Chemical Agents: Nerve Agents and Their Antidotes Practice Questions

25 multiple-choice questions on Chemical agents: nerve agents and their antidotes for paramedic and EMT students, from Chapter 51 (Terrorism Response). Read each question, pick your answer, then tap Show answer to check it and read the explanation.

25 practice questions

1. Military nerve agents such as sarin are chemically related to:

   1. A. Cyanide-based fumigants
   2. B. Chlorine-based bleach compounds
   3. C. Organophosphate insecticides
   4. D. Opioid anesthetic gases
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   Answer: C. Organophosphate insecticides

   Nerve agents are organophosphate compounds far more potent than farm insecticides, and both inhibit acetylcholinesterase. Cyanide is a metabolic poison that blocks cell oxygen use, not acetylcholine breakdown.

2. Of the nerve agents, the one that is an oily liquid, evaporates slowly, and stays on surfaces for days is:

   1. A. Sarin, a G-series agent
   2. B. VX, a V-series agent
   3. C. Soman, a G-series agent
   4. D. Tabun, a G-series agent
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   Answer: B. VX, a V-series agent

   VX is the least volatile and most persistent nerve agent, so it is mainly a skin contact hazard. Sarin is the opposite: it evaporates quickly and is mainly an inhalation threat.

3. Sarin poses mainly an inhalation hazard because it:

   1. A. Sticks to skin as a thick oil
   2. B. Releases spores as it dries out
   3. C. Forms crystals that are swallowed
   4. D. Evaporates quickly into a vapor
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   Answer: D. Evaporates quickly into a vapor

   Sarin is highly volatile, so a liquid release quickly becomes a vapor cloud that is inhaled, as in the Tokyo subway attack. Persistence on skin as an oil describes VX.

4. After soman exposure, pralidoxime must be given within minutes because the agent-enzyme bond:

   1. A. Breaks apart on its own in minutes
   2. B. Ages and becomes permanent quickly
   3. C. Reaches the heart muscle in minutes
   4. D. Turns into cyanide within minutes
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   Answer: B. Ages and becomes permanent quickly

   Pralidoxime can pull a nerve agent off acetylcholinesterase only before the bond 'ages'; soman ages in about 2 minutes, compared with hours for sarin and VX. The bond does not break on its own, which is why the body must make new enzyme over weeks.

5. The most common sign of exposure to nerve agent vapor, even at low doses, is:

   1. A. Dilated pupils (mydriasis)
   2. B. Generalized seizures
   3. C. Pinpoint pupils (miosis)
   4. D. A slow heart rate
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   Answer: C. Pinpoint pupils (miosis)

   Vapor acts directly on the eyes, so miosis with dim or blurred vision appears even after small exposures. Bradycardia is often absent because nicotinic and hypoxic effects can push the heart rate up.

6. A soldier had a drop of VX on his forearm 2 hours ago and now has sweating and muscle twitching at that site only. This pattern shows that a liquid skin exposure:

   1. A. Can cause delayed, local signs first
   2. B. Rarely leads to systemic poisoning
   3. C. Shows the agent on his skin has worn off
   4. D. Is harmless once the skin is dry
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   Answer: A. Can cause delayed, local signs first

   Liquid nerve agent is absorbed slowly through the skin, so sweating and twitching at the contact site often come first, and systemic signs may be delayed up to about 18 hours. A droplet of VX can be fatal, so systemic poisoning is not rare. Local signs mean agent is still being absorbed, not that it has worn off. Dry skin does not make him safe, because the agent has already penetrated. He needs decontamination and close observation.

7. In severe nerve agent poisoning, death most often results from:

   1. A. Ventricular fibrillation
   2. B. Acute liver failure
   3. C. Respiratory failure
   4. D. Massive hemorrhage
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   Answer: C. Respiratory failure

   Bronchorrhea, bronchospasm, paralysis of the breathing muscles, and loss of central respiratory drive combine to stop ventilation. Dysrhythmias can occur but are not the usual cause of death.

8. A 30-year-old man at a sarin release has pinpoint pupils, a runny nose, and mild chest tightness but is walking and talking clearly. Using DuoDote, you should give:

   1. A. Three autoinjectors in rapid succession
   2. B. One autoinjector, then watch for worsening
   3. C. No autoinjector until seizures develop
   4. D. Two autoinjectors given about 30 minutes apart
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   Answer: B. One autoinjector, then watch for worsening

   Mild signs call for one DuoDote, with two more in rapid succession if severe signs develop. Three at once is the dose for severe poisoning, and waiting for seizures lets hypoxia and secretions worsen.

9. Ten minutes after one DuoDote for mild signs, a sarin victim becomes confused, with heavy secretions and diffuse twitching. You should now:

   1. A. Give two more autoinjectors in rapid order
   2. B. Wait 30 more minutes before giving a second dose
   3. C. Switch to pralidoxime by IV push
   4. D. Give three more for a total of four
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   Answer: A. Give two more autoinjectors in rapid order

   Progression to severe signs calls for two more DuoDote injections for a total of three. Giving three more exceeds the field maximum of three; further atropine comes from medical direction.

10. A DuoDote autoinjector should be given into the:

    1. A. Deltoid, after removing the shirt
    2. B. Abdomen, 5 cm (2 in) away from the navel
    3. C. Upper inner quadrant of the buttock
    4. D. Outer thigh, through clothing if needed
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    Answer: D. Outer thigh, through clothing if needed

    The mid-outer thigh has large muscle mass, and the needle works through clothing, so no time is lost undressing; hold it in place about 10 seconds. The deltoid is too small and needs the shirt removed.

11. After three DuoDote injections, a sarin victim still has heavy bronchial secretions and wheezing. Per medical direction, the drug most often repeated is:

    1. A. Pralidoxime, 600 mg every 5 minutes
    2. B. Midazolam, 10 mg IM every 5 minutes
    3. C. Atropine, about 2 mg every 5 to 10 min
    4. D. Epinephrine, 0.5 mg IM every 5 minutes
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    Answer: C. Atropine, about 2 mg every 5 to 10 min

    Additional atropine in 2-mg doses is repeated until secretions dry and breathing eases; large total doses may be needed. Pralidoxime is not repeated that fast because of its limited benefit at high doses and risk of side effects such as hypertension.

12. A nerve agent victim begins seizing after receiving three DuoDote injections. The preferred anticonvulsant in the field is:

    1. A. Atropine 2 mg IM until the seizure stops
    2. B. Pralidoxime 1 g by slow IV push
    3. C. Diphenhydramine 50 mg IM or IV
    4. D. Midazolam 10 mg IM by autoinjector
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    Answer: D. Midazolam 10 mg IM by autoinjector

    A benzodiazepine is needed to stop nerve agent seizures, and a midazolam 10 mg autoinjector is approved for this use in adults. Atropine is tempting, but once seizures begin, atropine alone does not stop them.

13. A sarin victim with severe signs has received three DuoDote kits and was intubated after rocuronium. He now lies still. Regarding nerve agent seizures, you should know that:

    1. A. Rocuronium also stops the seizure activity
    2. B. They may continue with no visible jerking
    3. C. They end once the secretions have dried
    4. D. Pralidoxime has already prevented them
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    Answer: B. They may continue with no visible jerking

    Rocuronium blocks the neuromuscular junction, so it stops visible jerking but not the electrical seizure in the brain; in a paralyzed nerve agent victim, seizures can continue unseen and keep injuring the brain. Severe poisoning therefore calls for a benzodiazepine per protocol or medical direction, and the hospital may use EEG to confirm control. Dry secretions show that atropine has blocked muscarinic effects, which says nothing about seizure control. Pralidoxime acts mainly outside the brain and does not prevent nerve agent seizures.

14. A sarin victim with heavy secretions has a heart rate of 128 beats/min. Your partner says atropine is unsafe at this rate. You should:

    1. A. Give atropine; the rate is no reason to hold it
    2. B. Hold the atropine until the rate is under 100
    3. C. Give a beta blocker first to slow the heart rate
    4. D. Give pralidoxime and skip the atropine
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    Answer: A. Give atropine; the rate is no reason to hold it

    Tachycardia in nerve agent poisoning is common from hypoxia, fear, and nicotinic stimulation, and it often improves as atropine clears the airways. Holding atropine for tachycardia lets the patient drown in secretions.

15. You must intubate a nerve agent victim. Succinylcholine should be avoided because:

    1. A. Its paralysis may last far longer
    2. B. It worsens bronchospasm right away
    3. C. It binds the nerve agent in the blood
    4. D. It cannot be given through an IO line
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    Answer: A. Its paralysis may last far longer

    Succinylcholine is broken down by plasma cholinesterase, which nerve agents inhibit, so paralysis can be greatly prolonged; a nondepolarizing agent such as rocuronium is preferred. Bronchospasm is caused by the agent, not by succinylcholine.

16. While working near a sarin release, you develop a runny nose, tight chest, and blurred vision. You should first:

    1. A. Finish the triage first, then report your symptoms
    2. B. Give yourself three DuoDote right away
    3. C. Wait in fresh air for the signs to pass
    4. D. Leave the area and give yourself one DuoDote
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    Answer: D. Leave the area and give yourself one DuoDote

    A responder with mild signs should get out of the hazard and use self-aid with one autoinjector, then report. Three at once is for severe signs, which you do not have.

17. Pyridostigmine bromide tablets taken by soldiers before a possible soman attack act as a:

    1. A. Treatment once symptoms have begun
    2. B. Pretreatment that aids later antidotes
    3. C. Vaccine that blocks the absorption of agent
    4. D. Replacement for pralidoxime kits
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    Answer: B. Pretreatment that aids later antidotes

    Pyridostigmine temporarily shields some acetylcholinesterase from soman's rapid aging, making the antidotes given after exposure work better. It is not a treatment after symptoms start, and it can worsen signs if taken after exposure.

18. A responder exposed to low levels of sarin vapor has only pinpoint pupils and dim vision, with no other signs. The best plan is to:

    1. A. Give one DuoDote at once to treat the vision change
    2. B. Give three DuoDote to prevent seizures
    3. C. Monitor him; miosis alone needs no autoinjector
    4. D. Give pralidoxime to fix the pupils
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    Answer: C. Monitor him; miosis alone needs no autoinjector

    Isolated miosis from vapor is a local eye effect and does not call for autoinjectors; injected atropine does little for it. One DuoDote is indicated when two or more mild systemic signs appear.

19. During the 1995 Tokyo subway sarin attack, many hospital staff developed symptoms. The main cause was:

    1. A. Sarin moving through hospital ducts
    2. B. Person-to-person spread by coughing
    3. C. Contaminated antidote vials
    4. D. Off-gassing from victims' clothes
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    Answer: D. Off-gassing from victims' clothes

    Victims who arrived without decon carried sarin on clothing and hair, and the vapor sickened staff in poorly ventilated areas. Nerve agents are poisons, not infections, so they do not spread by coughing.

20. A sarin victim is barely breathing, with heavy secretions and wheezing, and bag-mask ventilation meets high resistance. The step most likely to make ventilation easier is:

    1. A. Faster bagging at about 30 breaths per minute
    2. B. Atropine to dry secretions and ease wheezing
    3. C. A nebulized bronchodilator in place of atropine
    4. D. Suctioning while holding the atropine
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    Answer: B. Atropine to dry secretions and ease wheezing

    Airway resistance in nerve agent poisoning comes from bronchorrhea and bronchospasm, both muscarinic effects that atropine reverses; ventilation usually becomes easier once enough atropine is given (by IM autoinjector while the patient is still hypoxic), and atropine is repeated until ventilation resistance and secretions fall. Faster bagging raises airway pressure and gastric inflation without fixing the cause. A nebulized bronchodilator may ease some bronchospasm but does nothing for the secretions and cannot replace atropine. Suctioning helps briefly, but secretions keep forming until atropine is given, so atropine must not be held.

21. Novichok agents, used in the 2018 poisoning in Salisbury, England, are best described as:

    1. A. Blister agents like mustard
    2. B. Choking agents similar to phosgene
    3. C. Nerve agents more potent than VX
    4. D. Biologic toxins from castor beans
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    Answer: C. Nerve agents more potent than VX

    Novichoks are a newer class of organophosphate nerve agents, reported to be more potent than VX, and they are treated with the same antidotes and supportive care. The castor bean toxin is ricin, which is a biologic toxin with no antidote.

22. Nerve agent vapors such as sarin are heavier than air, so they tend to:

    1. A. Collect in low areas such as subways
    2. B. Rise and disperse quickly above the crowd
    3. C. Stay in liquid form on the ground
    4. D. Break down within a few seconds
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    Answer: A. Collect in low areas such as subways

    Heavier-than-air vapors pool in basements, stairwells, and subway tunnels, so victims and crews should move to higher ground. Rapid breakdown would make sarin far less dangerous than it is.

23. At a stadium, dozens of people collapse within minutes of a mist release. Which finding most suggests a nerve agent rather than cyanide?

    1. A. Seizures and a sudden collapse to the ground
    2. B. Rapid breathing and confusion
    3. C. Pinpoint pupils with heavy secretions
    4. D. Fast onset after inhaling a gas
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    Answer: C. Pinpoint pupils with heavy secretions

    Miosis with copious secretions is the cholinergic signature of nerve agents. Seizures, sudden collapse, and rapid onset after inhalation occur with both nerve agents and cyanide, so they do not tell them apart.

24. A man who was given two DuoDote injections by a coworker is now hot, flushed, and confused, with dry skin, a heart rate of 150 beats/min, and clear lungs with no twitching. This suggests:

    1. A. Worsening nerve agent poisoning
    2. B. Cyanide toxicity hidden by the atropine
    3. C. An allergy to pralidoxime
    4. D. Too much atropine for the exposure
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    Answer: D. Too much atropine for the exposure

    Dry, flushed skin, tachycardia, and confusion with clear lungs and no fasciculations are anticholinergic effects from atropine given beyond what his exposure needed. Worsening nerve agent toxicity would bring secretions and twitching, not dryness.

25. A cyanotic nerve agent victim with heavy secretions needs atropine. Giving it IV before the patient is oxygenated is a concern because:

    1. A. IV atropine will not reach the lungs
    2. B. A hypoxic heart may fibrillate
    3. C. Atropine must first be mixed with oxime
    4. D. IV atropine blocks the oxime
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    Answer: B. A hypoxic heart may fibrillate

    Atropine given IV to a severely hypoxic heart can trigger ventricular fibrillation, so ventilate and oxygenate first or give it IM, which is how autoinjectors deliver it. Atropine reaches the airways well by any route, so poor delivery is not the reason.