot be mitigated by PPE (e.g. explosive hazard or high dose-rate radiation hazard); distance is therefore a better control measure. The ‘warm zone’ is the area where there is a residual hazard on equipment, personnel or casualties transiting from the hot zone. This may also become a decontamination zone to remove or contain the hazard. On crossing the CDL, the clean or ‘cold’ zone is entered. In some circumstances, such as wound contamination, there may still be a residual risk.

Personal protective equipment

Personal protective equipment will protect you, your colleagues and patients from hazardous chemicals, but only if selected, worn (donned) and removed (doffed) correctly. On scene at a chemical incident, the level of appropriate PPE depends on the area that you are working in. Usually, only specialist medical teams, such as the hazardous area response team or medical emergency response incident team, will have had the appropriate training for the PPE required in the hot and warm zones. NHS chemical PPE includes a chemical respirator (integral to PPE), chemical-resistant gloves, coverall and integral hood and boots.

Rescuers in the cold zone, outside the inner cordon, do not require this level of specialist PPE, and should use gloves, gown, mask and eye shielding. Donning and doffing of PPE should be considered as critical procedures with due care and attention taken at each stage.

Decontamination

Decontamination is ideally performed on scene, after any chemical incident or assault, with the aim to reduce harm to the patient, to others and the wider environment. In large incidents, with multiple casualties, it should be expected that contaminated casualties might present themselves to the emergency department, necessitating the availability of NHS secondary care decontamination facilities.

If there is a life-threatening condition (catastrophic haemorrhage, airway obstruction, respiratory distress, reduced conscious level or seizures) present, then life-saving interventions must be provided with concurrent decontamination. Removal of clothing will be needed for access to the patient to give life-saving treatment.

The Optimisation, through Research, of Chemical Incident Decontamination Systems (ORCHIDS) project has produced an evidence base for current decontamination methods that include disrobing, improvised dry contamination and improvised wet decontamination.¹²

Disrobing or undressing is a critical part of the decontamination process, as it is effective at removing up to 90% of the contaminant load. Both are deemed procedures and should be done in a systematic way as per the Home Office guidance. Removed clothing should be stored in sealed bags for evidence collection and possible repatriation. Where possible, the dignity of casualties should be maintained.

Improvised decontamination is the use of immediately available resources to decontaminate a casualty. In the UK, dry decontamination is the method of choice unless a caustic or irritant chemical is suspected when wet decontamination is preferred.

Improvised dry decontamination involves the use of any dry absorbant material, such as towels, tissue paper, etc., to blot and rub the infected skin. Care should be taken to avoid transfer from one area to another, and both rubbing and blotting should not be too aggressive. Any waste material from this procedure should be bagged and left for disposal later. Where possible, casualties should be encouraged to perform this procedure themselves to avoid harm to others.

Improvised wet decontamination requires water from any available source (preferably warm to avoid hypothermia), a bucket to contain it, a second bucket containing a water and detergent mix and a sponge or brush. The ‘rinse–wipe–rinse’ technique is used, and it should take approximately 90 s to complete one cycle: rinse the affected areas with clean water from the highest point downwards, wipe the affected areas with a sponge or brush soaked in the detergent mix and then rinse this off again with clean water. The skin should be dried after each cycle with a towel, and the cycle should only be repeated if skin contamination remains obvious. When there are large numbers of casualties, ambulatory patients will be decontaminated in a shower tent, whilst the non-ambulatory patients will be managed by a decontamination team in a specialised decontamination tent. The use of this specialised equipment from fire and rescue services is often referred to as interim decontamination.

Clinical response

After decontamination, prehospital treatment should follow a standardised approach with an adapted primary survey (CBRN emergency medical treatment):

• (i)Catastrophic haemorrhage (<C>) management, including tourniquet use
• (ii)Airway management (A), including chemical-induced secretions
• (iii)Antidote therapy (a) usually by auto-injector, intraosseous or i.v. routes, if available
• (iv)Breathing management (B), including oxygen, if practicable
• (v)Circulation management (C), including fluids, if required
• (vi)Decontamination (Decon) and disability (D)
• (vii)Evacuation (Evac) to the next zone or medical facility

The level of care will depend on the zone and medical priority. Management in the hot zone is limited to <C>AB and evacuation. This is summarised in Figure 1 with casualty or clinical decontamination areas.

Fig 1.

Summary of chemical, biological, radiological or nuclear first aid and emergency medical treatment. <Cat Haem>, catastrophic haemorrhage; CCS, casualty clearing station; (Fwd) CCP, (forward) casualty collection point; PoE, point of exposure.

Early consideration should be given to identify the chemical used, with the National Poisons Information Service (NPIS) readily available to assist in toxidrome recognition. The rapid onset of symptoms seen with agents such as cyanide and nerve agents, and the availability of effective antidotes make the early recognition of these particular toxidromes imperative to increasing patients' survival. A CBRN toxidrome aide memoire based on conscious level, respiration, eyes, secretion and skin and other features is shown in Table 2.

Table 2.

Conscious level, respiration, eyes, secretion and skin (CRESS) assessment for medical responders.

Extended C R E S S	Nerve agent	Vesicants (blistering agents)	Pulmonary agents	Cyanide/Hydrogen sulphide	Met-Hb	Opioids	Atropine	Sepsis	Botulinum toxin	Heat stroke
	THIS LIST IS NOT EXHAUSTIVE AND NOT ALL FEATURES MAY BE PRESENT
Consciousness	Convulsions	Normal	Normal/Agitated	Unconscious/Convulsions	Agitated	Reduced → Unconscious	Agitated/Confused	Normal, reduced or altered	Normal	Altered
Respiration	Increased or reduced → stopped	Normal/Increased	Increased	Increased or stopped	Normal/Increased	Reduced → stopped	Increased	Increased	Reduced	Increased
Eyes	Pinpoint pupils∗	Normal/Inflamed	Normal/Inflamed	Normal/ Dilated pupils	Normal	Pinpoint pupils	Dilated pupils/Blurred vision	Normal	Dilated pupils/Blurred vision	Normal/ Dilated pupils
Secretions	Increased∗	Normal/Increased	Increased/Pink tinged sputum	Normal	Normal	Normal	Dry mouth/Thirsty	Normal/Sputum	Dry mouth/Thirsty	Normal
Skin	Sweaty	Red/Blistered	Cyanosed	Pink → cyanosed	Cyanosed	Normal/Cyanosed	Flushed/Dry	Warm → pale Non-blanching rash	Flushed/Dry	Varied
Other features	Altered vision Headache Vomiting Incontinence Slow pulse	Rapid: Caustic agent, Lewisite Delayed (6–24h): Sulphur mustard		Sudden onset Arterialised venous blood Raised lactate	Chocolate-coloured blood No improved cyanosis or O2 saturations with oxygen	Chest wall rigidity/myoclonus associated with fentanyls	Tachycardia	Fast pulse Fever (>38.3°C) Biosyndrome† Hypotension (< 100 mmHg)/no radial pulse	Descending paralysis including ptosis and dysphagia	High temperature (>38°C)
Initial treatment	Atropine Oxime Benzodiazepine	Lewisite: Chelating agents HF: Calcium	Supportive	See local guidance	Methylene blue	Naloxone	Supportive (physostigmine)	Sepsis Six	Botulinum antitoxin	Urgent cooling Supportive

∗ Pinpoint pupils (or increased secretions) may be delayed if skin absorption or eye protection worn. ^†‘Biosyndromes’ include: respiratory, cutaneous (skin), lymphadenopathy, haemorrhagic, gastrointestinal and neurological (central and peripheral). 2016 Criteria for Sepsis: 2 of 3 – altered conscious level; ventilatory frequency ≥ 22; or systolic blood pressure < 100 mmHg with or without non-blanching rash (additional NATO criterion) [see AmedP-7.1 Part 4]. Consider SEPTIC SHOCK if systolic pressure < 90 mmHg or no radial pulse.

Incident management and public health advice is provided by Public Health England (and devolved administrations' equivalent), through the Emergency Coordination of Scientific Advice. Further recognition may be supported by on-scene assessment usually by the fire and rescue service. This includes special monitoring equipment and visual hazard warnings, such as the UK transport hazard information system sign (Fig. 2) that displays a Hazchem/emergency action code, United Nations (UN) number and a UN warning label alongside a specialist advice telephone number and the company logo.

Fig 2.

UK transport hazard information system (UKTHIS) sign (reproduced with permission, under the terms of the Open Government Licence v3.0).

Drivers of vehicles that contain HAZMATs should also keep an A4 Transport Emergency Card at the rear of their seats. The information contained on these cards includes the British Standards chemical name of the substance, a description of its appearance and physical properties, the appropriate PPE required for handling, advice on immediate management of spillage or fire and first-aid management of contaminated casualties.

European regulation from 2015 on classification, labelling and packaging of chemical substances governs the presentation of hazard labels (Fig. 3). Safety data sheets should also be available with any hazardous substance or mixture.

Fig 3.

Hazard labels (reproduced with permission, under the terms of the Open Government Licence v3.0).

Recognition and management of specific toxidromes

Chemical incidents can be broadly classified by the family of causative agents: caustic agents, nerve agents, blistering agents, pulmonary agents, haemoglobin poisons, chemical asphyxiants, toxins, incapacitating agents and riot control agents. A detailed summary of these groups, including examples, mechanisms and practical implications for the anaesthetist is available in Supplementary Table S1.^13,14

Major chemical incidents and mass casualties

A major incident is defined as any incident, where the location, number, severity or type of live casualties requires extraordinary resources. Where a chemical incident is suspected, it is likely that those resources will be the same with respect to the fire and rescue service and the ambulance service. A CBRN, or CBRN(e) if in the presence of an explosion, event is, by definition, an act of terrorism, and as a result of this, the response is police led, with them retaining overall responsibility for the coordination of the multi-agency response.

The key principles for dealing with a major incident follow the order command, safety, cordon, control, communication, assessment, triage, treatment and transport, amended from the conventional incident response as outlined by the National Ambulance Resilience Unit and described by Lowes and Cosgrove.^15,16 Key differences during a CBRN or HAZMAT incident are with regard to safety, in particular PPE and designated decontamination zones, and triage (see Fig. 4).

Fig 4.

CBRN triage sieve. GCS, Glasgow Coma Scale; VF, ventilatory frequency.

Summary

The incidence of chemicals used in violent assaults within the UK is increasing, and whilst there is a threat of terrorism or warfare in the world, chemical weapons may be present. The use of chemicals in manufacturing processes means that there is always potential for a chemical incident, with accidents at work or during transfer of HAZMATs. Clinicians involved in any of these incidents, both outside and within hospitals, need to remain vigilant to the possibility of their presence and the dangers they present to the responder and the casualty. Management of the patient is specific to the chemical used and often requires extensive critical care resources, provided under the guidance of NPIS and Public Health England.

Declaration of interests

The authors declare that they have no conflicts of interest.

Biographies

James SenMRCP FRCA FFICM DIMC RCSEd is a specialty registrar in anaesthesia and intensive care medicine. He is also a member of the West Yorkshire Medical Response Team.

Raj SandhuMRCP FRCA FFICM is a consultant in burns anaesthesia and intensive care medicine at Pinderfields Burn Centre where he has managed victims of chemical incidents. He is the president of the Yorkshire Society of Anaesthetists.

Surgeon Commander Steven BlandMSc (MedTox) FRCEM is a consultant in emergency medicine; the defence consultant advisor in chemical, biological, radiological and nuclear (CBRN) medicine and chair of the North Atlantic Treaty Organization (NATO) CBRN medical working group. He has written a number of UK and NATO CBRN clinical guidelines, and developed military and NHS CBRN medical courses.

Matrix codes: 1A02, 2A02, 3A10

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Supplementary material

The following is the Supplementary data to this article: