MOXIOUS GASES AflD FUMES



Exposure to toxic gases and fumes is an increas­ing problem in modern industrial society and may cause harm by four basic mechanisms (Table 27-1). Asphyxia occurs when the 02 in inspired air is displaced by another gas. The commonest mechanism of injury is local irritation, the form and extent of which depend on the concentration, solubility, and duration of exposure to the toxic gas. Highly soluble gases, such as ammonia, rap­idly injure the mucous membranes of the eye and upper airway, causing an intense burning pain in the eyes, nose, and throat, with lacrimation, rhinorrhea, and a sense of suffocation. This, com­bined with the strong pungent odor of ammonia, causes the victim to flee from the site of exposure. Lower airway injury is not observed unless the victim is trapped or a massive spill occurs, in posure to nitrogen dioxide is classically encountered in farmers, as large quantities of this gas’ are formed by fermentation during the first week after filling a silo pit. The victim typically presents with cough, dyspnea, bronchospasm, and weakness, with little evidence of ocular or upper airway irritation. After a lag of one or more hours there may be progression to frank pulmo­nary edema. Following recovery from the acute illness the patient may develop bronchiolitis ob­literans, characterized by progressive dyspnea. Absorption of a toxic gas with systemic conse­quences is best characterized by carbon monox­ide, as discussed under smoke inhalation. Expo­sure to isocyanate, platinum compounds, or formalin vapors may cause asthma, either im­mediate or delayed in onset, and is more fully dis­cussed in Chapter 19.

Management of exposure to a toxic gas is gen­erally supportive in nature. The victim should be removed from the source of exposure, and a patent airway with adequate ventilation should be en­sured. Correction of hypoxemia may be possible with supplemental 02, or intubation and me­chanical ventilation may be necessary. The pa­tient should be carefully monitored for a delayed reaction to the agent. Additional measures that may be required include bronchodilators and cor­rection of acid-base disturbance and shock. The role of prophylactic antibiotics and steroids re­mains undetermined, although a trial of steroids is usually employed in patients with bronchiolitis obliterans.