Terminal aspiration of sterile acidic gastric contents and oropharyngeal secretions containing bacteria occurs frequently as an agonal event and is often observed at autopsy (395). Cough and gag reflexes are depressed at death, allowing agonal regurgitation into the airway (396). This is not necessarily a cause of death, but a sign that an individual is obtunded (36,209,333,396). Psychiatric and neurological disorders that lead to choking cause aspiration of vomit (397).
Aspiration of gastric contents is common in individuals with a decreased level of consciousness (drug overdose, anesthesia [395,397,398]). Critically ill patients are at risk (395). The supine position predisposes to gastroesophageal reflux (398). Reflux is enhanced by decreased gastric motility, which leads to retained gastric contents and stomach distension in critically ill individuals (395). The risk of aspiration is high after removal of an endotracheal tube because of the residual effects of sedative drugs, the presence of a nasogastric tube, swallowing dysfunction related to upper airway sensitivity, glottic injury, and laryngeal muscular dysfunction (395). Although a nasogastric tube is present, significant volumes of acid can still accumulate, depending on tube placement (398). The tube also passes through the esophageal sphincters, interfering with their function (398). Gastrostomy-tube and nasogastric-tube feeding offer no protection from aspiration of colonized oral secretions (395). Postoperative patients are more likely to aspirate when swallowing rather than when vomiting or regurgitating, and they are usually seated (397).
Aspiration can present with acute respiratory distress, but in many elderly patients, it is "silent" (395). Coughing can be a sign of acute aspiration (397). Mendelson's syndrome refers to the acute "autolytic" appearance of the lung as an immediate response to aspiration of acidic (pH <2.5) stomach contents (395,398). Microscopic examination reveals edema and foreign material in distal airways and alveoli (Fig. 59; refs. 350, 363, and 397). Eventual bacterial colonization occurs. If acute inflammation develops in response to bacteria (aspiration pneumonia), this indicates a survival period. If the pneumonia is extensive, then it is a cause of death (395,397). Inhalation of nonobstructing food particles can lead to a hemorrhagic pneumonia within hours (398). Within a few days, a granulomatous response is observed (see Subheading 3.5. and ref. 398). Diffuse alveolar damage also may follow (398). Inhalation of more basic (pH >2.5) liquid leads to pulmonary edema, which resolves rapidly with little lung damage and inflammation (398). Pulmonary edema occurs several hours after base aspiration, in contrast with acid aspiration (398). Passive transfer of gastric contents to the air passages does occur after death (396,397). Gastric contents were found in the air passages in about one-fourth of adult and pediatric deaths ("sudden infant deaths") in one study (396). Green discoloration of lung parenchyma may be observed (Fig. 59). At autopsy, green or brown material may be seen in the mainstem (usually right) or intraparenchymal bronchi (Fig. 60; refs. 337, 342, 377 and 389).
Toxicology is important to rule out incapacitation by alcohol and other drugs, particularly if there is no clearly defined cause of death (355).
Gastroesophageal reflux is one theory proposed to explain apnea leading to SIDS (35). The introduction of acid into the esophagus was also thought to cause cardiac arrhythmia (35,399). Studies have shown that most apneic episodes are independent of gastroesophageal reflux (399). Reflux is more likely to occur while the infant is awake rather than when the child is sleeping, the usual scenario in SIDS (399). Gastro-esophageal reflux may simply be a manifestation of general developmental delay (35). Reflux is less likely in the prone position, a risk factor for SIDS (ref. 400; see Subheading 3.1.3.).
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Gastroesophageal reflux disease is the medical term for what we know as acid reflux. Acid reflux occurs when the stomach releases its liquid back into the esophagus, causing inflammation and damage to the esophageal lining. The regurgitated acid most often consists of a few compoundsbr acid, bile, and pepsin.