The triple threat of aspiration pneumonia.

A spiration pneumonia is a disease recognized since antiquity, yet there are few conditions in pulmonary medicine as frequent in occurrence but as lacking in consensus regarding classification and treatment. The priority for clinical description belongs to Hippocrates,’ the first scientific investigalion is ascribed to John Hunters in 1781, and the “classic study” is credited to Mendelson in 1946. Despite the plethora of reports in recent years, many physicians are confused by the variables in clinical descriptions and therapeutic recommendations. A major theme in the large collected case reports is that pulmonary complications of aspiration seldom occur in otherwise healthy persons. Thus, aspiration pneumonia is usually associated with an underlying disease. To define the clinical conditions associated with aspiration pneumonia, two sources of data can be employed. The first are reports of the incidence of this complication among all patients with specific diseases. For example, aspiration pneumonia has been incriminated as a leading cause of fatalities associated with anesthesia, ’5 head injuries,8 cerebrovascular accidents7 and debilitating diseases.8 Recurrent or chronic aspiration pneumonitis has been noted in 10-20 percent of patients with gastroesophageal reflux or achalasia.9 ’#{176} Another approach to understanding the clinical setting is to study all patients diagnosed as having aspiration pneumonia. In these reports, the principal underlying conditions are alcoholism, seizure disorders, cerebrovascular accidents, drug addiction, general anesthesia, esophageal disease and nasogastric tube feeding.”2#{176} These studies have defined the population at risk for developing aspiration pneumonia. Predisposing conditions are reduced levth of consciousness with consequent compromise of glottic closure and cough reflexes; dysphagia from neurologic or esophageal disorders; and mechanical dLs ruption of the “cardiac sphincter” due to nasogastric feeding tubes. The common denominator is a breakdown of normal protective mechanisms with subsequent entry of gastric secretions, oropharyngeal secretions or exogenous food or fluids into tracehobronchial passages. At the same time it must be recognized that aspiration into the lungs is common and is usually well tolerated. Several invesligators2123 have instilled dye into the stomach preoperatively, and then analyzed for the dye in the tracheobronchial tree during the operative procedure. The marker was detected in the tracheal aspirate in 7-16 percent of patients undergoing surgery, although pulmonary complications were seldom observed. In a similar experiment, Cameron et al demonstrated aspiralion of dye placed on the tongue in 69 percent of tracheostomized patients. This could not be conelated with progressive pulmonary disease. Additionally, Amberson noted that contrast material dropped into the mouths of sleeping patients was detected in the lung on x-ray films the following morning. Again, there were no ill-effects. These studies suggest that aspiration of gastric contents and oropharyngeal secretions is common, generally passing unrecognized with no sequellae. The decisive factor among patients who develop pulmonary complications is presumably related to the frequency, volume and character of the aspirate. There is an unfortunate tendency to combine the pulmonary complications of aspiration under a singl e banner, 1#{128} “aspiration pneumonia.” In fact, there are three distinct aspiration syndromes which are best categorized according to the nature of the inoculum ( Table 1 ). This classification determines the pathophysiologic mechanisms and dictates the therapeutic approach.