What is Nerve Agents?
Nerve agents, which are harmful substances, play a big role in causing sickness and death in emergency medical situations involving poisoning. People affected by nerve agents mainly show symptoms due to an overproduction of a chemical named acetylcholine in their bodies. This can lead to increased fluid secretions in the body, difficulty in breathing, and paralysis.
To diagnose these cases, doctors have to rely mainly on the symptoms shown by the patient. The treatment for this usually involves making the patient as comfortable as possible and providing supportive care immediately, along with the use of two specific antidotes known as atropine and pralidoxime.
As such, doctors need to be very familiar with nerve agents to correctly diagnose and treat patients suffering from this deadly type of poisoning.
What Causes Nerve Agents?
Nerve agent toxicity primarily happens due to exposure from the environment. There are different ways people can come into contact with these nerve agents. For example, those who work in agriculture or industrial settings might be exposed to certain chemicals found in insecticides called organophosphates and carbamates.
Some nerve agents are synthetic, meaning they are man-made. Examples include soman, tabun, sarin, and VX, which have been used in harmful acts of biowarfare, both in history and in recent times.
Soman is a nerve agent that was created in Germany during World War II but was never actually used in the war. Tabun is a type of organophosphorus compound. It was also developed in Germany and there were reports that it was planned to be used in an assassination plot against Adolf Hitler.
Sarin is a highly potent nerve agent. It is so dangerous that it can cause death from paralysis of the respiratory system in just 1 to 10 minutes. In a shocking case, it was used in a 1995 attack on the Tokyo subway system, leading to the deaths of 12 people. VX is another synthetic nerve agent, and in a notable case, it was used in the assassination of Kim Jong Nam, the half-brother of North Korean leader Kim Jong Un, in February 2017.
Risk Factors and Frequency for Nerve Agents
Each year, over 10,000 people in the United States and 3 million people worldwide are affected by toxicity from organophosphates and carbamates. These substances, which are found in insecticides, herbicides, rodenticides, and even chemical warfare agents like soman, sarin, tabun, and VX, cause up to 300,000 deaths annually. There are various situations where exposure to these nerve damaging agents can occur, including agricultural accidents, biowarfare, and in certain industries.
- Organophosphates and carbamates affect over 10,000 people in the United States and 3 million people worldwide every year.
- These substances are found in insecticides, herbicides, rodenticides, and chemical warfare agents.
- They cause up to 300,000 deaths each year.
- The primary situations where these toxicities occur are agricultural accidents, in cases of biowarfare and within certain industries.
Signs and Symptoms of Nerve Agents
Nerve agent toxicity happens when certain harmful substances excessively stimulate parts of the nervous system. This results in a number of clear symptoms, often labeled under the acronym DUMBELS. These symptoms include:
- Defecation (going to the toilet excessively)
- Urination
- Muscle weakness
- Miosis (narrowing of the pupils)
- Bradycardia (slow heart rate)
- Bronchospasm (tightening of the airway muscles)
- Bronchorrhea (production of more than 100 ml of sputum per 24 hours)
- Emesis (throwing up)
- Lacrimation (excessive tear production)
- Salivation (excess saliva)
A substance known as ACh also attaches to certain receptors in our body during nerve agent toxicity, causing muscle twitches, cramps, weakness, paralysis, and loss of reflexes. When ACh stimulates the brain, it can cause seizures or even coma. Because nerve agent toxicity affects every organ system in our body, it can cause various signs and symptoms. This might make it difficult to diagnose. Patients often become extremely sick soon after exposure.
Testing for Nerve Agents
The process of diagnosing the condition typically relies more on physical check-ups and symptoms, as lab tests specific to this condition often take too long and may not accurately detect the disease. However, testing cholinesterase levels in the body can be helpful as it can predict the disease and its potential outcomes. In particular, analyzing red blood cell (RBC) Acetylcholinesterase (AChE) can provide more details about the severity of the disease and whether additional treatment may be necessary. Follow-up tests on RBC-AChE will show how well the patient is responding to treatment over time.
While routine lab tests may not always yield significant results, they could help rule out other potential conditions and guide treatment options. If a doctor suspects the condition based on symptoms, a trial of atropine (a kind of medication) could be used to see if the patient’s condition improves. The dosage is typically 1 mg for adults and 0.01 mg/kg for children.
Treatment Options for Nerve Agents
The main aim of treatment for acute nerve agent exposure is to provide essential supportive care. This might include assisting with breathing, monitoring heart activity, removing any remaining nerve agent from the body, and giving specific antidotes to counteract the nerve agent’s effects. It’s important that healthcare workers use personal protective equipment to prevent exposure to the nerve agent through the skin, which could be harmful.
Atropine is normally used as the primary antidote in cases of nerve agent poisoning. It works by blocking the effects of a chemical called acetylcholine at the junction between nerves and muscles.
Alongside atropine, oximes like pralidoxime can be used. These drugs help to remove the nerve agent from an enzyme called acetylcholinesterase, allowing the enzyme to start working properly again. This is important in the early stages of nerve agent toxicity, to help prevent further deterioration of the condition.
The biggest risk from nerve agents is respiratory failure due to paralysis. Because of this, it’s essential to ensure breathing support is provided, which could include the use of a ventilator machine.
People affected by nerve agent poisoning need ongoing monitoring, especially of their heart function. Acetylcholine can slow the heart rate, and it can potentially extend the amount of time between electrical signals in the heart. This could lead to a rapid heart rate, which may need to be treated with shock therapy or medications like amiodarone if the person’s condition is stable. If it involves an extension of the time between heart signals, a treatment involving intravenous magnesium could be needed.
Nerve agent poisoning often leads to excessive secretions, which may require insertion of a breathing tube. If this is necessary, it’s important not to use a certain type of muscle relaxant drug called succinylcholine because the nerve agent will interfere with its breakdown, causing it to act for longer than intended. Other muscle relaxants like rocuronium that do not have this issue could be used instead.
Seizures are a common issue with nerve agent poisoning. Medications like benzodiazepines are generally the first choice of treatment for these. Usual anti-seizure medications such as levetiracetam and fosphenytoin may be less effective, but could be used if the benzodiazepines aren’t stopping the seizures.
What else can Nerve Agents be?
Diagnosing nerve agent toxicity can be challenging, especially if there’s no known history of exposure to the agent. There’s a long list of potential diagnoses that could have similar symptoms. For instance, an overdose of certain medications, like physostigmine or edrophonium which are known as acetylcholinesterase inhibitors, may present similar symptoms.
Besides these, there are also other poisonous substances or toxins that can show the same signs. Infections could likewise cause symptoms that appear alike to cholinergic toxicity. It’s crucial for a healthcare provider to take all these possibilities into account. They must then carry out necessary blood work and imaging studies, whenever they see the need, to rule out any other causes.
What to expect with Nerve Agents
The outlook of nerve agent poisoning can depend on a few things such as what specific nerve agent was involved, how much exposure there was, how the patient was exposed (for example, through skin contact or inhalation), and how long the exposure lasted. The Glasgow Coma Score (GCS), which is a medical scale used to measure a patient’s state of consciousness, is sometimes used to predict the outcome. A score below 13 on this scale usually indicates a bad prognosis.
The Poisoning Severity Scale used to be used to determine the prognosis, but nowadays other scoring systems are considered more accurate. These include the Acute Physiology and Chronic Health Evaluation II (APACHE-II), the Simplified Acute Physiology Score II (SAPS-II), and the Mortality Prediction Model II (MPM-II). These systems have proven to be better in predicting death in several studies.
Possible Complications When Diagnosed with Nerve Agents
: Improper dosage of a drug called oximes can cause a condition known as intermediate syndrome in patients who have been poisoned by chemicals known as organophosphates. This syndrome typically appears 24 to 96 hours after exposure to the chemicals and is marked by symptoms such as reduced reflexes, shallow breathing, weakness in muscles near the body’s center (like the chest and thighs), and issues with the nerves in the head that control senses and movements (cranial nerves).
Apart from this, patients might still face complications one to three weeks after exposure. A condition known as Organophosphorous agent-induced delayed neuropathy (OPIDN), mostly targets muscle groups located far from the center of the body, like the hands and feet. It is known for causing symptoms like painful numbness and weakness in the lower body, especially in a pattern that resembles wearing a stocking or glove. Interestingly, OPIDN is not linked to the initial poisonous effect of the organophosphates, which affects major body functions through a substance called cholinergic toxicity.
If doctors suspect a case of OPIDN, they should seek the advice of a neurologist (nerve specialist) and plan for regular checkups.
Common Symptoms:
- Reduced reflexes
- Shallow breathing
- Weakness in muscles near the body’s center
- Issues with the cranial nerves
- Painful numbness and weakness in the lower body
