INCAPACITATING AGENTS

Background

Incapacitating agents produce temporary physical and/or mental effects that result in the inability of the affected individual to continue in their current duties or activity. Often they are described as non-lethal agents, but if administered in high enough doses, incapacitating agents can results in death or serious morbidity. There are three general categories of incapacitating agents:61

1. Anticholinergics

BZ (3-quinuclidinyl benzilate) is the prototypical anticholinergic agent but other anticholinergic agents may be developed for warfare. The British reportedly have a similar agent known as Agent 15. BZ is a centrally acting anticholinergic agent that was originally developed as a gastrointestinal antispasmodic but due to severe central nervous system effects was abandoned as a pharmaceutical. As an incapacitating agent, it has a very high safety profile due to the relatively lower peripheral antimuscarinic effects when compared to atropine. An effective incapacitating dose is 0.5 mg, and BZ is typically dispersed as an aerosol or in smoke-producing munitions.

2. Sedating agents

Opioids and volatile anesthetics are both potential sedative or calming agents. Fentanyl is a synthetic opioid with 100 times the potency of morphine. Newer derivatives of fentanyl are continuously in development. One such example is carfentanil with a potency 100 times fentanyl. While these agents are highly effective in individuals, aerosolizing them to use as an incapacitating agent can be problematic. It is likely that absorption in a crowd would be variable.

3. Riot control agents

Riot control agents, also known as harassing agents, cause irritation and discomfort often in the form lacrimation, mucous membrane irritation, violent coughing, or vomiting. Typical agents include chloroacetophenone (CN) commonly known as Mace, chlorobenzylidene malononitrile (CS), oleoresin capsicum (OC) called pepper spray, and diphenylaminochloroarsine (DM) or Adamsite. CN is more harmful than the other agents with a lower LCt50 and DM tends to cause vomiting.

Signs and Symptoms of Incapacitating Agents

- Anticholinergics

BZ is intended to target CNS effects, therefore anticholinergic delirium will be the predominant symptom with fewer peripheral effects. Often the patient cannot give a lucid history due to delirium. The delirium may be labile and can range from mild impairment to coma. Hallucinations, severe agitation, and even seizures may occur. The classic peripheral effects often described a “dry as a bone, hot as a hare, red as a beet, and blind as a bat” may be variable or delayed.

- Sedating agents

Sedating agents which are opioid derivatives can be expected to present with the classic opioid toxidrome of miosis, CNS depression, and respiratory depression. Bradycardia, hypotension, and hypothermia may occur as secondary sequelae as a result of dose-related progression to opioid coma.

- Riot control agents

Riot control agents can be expected to affect the skin, respiratory system and eyes. Ophthalmologic symptoms include pain, tearing, and blepharospasm. The respiratory tract can be variably affected and symptoms may range from mild mucous membrane irritation to severe dyspnea, coughing and chest tightness. Bronchospasm is common and may be severe in those with underlying reactive airway disease. Copious rhinorrhea and salivation may occur and clinical scrutiny is necessary to exclude the possibility of nerve agent exposure. Dermatologic effects typically involve skin pain and burning, but blistering may occur at higher doses.

General Management

Safe removal from exposure is the priority. Respiratory protection for providers in a potential exposure area is critical. Once the casualty is removed from the exposure area, decontamination can be continued with removal of all clothing and personal effects. Simple soap and copious water are adequate for through decontamination. Recognize that improvement in symptoms caused by riot control agents may be transient with decontamination.

Medical management of all incapacitating agents is predominantly supportive with attention to symptoms and tailoring treatment to the patient presentation.

Anticholinergic agents

Patients with anticholinergic toxicity can present with dry mouth and tachycardia leading the provider to believe dehydration is present when the patient is euvolemic. However, psychomotor agitation and hyperthermia are common so careful monitoring of core temperature, volume status and urine output is important. Cooling should be undertaken promptly when hyperthermia is present.

Pharmacologic managements include control of delirium and agitation. Agitation can be safely controlled with a benzodiazepine titrated to effect. Often controlling the agitation will also improve tachycardia and hyperthermia. Physostigmine is also an option to manage the delirium. This is a tertiary amine which crosses the blood-brain barrier. Before using physostigmine, it is critical to exclude the presence of other sodium channel blocking agents such as tricyclic antidepressants. An EKG should be done to ensure a normal QRS interval <100msec prior to physostigmine use, which limits its utility when EKG is not immediately available. Additionally, atropine should be ready in case there is a cholinergic response that affects the airway. In most cases, benzodiazepines are considered the primary treatment option since they can be administered safely to almost any patient.

Sedating agents

Support of the respiratory system is the primary focus for treatment of opioid toxicity associated with sedating agents. Naloxone is the antidote of choice and should be titrated to reverse respiratory suppression. Nasal naloxone can be rapidly administered without IV access. Naloxone should be titrated to effect. A starting dose of 2-4 mg is appropriate but much higher doses may be required to reverse the effects of synthetic opioids. The half-life of naloxone may be shorter than the half-life of the agent and repeat dosing or a naloxone drip may be necessary.

Riot control agents

Most riot control agents are short acting and supportive care is usually adequate until symptoms subside.

Incapacitating Agent Diagnostics

Laboratory values are of little diagnostic utility. Opioids may be detected on routine toxin screen.

Incapacitating Agent Treatment

Advanced interventions and the supporting evidence are described in the table below.