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Threat Scenario ~ Detection ~ Super Diseases ~ Bio-Terror |
Weapons of Mass Destruction (Chem/Bio)
BZ Gas, Anthrax, Botulism, Ebola, Glanders, Hantavirus, Pneumonic Plague, SmallPox, Tularemia, Typhoid, VX Gas Nerve Agents:Tabun-Sarin-Soman ~ Tokyo ~ Retaliation ~ Al Qaeda Terrorist Manual
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VX Gas or VX VaporIraq, for example, was at one time an admitted producer of 3.9 tons of VX . Syria is believed to have its advanced (with North Korean guidance technology) SCUD-D missiles equipped with VX warheads aimed at Israel. VX is a nerve agent involving organic phosphorous compounds and sulphur. It works essentially by penetrating the skin and disrupting the transmission of nerve impulses.
VX gas is one of the most dangerous chemicals created by man.VX gas is an aerosoled chemical warfare agent derived from the oil-based VX. In the film “The Rock”, it was that green liquid that the terrorists threatened San Francisco Bay with. VX gas was developed in the Porton Down Chemical Weapons Research Centre, Wiltshire, England in 1952 and its devastating effects were tested. The British traded the technology of VX with the United States of America for information on thermonuclear weapons. Its chemical formula is CH3CH20-P(O)(CH3)-SCH2CH2N(C3H7)2 and is normally in its liquid state despite its name. It has a low volatility; is odourless and is an excellent adhesive. A special form has been developed that is so adhesive that it is virtually impossible to remove from the surface that it is in contact with. This leads to strategic attacks on enemy bases or airfields so that the VX remains stuck to the area and has the potential to kill any one attempting to use the base or airfield. The “V” of VX signifies it long persistence. So it is more dangerous and toxic than its cousins of the “G” variety like GA (Tabun) and GB (Sarin), which dissipate quickly and have only short-term effects. In the liquid form of VX, it is absorbed through the eyes or the skin of the victim. It takes an hour or two to take effect and its effects result in death. The gaseous form is more deadly than the liquid form and acts almost immediately on the victim. The effects are worst when it is inhaled and death is an end to the suffering. The LD50 can be as little as 10mg for humans. It operates by cutting off the nervous system. It binds to the enzyme that transmits signals to the nerves and inhibits them. Therefore the nerves become isolated and uncontrollable. The antidote, atropine, is a toxin itself but it counteracts the effect of the VX by removing it from the enzyme. It is an anti-nerve agent so does the reverse of the VX, a nerve agent. It is normally injected into the arm or thigh but for gaseous attacks the atropine must go immediately into the heart. So full body protection and gas masks are essential to avoid exposure in a VX missile attack. VX has not been used to its fullest potential yet because it is too dangerous to use for local attacks with wind that could blow the VX back onto the base. This factor has helped to keep VX from being used to cripple local nations. If these weapons were launched against a nation then there would be the possibility of a nuclear counterattack because VX is a weapon of mass destruction that spreads from impact point killing all in its path. This would be countered by another, which in a lot of cases, would be a nuclear bomb. The only known countries to possess VX are U.S. France and Russia. England after inventing it abandoned the thought for thermonuclear warfare. Victims who inhale VX should also be given access to fresh air. Those whose skin has touched VX should be washed with soap and water. Another chemical, pyridostigmine bromide, can be given before exposure to increase resistance to VX. How does VX compare to sarin gas or mustard gas? Mustard gas, a blister agent, is less deadly than both VX and sarin but can lead to more lasting health effects, such as cancer and birth defects.
Other Nerve AgentsNerve Agents Tabun (GA) 77-81-6
Sarin (GB) 107-44-8 Soman (GD) 96-64-0 VX 50782-69-9 HISTORY/MILITARY RELEVANCE Table I
Vapor toxicity
mg-min/m3
Table II
LD50on skin
GB, the agent studied most thoroughly in man, will cause miosis, rhinorrhea, and a feeling of tightness in the throat or chest at a Ct of 3 to 5 mg·min/m3. Effects: Exposure to a small amount of nerve agent vapor causes effects in the eyes, nose, and airways. These effects are from local contact of the vapor with the organ and do not indicate systemic absorption of the agent. In this circumstance, the erythrocyte-ChE may be normal or depressed. A small amount of liquid agent on the skin causes systemic effects initially in the gastrointestinal (GI) tract. Lethal amounts of vapor or liquid cause a rapid cascade of events culminating within a minute or two with loss of consciousness and convulsive activity followed by apnea and muscular flaccidity within several more minutes. Eye: Miosis is a characteristic sign of exposure to nerve agent vapor. It occurs as a result of direct contact of vapor with the eye. Liquid agent on the skin will not cause miosis if the amount of liquid is small; a moderate amount of liquid may or may not cause miosis; and a lethal or near-lethal amount of agent usually causes miosis. A droplet of liquid in or near the eye will also cause miosis. Miosis will begin within seconds or minutes after the onset of exposure to agent vapor, but it may not be complete for many minutes if the vapor concentration is low. Miosis is bilateral in an unprotected individual, but occasionally may be unilateral in a masked person with a leak in his mask eyepiece. Miosis is often accompanied by complaints of pain, dim vision, blurred vision, conjunctival injection, nausea, and occasionally vomiting. The pain may be sharp or dull in or around the eyeball, but more often is a dull ache in the frontal part of the head. Dim vision is due in part to the small pupil, and cholinergic mechanisms in the visual pathways also contribute. The complaint of blurred vision is less easily explained, as objective testing usually indicates an improvement in visual acuity because of the “pin-hole” effect. Conjunctival injection may be mild or severe, and occasionally subconjunctival hemorrhage is present. Nausea (and sometimes vomiting) are part of a generalized complaint of not feeling well. Miosis, pain, dim vision, and nausea can be relieved by topical homatropine or atropine in the eye. Nose: Rhinorrhea may be the first indication of nerve agent vapor exposure. Its severity is dose dependent. Airways: Nerve agent vapor causes bronchoconstriction and increased secretions of the glands in the airways in a dose-related manner. The exposed person may feel a slight tightness in his chest after a small amount of agent and may be in severe distress after a large amount of agent. Cessation of respiration occurs within minutes after the onset of effects from exposure to a large amount of nerve agent. This apnea is probably mediated through the CNS, although peripheral factors (skeletal muscle weakness, e.g., the intercostal muscles, and bronchoconstriction) may contribute. Gastrointestinal tract: After they are absorbed, nerve agents cause an increase in the motility of the GI tract and an increase in secretions by the glands in the wall of the GI tract. Nausea and vomiting are early signs of liquid exposure on the skin. Diarrhea may occur with large amounts of agent. Glands: Nerve agent vapor causes increases in secretions from the glands it contacts, such as the lacrimal, nasal, salivary, and bronchial glands. Localized sweating around the site of liquid agent on the skin is common, and generalized sweating after a large liquid or vapor exposure is common. Increased secretions of the glands of the GI tract occur after systemic absorption of the agent by either route. Skeletal Muscle: The first effect of nerve agents on skeletal muscle is stimulation producing muscular fasciculations and twitching. After a large amount of agent, fatigue and weakness of muscles are rapidly followed by muscular flaccidity. Fasciculations are sometimes seen early at the site of a droplet of liquid agent on the skin, and generalized fasciculations are common after a large exposure. These may remain long after most of the other acute signs decrease. Central Nervous System: The acute CNS signs of exposure to a large amount of nerve agent are loss of consciousness, seizure activity, and apnea. These begin within a minute after exposure to a large amount of agent vapor and may be preceded by an asymptomatic period of one to 30 minutes after contact of liquid with the skin. After exposure to smaller amounts of nerve agents, CNS effects vary and are nonspecific. They may include forgetfulness, an inability to concentrate fully, insomnia, bad dreams, irritability, impaired judgement, and depression. They do not include frank confusion and misperceptions (i.e., hallucinations). These may occur in the absence of physical signs or other symptoms of exposure. After a severe exposure these symptoms occur upon recovery from the acute severe effects. In either case they may persist for as long as four to six weeks. Cardiovascular: The heart rate may be decreased because of stimulation by the vagus nerve, but it is often increased because of other factors, such as fright, hypoxia, and the influence of adrenergic stimulation secondary to ganglionic stimulation. Thus, the heart rate may be high, low, or in the normal range. Bradyarrhythmias, such as first-, second-, or third-degree heart block may occur. The blood pressure may be elevated from adrenergic factors, but is generally normal until the terminal decline. PHYSICAL FINDINGS Physical findings depend on the amount and route of exposure. After exposure to small to moderate amounts of vapor, there are usually miosis and conjunctival injection, rhinorrhea, and pulmonary signs, although the latter may be absent even in the face of mild to moderate pulmonary complaints. In addition to these signs, an exposure to a high Ct may precipitate copious secretions from the nose and mouth, generalized muscular fasciculations, twitching or seizure activity, loss of consciousness, and apnea. Cyanosis, hypotension, and bradycardia may be present just before death. Exposure to a small droplet of liquid on the skin may produce few physical findings. Sweating, blanching, and occasionally fasciculations at the site may be present soon after exposure, but may no longer be present at the onset of GI effects. After a large exposure, the signs are the same as after vapor exposure. Miosis is a useful sign of exposure to vapor, but does not occur after a liquid exposure unless the amount of exposure is large or the exposure is in or close to the eye. TIME COURSE OF EFFECTS Effects from nerve agent vapor begin within seconds to several minutes after exposure. Loss of consciousness and onset of seizure activity have occurred within a minute of exposure to a high Ct. After exposure to a very low Ct, miosis and other effects may not begin for several minutes, and miosis may not be complete for 15 to 30 minutes after removal from the vapor. There is no latent period or delay in onset from vapor exposure. Effects may continue to progress for a period of time, but maximal effects usually occur within minutes after exposure stops. A large amount of liquid on the skin causes effects within minutes. Commonly there is an asymptomatic period of one to 30 minutes, and then the sudden onset of an overwhelming cascade of events, including loss of consciousness, seizure activity, apnea, and muscular flaccidity. After small amounts of liquid agent on the skin the onset of effects has been delayed for as long as 18 hours after contact. These effects are initially gastrointestinal and are usually not life threatening. Generally, the longer the interval the less severe are the effects. DIFFERENTIAL DIAGNOSIS The effects caused by a mild vapor exposure, namely rhinorrhea and a tightness in the chest, may easily be confused with an upper respiratory malady or an allergy. Miosis, if present, will help to distinguish these, but the eyes must be examined in very dim light to detect this. Similarly, GI symptoms from another illness may be confused with those from nerve agent effects, and in this instance there will be no useful physical signs. History of possible exposure will be helpful, and laboratory evidence (decreased RBC-ChE activity), if available, will be useful to distinguish the two. The diagnosis is easier in the severely intoxicated patient. The combination of miosis, copious secretions, and generalized muscular fasciculations in a gasping, cyanotic, and convulsing patient is characteristic. LABORATORY FINDINGS The cholinesterase activity of the blood components is inhibited by nerve agents, and estimation of this activity is useful in detecting exposure to these agents. The erythrocyte enzyme activity is more sensitive to acute nerve agent exposure than is the plasma enzyme activity. The amount of inhibition of this enzyme activity does not correlate well with the severity of local effects from mild to moderate vapor exposure. The enzyme activity may be from 0% to 100% of the individual’s normal activity in the face of miosis, rhinorrhea, and/or airway symptoms. Normal or nearly normal erythrocyte acetylcholinesterase activity may be present with moderate effects in these organs. At the other extreme, the enzyme may be inhibited by 60% to 70% when miosis or rhinorrhea is the only sign of exposure. Severe systemic effects generally indicate inhibition of the erythrocyte acetylcholinesterase by 70% to 80% or greater. Other laboratory findings will relate to complications. For example, acidosis may occur after prolonged hypoxia. MEDICAL MANAGEMENT Management of a casualty with nerve agent intoxication consists of decontamination, ventilation, administration of the antidotes, and supportive therapy. The condition of the patient dictates the need for each of these and the order in which they are done. Decontamination is described elsewhere in this manual. Skin decontamination is not necessary after exposure to vapor alone, but clothing should be removed because it may contain “trapped” vapor. The need for ventilation will be obvious, and the means of ventilation will depend on available equipment. Airway resistance is high (50-70 cm of water) because of bronchoconstriction and secretions, and initial ventilation is difficult. The resistance decreases after atropine administration, after which ventilation will be easier. The copious secretions, which may be thickened by atropine, also impede ventilatory efforts and require frequent suctioning. In reported cases of severe nerve agent exposure, ventilation has been required from 0.5 to 3 hours. Three drugs are used to treat nerve agent exposure, and another is used as pretreatment for potential nerve agent exposure. The three therapeutic drugs are atropine, pralidoxime chloride, and diazepam. The use of the pretreatment drug, pyridostigmine bromide, is discussed later in this chapter. Atropine is a cholinergic blocking, or anticholinergic, compound. It is extremely effective in blocking the effects of excess acetylcholine at peripheral muscarinic sites. Under experimental conditions, very large amounts may block some cholinergic effects at nicotinic sites, but these antinicotinic effects are not evident even at high clinical doses. When small amounts (2 mg) are given to normal individuals without nerve agent intoxication, atropine causes mydriasis, a decrease in secretions (including a decrease in sweating), mild sedation, a decrease in GI motility, and tachycardia. The amount in three MARK I kits may cause adverse effects on military performance in a normal person. In people not exposed to nerve agents, amounts of 10 mg or higher may cause delirium. Potentially, the most hazardous effect of inadvertent use of atropine (2 mg, i.m.) in a young person not exposed to a cholinesterase inhibiting compound in a warm or hot atmosphere is inhibition of sweating, which may lead to heat injury. In the military, atropine is packaged in autoinjectors, each containing 2 mg. Pralidoxime chloride (Protopam chloride; 2-PAMCl) is an oxime. Oximes attach to the nerve agent that is inhibiting the cholinesterase and break the agent-enzyme bond to restore the normal activity of the enzyme. Clinically, this is noticable in those organs with nicotinic receptors. Abnormal activity in skeletal muscles decreases, and normal strength returns. The effects of an oxime are not apparent in organs with muscarinic receptors; oximes do not cause a decrease in secretions, for example. They also are less useful after aging occurs, but with the exception of GD (soman) intoxicated individuals, casualties will be treated before significant aging occurs. Pralidoxime chloride (600 mg) is in an autoinjector for self-use along with the atropine injector. These atropine and pralidoxime chloride autoinjectors are packaged together in a MARK I kit. Each military person is issued three MARK I kits. Diazepam is an anticonvulsant drug used to decrease convulsive activity and to reduce the brain damage caused by prolonged seizure activity. Without the use of pyridostigmine pretreatment, experimental animals died quickly after superlethal doses of nerve agents despite conventional therapy. With pyridostigmine pretreatment (followed by conventional therapy) animals survived superlethal doses of soman, but had prolonged periods of seizure activity before recovery. They later had performance decrements and anatomic lesions in their brains. The administration of diazepam with other standard therapy to soman-poisoned animals pretreated with pyridostigmine reduced the seizure activity and its sequelae. Current military doctrine is to administer diazepam with other therapy (three MARK I’s) at the onset of severe effects from a nerve agent, whether or not seizure activity is among those effects. Each military person carries one autoinjector containing 10 mg of diazepam for his buddy to administer to him (if he could self-administer it, he would not need it). Diazepam should be administered with the three MARK I’s when the casualty’s condition warrants the use of three MARK I’s at the same time. Medical personnel can administer more diazepam to a casualty if necessary. The medical corpsman carries extra diazepam injectors and is authorized to administer two additional injectors at 10 minute intervals to a convulsing casualty. The doctrine for self-aid for nerve agent intoxication states that if an individual has effects from the agent he/she should self-administer one MARK I. If there is no improvement in 10 minutes, he/she should seek out a buddy to assist in the evaluation of his/her condition before further MARK I’s are given. If a buddy finds an individual severely intoxicated (e.g., gasping respirations, twitching, etc.) so that the individual can not self-administer a MARK I, the buddy should administer three MARK I’s and diazepam immediately. The discussion below is advice for medical assistance. The appropriate number of MARK I kits to administer initially to a casualty from nerve agent vapor depends on the severity of the effects. Systemic atropine will not reverse miosis (unless administered in very large amounts), and miosis alone is not an indication for a MARK I. If the eye or head pain and nausea associated with the miosis are severe, topical application of atropine (or homatropine) in the eye will bring relief. Topical atropine should not be used without good reason (severe pain), because it causes blurred vision for a day or longer. A casualty with miosis and rhinorrhea should be given one MARK I only if the rhinorrhea is severe and troublesome (he can not keep his mask on because of fluid). A casualty with mild to moderate dyspnea should be given one or two MARK I’s, depending on the severity of his distress and the time between exposure and therapy. Some of the respiratory distress from a mild exposure will spontaneously decrease within 15 to 30 minutes after termination of exposure, so if the casualty is not severely uncomfortable only one MARK I should be used initially. Atropine is quite effective, and care should be taken not to give too much in a casualty who does not need it. A severe casualty from nerve agent vapor has miosis, copious secretions from the nose and mouth, severe difficulty breathing or apnea, possibly some degree of cyanosis, muscular fasciculations, and twitching or convulsive activity, and is unconscious. He should be given three MARK I’s and diazepam immediately. Ventilation will be needed and should be done via an endotracheal airway if possible. Suctioning of the excessive airway secretions will be necessary to enhance air exchange and will make ventilatory efforts easier. Atropine, 2 mg, should be repeated at three- to five-minute intervals and should be titrated to a reduction of secretions and to reduction of ventilatory resistance. When the intravenous preparation is available, the preferred route of atropine administration is via the intravenous route, but this route should be avoided until hypoxia is corrected, because intravenously administered atropine in hypoxic animals has produced ventricular fibrillation. In a hypotensive patient or a patient with poor veins, atropine might be given intratracheally, either via the endotracheal tube or directly into the trachea, for more rapid absorption via the peribronchial vessels. The medical care provider might err in giving too much atropine to a mild to moderate casualty. More importantly, the care provider might err by giving too little atropine to a severe casualty. In a severe casualty, atropine should be pushed at frequent intervals until secretions are dry (or nearly dry) and until ventilation can be accomplished with ease. In reported cases this has required 10 to 20 mg of atropine within the first several hours. A conscious, less-severely exposed casualty should receive atropine until he is breathing comfortably, and he will be able to communicate this. Dry secretions need not be an end point in mild to moderate casualties. The casualty with skin exposure to liquid is more difficult to evaluate and manage than is a casualty from vapor exposure. Agent on the surface of the skin can be decontaminated, but agent absorbed into the skin cannot be removed. The initial effects from absorbed liquid agent can start two to three hours after thorough decontamination of agent droplets on the skin. A casualty from liquid exposure on the skin may continue to worsen because of continued absorption of the agent from the skin depot. The first effects of a liquid droplet on the skin are sweating with or without blanching and occasionally with muscular fasciculations at the site. Gastrointestinal effects (nausea, vomiting, and sometimes diarrhea) are the first systemic effects, and these may start from 0.5 to 18 hours after contact with the agent. If these effects occur within the first several hours after exposure, they may portend more severe effects, and initial therapy should be two MARK I’s. If effects begin later, initial therapy should be one MARK I. A large amount of liquid agent on the skin will cause effects 1 to 30 minutes after contact, whether or not decontamination was done. Nevertheless, early decontamination may lessen the magnitude of the effects. After a one- to thirty-minute latent or asymptomatic period, the casualty will suddenly lose consciousness and begin seizure activity. The condition of the casualty and management are the same as described for a severe casualty from vapor exposure. Further care of the severe casualty consists of atropine administration to minimize secretions and of ventilation until spontaneous respiration resumes. Oxime administration should be repeated at hourly intervals for two or three additional doses. The preferred method of administration of the oxime is by intravenous drip of 1 gram over 20 to 30 minutes (more rapid administration will cause hypertension), but three additional oxime autoinjectors (total dose of 1.8 grams) may be given if the intravenous route cannot be used. The need for ventilation may continue for 0.5 to 3 hours. Unless prolonged hypoxia or other complications have occurred, the casualty will eventually begin having spontaneous muscular activity and make sporadic attempts to breathe. Muscles will become stronger and breathing more regular, and the casualty will have intermittent episodes of conscious behavior. Within an hour or two he will be breathing, moving, and conscious, although he will be weak and intermittently obtunded. Table III
NERVE AGENT EFFECTS
Vapor Exposure
Table IV
NERVE AGENT EFFECTS
Liquid on skin
Mild/moderate
Most of the nerve agents were originally produced in a search for insecticides, but because of their toxicity, they were evaluated for military use. Nerve agents have been used in wars and by terrorists. They are known to be stored by several nations, including the United States. What happens to nerve agents GA, GB, GD, and VX when they enter the environment? Nerve agents GA, GB, GD, and VX could enter the environment from an accidental release. The general population will not be exposed to nerve agents GA, GB, GD, or VX unless there is an accidental release from a military storage facility. Even in very small amounts, nerve agents are highly toxic if you inhale or swallow them, or if they come in contact with your skin or eyes. In general, the manifestation of toxic effects is faster if you inhale or swallow nerve agents than if they contact your skin. The initial effects also depend on the amount you are exposed to. The onset of mild to moderate effects after dermal exposure may be delayed for as long as 18 hours. Regardless of the route of exposure, the manifestation of nerve agent exposure includes runny nose, chest tightness, pinpoint pupils, shortness of breath, excessive salivation and sweating, nausea, vomiting, abdominal cramps, involuntary defecation and urination, muscle twitching, confusion, seizures, paralysis, coma, respiratory paralysis, and death. Incapacitating effects occur within 1 to 10 minutes and fatal effects can occur within 1 to 10 minutes for GA, GB, and GD, and within 4 to 18 hours for VX. Fatigue, irritability, nervousness, and memory defects may persist for as long as 6 weeks after recovery from an exposure episode. We do not know if exposure to the nerve agents GA, GB, GD, or VX might result in reproductive effects in humans. How likely are nerve agents GA, GB, GD, and VX to cause cancer? The Department of Heath and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified GA, GB, GD, and VX as to their carcinogenicity to humans. Limited data in animals indicate that nerve agents are not likely to be carcinogenic. How can nerve agents GA, GB, GD, and VX affect children? Children exposed to nerve agents are likely to experience the same toxic effects experienced by exposed adults. We do not know whether children differ from adults in their susceptibility to nerve agents. We do not know if exposure to the nerve agents GA, GB, GD, or VX might result in developmental effects in humans. How can families reduce the risk of exposure to nerve agents GA, GB, GD and VX? It is unlikely that the general population will be exposed to nerve agents. Is there a medical test to show whether I’ve been exposed to nerve agents GA, GB, GD, and VX? There are medical tests available to determine whether you have been exposed to nerve agents. There are tests to measure degradation products of nerve agents in the urine, but are not generally useful. A different kind of test measures the levels of a substance called cholinesterase in the blood. If these levels are less than half what they should be, and you were exposed to nerve gases, you may get symptoms of poisoning. Cholinesterase levels in the blood can stay low for months after you have been exposed to nerve agents. Measurement of cholinesterase levels in blood is not specific for exposure to nerve agents. |
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Facts About VXWhat VX is…..
Where VX is found and how it is used
How people can be exposed to VX
How VX works
Immediate signs and symptoms of VX exposure
What the long-term health effects are
How people can protect themselves, and what they should do if they are exposed to VX
How VX exposure is treated
How to get more information about VX
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