Answer:

Clinically significant aspiration is a relatively rare complication of anesthesia. The reported incidence is 1 to 5 per 10,000 patients, although it is more common in certain situations, such as traumatic brain injury. About half of the cases of perioperative aspiration occur during induction of anesthesia. Although an emergency indication for surgery is a major risk factor for aspiration, the majority of cases occur during elective procedures. Increased gastric pressure, decreased lower esophageal sphincter tone, and blunted protective airway reflexes promote aspiration. Therefore, risk factors for aspiration include full stomach, pregnancy, bowel obstruction, gastroesophageal reflux, obesity, gastrointestinal motility disorders, and neurologic conditions. Airway manipulation in an unfasted patient or an inadequate depth of anesthesia may increase the risk of aspiration. Many anesthetics reduce lower and upper esophageal sphincter tone and diminish protective airway reflexes. The appropriate use of laryngeal mask airways does not increase the risk of aspiration, although it may induce gastroesophageal reflux. Certain surgical procedures such as laparoscopic insufflation of the abdomen and bowel manipulation are associated with increased rates of aspiration.

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