If the exposure has been severe:

• The cardiovascular symptoms will dominate and twitching (which usually appears first in the eyelids and in the facial and calf muscles) becomes generalized.
• Many rippling movements are seen under the skin and twitching movements appear in all parts of the body.
• This is followed by severe generalized muscular weakness, including the muscles of respiration.
• The respiratory movements become more labored, shallow and rapid; then they become slow and fi nally intermittent.

After moderate or severe exposure:

• Excessive bronchial and upper airway secretions occur and may become very profuse, causing coughing, airway obstruction and respiratory distress.
• Bronchial secretion and salivation may be so profuse that watery secretions run out of the sides of the mouth. The secretions may be thick and tenacious.
• If the exposure is not so overwhelming as to cause death within a few minutes, other effects appear. These include sweating, anorexia, nausea and heartburn.

Severe exposure — High exposure to nerve agents may cause:

• Abdominal cramps
• Vomiting
• Diarrhea
• Frequent urination
• Profuse perspiration
• Involuntary defecation and urination
• Cardio respiratory arrest
• Death

The casualty may have changes in speech, consisting of slurring, difficulty in forming words, and multiple repetition of the last syllable.

The casualty may then become comatose, reflexes may disappear and generalized convulsions may ensue.

With the appearance of severe central nervous system (CNS) symptoms, central respiratory depression will occur and may progress to respiratory arrest.

After severe exposure the casualty may lose consciousness and convulse within a minute without other obvious symptoms.

Death is usually due to respiratory arrest. The casualty will require prompt initiation of assisted ventilation to prevent death. If assisted ventilation is initiated, the individual may survive several lethal doses of a nerve agent.

If the exposure has been overwhelming, amounting to many times the lethal dose, death may occur despite treatment due to respiratory arrest and cardiac arrhythmia. When overwhelming doses of the agent are absorbed quickly, death occurs rapidly without orderly progression of symptoms.

Nerve agent poisoning may be identified from the characteristic signs and symptoms. If exposure to vapor has occurred, the pupils will be very small, usually pin-pointed. If exposure has been cutaneous or has followed ingestion of a nerve agent in contaminated food or water, the pupils may be normal or, in the presence of severe systemic symptoms, slightly to moderately reduced in size. In this event, the other manifestations of nerve agent poisoning must be relied on to establish the diagnosis.

WARNING! No other known chemical agent produces muscular twitching, rapidly developing pin-point pupils (miosis), motor control and central nervous system collapse.

The rapid action of nerve agents calls for immediate self-treatment. Unexplained nasal secretion, salivation, tightness of the chest, shortness of breath, constriction of pupils, muscular twitching, or nausea and abdominal cramps call for the immediate intramuscular injection of 2 mg of atropine.