Pulmonary aspiration syndromes JEFFREY L. KAUFMAN, DD. JAMES C. GIUDICE, D.O., FCCP ROBERT GORDON, DD. Stratford, New Jersey is a change in function of the lower esophageal sphincter.4- 6 A change in the state of consciousness Aspiration of pharyngeal contents is as a result of an overdose of a sedative drug, general more common than aspiration of anesthesia, cerebrovascular accident, cardiopul- gastric contents, and three syndromes monary arrest, a seizure disorder, or alcoholic in- may result. Aspiration of gastric acid, toxication is the most common cause. The fre- of pathogenic bacteria, and of inert quency of aspiration problems is increased when a substances or particles cause different nasogastric tube or tracheostomy is present. clinical pictures, although in some In general, bacteria may reach the lung by any of instances they may be difficult to four routes: (1) aspiration, (2) inhalation, (3) differentiate. Since the three hematogenous spread, and (4) direct extension syndromes call for different from a contiguous site. In one study, 45 percent of management, it is important to normal subjects were noted to have aspirated identify the particular syndrome. The pharyngeal contents during sleep. Of patients with prognosis for aspiration of stomach a depressed sensorium, 70 percent aspirated phar- contents varies with the acidity. When yngeal contents. airway obstruction is due to aspiration By adding barium sulfate to beverages of of an inert object, the prognosis is ninety-four patients and placing barium in the excellent if obstruction is relieved stomach by tube in another fifty-one patients, quickly. Gardners demonstrated aspiration of pharyngeal contents into the lungs of ten of the first ninety-four patients and aspiration of gastric contents in only one of the second fifty-one patients. These were Pulmonary aspiration of gastric or pharyngeal con- hospitalized adult patients who were ambulatory tents leads to three distinct, though often related, and had undergone surgery or were debilitated for clinical syndromes. 1,2 Figure 1 illustrates the other reasons. These results suggested that aspira- etiologic mechanisms and the reasons for confusion tion of pharyngeal contents is relatively frequent in diagnosis, since overlapping of the three is often but atpiration of gastric contents is infrequent in a unavoidable, and a clearcut distinction based on relatively normal population. They emphasized the clinical and roentgenographic criteria often cannot assertion of Karetzky and Khans that vomiting is be made. Distinction among them is, however, im- not a prerequisite for aspiration pneumonia. perative, since the therapeutic and prognostic im- Pulmonary infections are relatively uncommon plications differ. The first syndrome is related to among normal subjects. Hence, aspiration of the aspiration of toxic fluids such as hydrochloric pharyngeal contents alone cannot be blamed for acid, and results in chemical pneumonitis. The sec- pleuropulmonary infection secondary to aspira- ond syndrome is related to the aspiration of bacter- tion. The type and amount of bacteria aspirated, ial pathogens and results in infection. The third defense mechanisms, and previous damage from syndrome is related to aspiration of relatively inert acid aspiration are among the other factors that substances and is associated with airway closure or contribute to the actual development of infection. obstruction.3 With respect to aspiration of gastric contents, the The three most common aspiration-related dis- pH of the aspirated material has prognostic eases are, then: aspiration of acid gastric contents significance. A critical pH of 2.5 below which se- with associated pneumonitis (Mendelsons syn- vere lung damage occurs has been suggested. drome), pleuropulmonary infection (aerobic or for human beings. Little damage occurs when the anaerobic), and airway obstruction.,4 These dis- pH is higher than this. The pulmonary pathologic eases may coexist or occur separately or sequen- changes following acid aspiration have been de- tially. scribed in detail. s, 12 13 The initial damage after acid aspiration is rapid; the acid burn occurs im- Pathogenesis mediately. The common factor in aspiration syndromes often When acid gastric juice containing methylene Pulmonary aspiration syndromes 542/97 cavity (empyema or bronchopleural fistula). Typically a patient will have malodorous putrid sputum and show cavitation on the chest radio- graph. 2 Clinically, the patient often is chronically ill, with low-grade fever and a radiographic pattern of infiltrates in lower lung zones, abscess forma- tion, or empyema. Diagnosis There are three methods of identification of the Fig. 1. Aspiration of contents into the lungs causes three syn dromes related to the three major aspirates—stomach acid, causative organism in aspiration pneumonia. Trans- bacteria, and inert substances. Some patients who aspirate tracheal aspiration and aspiration of empyema fluid acid or an inert substance experience infective complications. with aerobic and anaerobic cultures are perhaps TABLE 1. BACTERIOLOGY OF ASPIRATION PNEUMONIA. the preferable approaches. Culture of an organism Aerobes Anaerobes Both from blood would be highly suggestive in the proper Percent Percent Percent clinical milieu. Aspiration of sputum for culture Community acquired 10 60 30 from the nose, mouth, or endotracheal tube is not Hospital acquired 42 16 42 acceptable in a situation in which anaerobic bac- *Combine& data. t 11143 teria play an important role (Table 2). Community-acquired aspiration pneumonia is TABLE 2. COMMON ISOLATES IN ASPIRATION PNEUMONIA. due primarily to anaerobes, and normally more Aerobic Anaerobic than one anaerobe is recovered. Bacteroides fragil- Gram-positive cocci Cocci is with in vitro resistance to penicillin G is recov- Staphylococcus aureus Peptostreptococcus Streptococcus pneumoniae Microaerophilic ered in approximately 15 or 20 percent of cases. streptococcus Paradoxically, the condition responds to penicillin. Peptococcus Hospitalized patients with aspiration disease have Gram-negative bacilli Gram-negative bacilli Klebsiella Bacteroides species a greater probability of colonization with enteric Pseudomonas aeruginosa Fusobacterium nucleatum gram-negative bacteria, pseudomonas, or staphy- E. col i lococci and therefore the frequency of infections with aerobic bacteria is increased (Table 2). blue was instilled into dog lungs, the methylene blue was seen on the surface of the lung in from 12 Therapy to 18 seconds. 14 Areas of atelectasis were seen Antimicrobial therapy should be selected on the within 3 minutes. 14 Within 4 hours there is an basis of results of Gram staining and sputum cul- acute infiltration of polymorphonuclear cells and tures. However, a properly obtained sputum fibrin in the alveolar spaces; the lung becomes specimen demonstrating polymorphonuclear leu- boggy and edematous. After 72 hours resolution kocytes and a mixture of gram-positive cocci and has begun.5 rods, as well as pleomorphic gram-negative rods, when aerobic cultures show "normal flora" is Pleuropulmonary sepsis strongly suggestive of an anaerobic infection. With In most patients in whom pleuropulmonary infec- such a picture, therapy often is begun empiri- tions develop as a result of aspiration, bacteria are cally.2, 16-19 present in the oral flora. Patients in whom aspira- If material for culture cannot be obtained or tion disease occurs outside the hospital environ- while results are awaited, penicillin G is the drug of ment often have infection with anaerobic or- choice for aspiration pneumonia occurring outside ganisms, but those in whom it occurs after hospital- the hospital. Intravenous administration of ization for any length of time have an increased 1,200,000 units of penicillin every 6 hours is an risk of infection resulting from aerobic organisms acceptable dosage schedule for hospitalized pa- such as gram-negative bacilli or staphylococci 5,6, 15 tients. Partial resolution may be evident radio- (Table 1). The actual episode of aspiration may graphically in from 7 to 10 days, and at this time have gone unrecognized. There is some overlapping oral penicillin therapy can be begun. Treatment of syndromes; a patient may have had acid should be continued until there is complete resolu- pneumonitis before an infection develops. The tion, but certainly for at least 2 weeks for pneu- diagnosis of pleuropulmonary infection secondary monitis and 1 month for lung abscess. An amin- to aspiration must be suspected when a patient at oglycoside and penicillin are indicated when aspir- risk for aspiration has purulent sputum and radio- ation disease occurs within the hospital. When in- graphic changes in a dependent pulmonary lobe. dicated, clindamycin, cephalosporin, or a penicil- From 7 to 14 days after the aspiration of anaero- linase-resistant penicillin may be used instead of bic bacteria, tissue necrosis with abscess formation penicillin G. Clindamycin is an acceptable alterna- may occur, with direct extension into the pleural tive for patients with anaerobic sepsis who are al- 543/98 April 1981/Journal of AGA/vol. 80/no. 8 lergic to pencillin.Z 17-19 ma. Bronchoscopy for diagnosis should be per- formed soon after the suspected aspiration to avoid Chemical pneumonitis confusion due to mucosal changes resulting from Acid pneumonitis as a result of aspiration of gastric infection. contents is the prototype for chemical pneumonitis. The identification of food particles within the Occult aspiration