The stomach should be empty before we give general anesthesia because regurgi-tating or vomiting and then, because of obtunded reflexes, inhaling the stuff found in the stomach can lead to serious trouble. The aspirated particulate matter can lodge in a distal bronchus, get infected, and result in bronchopneumonia or lung abscess. A large particle can block a mainstem bronchus or the trachea with obvi-ous dire consequences. Even in the OR, a patient can be treated with the Heimlich maneuver. Given an unconscious patient and the worry about more regurgita-tion and aspiration, tools such as a bronchoscope and suction available in the OR might be better suited for retrieval of foreign matter in the trachea or upper bronchial tree.
More common than particulate aspiration is the aspiration of gastric juice. If it has a pH under 2.5 and a volume of more than 0.4–1.0 mL/kg, the aspirate can cause the infamous Mendelson syndrome, a nasty chemical burn of the lungs that can be fatal. Treatment consists of support of ventilation, often with positive end expiratory pressure (PEEP) in order to expand the bronchioles and alveoli, reduce edema, and improve gas exchange.
The potential of gastric acid aspiration leads us to take precautions. The idea of emptying the stomach with help of a gastric tube comes to mind. While it might decompress a full stomach by removing gas and liquid, it cannot empty the stomach and is rather unkind in the awake patient. For elective surgery, we ask patients to take nothing by mouth for several hours before anesthesia. We also have drugs available to increase gastric pH and reduce volume as indicated. Even with such appropriate preparations, for patients with a full stomach or gastro-esophageal reflux disease (GERD), we would resort to a rapid sequence induction (see General anesthesia).
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