Effects

Choking agent poisoning results in the lungs filling with fluid (massive pulmonary edema). Exposure to very high concentrations may result in death within several hours; in most fatal cases pulmonary edema reaches a maximum in 12 hours followed by death in 24-48 hours. If the casualty survives, resolution commences within 48 hours and, in the absence of complicating infection, there may be little or no residual damage.

Signs and Symptoms

The presence or absence of these symptoms is of little value in immediate prognosis. Some casualties with severe coughs fail to develop serious lung injury, while others with little sign of early respiratory tract irritation develop fatal pulmonary edema.

A period follows during which abnormal chest signs are absent and the casualty may be symptom-free. This interval commonly lasts 2 to 24 hours but may be shorter. It is terminated by the signs and symptoms of pulmonary edema. These begin with cough (occasionally painful), difficulty breathing, rapid, shallow breathing and cyanosis. Nausea and vomiting may appear. As the edema progresses, discomfort, apprehension and difficulty breathing increase and frothy sputum develops.

The casualty may develop shock-like symptoms and pale, clammy skin, low blood pressure and feeble, rapid heartbeat. During the acute phase, casualties may have minimal signs and symptoms and prognosis should be guarded. Casualties may very rapidly develop severe pulmonary edema. If casualties survive more than 48 hours they usually recover.