The stomach
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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