Most cases of witnessed or otherwise recent aspiration of oropharyngeal or gastric contents associated with a new pulmonary infiltrate represent an acute chemical pneumonitis rather than an infection. These cases usually resolve without antimicrobial therapy, with deep breathing and coughing, or with chest physiotherapy, when required. There is no convincing evidence that early administration of antimicrobials decreases subsequent incidences of complicating bacterial pneumonia, although there is evidence that such treatment may be associated with subsequent pneumonia caused by a relatively antimicrobial-resistant organism.
As soon as regurgitation is suspected, the patient should be placed in Trendelenberg position so that gastric contents drain out of the mouth instead of into the trachea. The pharynx and, if possible, the trachea should be thoroughly suctioned. The mainstay of therapy in patients who subsequently become hypoxic is positive-pressure ventilation. Intubation and the institution of positive end-expiratory pressure are often required. Bronchoscopy, pulmonary lavage, and (as above) broad-spectrum antibiotics are not indicated except possibly when particulate aspiration has occurred. The use of corticosteroids is generally not recommended.
Aspiration that has resulted in pneumonia, lung abscess, or empyema caused by oropharyngeal anaerobic bacteria has usually been treated, at least initially, with penicillin. However, in a critically ill patient with this syndrome, therapy should usually begin with penicillin 2 million U IV every 4 hours and metronidazole 750 mg IV every 6 hours or with clindamycin 900 mg every 8 hours. Aspiration can also be complicated by later development of aerobic acute bacterial pneumonia. Much less commonly, aspiration can produce an acute, rapidly progressive necrotizing pneumonia. This infection usually involves anaerobes and facultatively aerobic enteric gram-negative bacilli. The clinical context is often major aspiration in a patient without gastric acid (and therefore a large gastric bacterial population) or with an accumulation of feculent material in the stomach caused by adynamic ileus, upper GI bleeding, or bowel obstruction. Treatment must include adequate coverage for anaerobes, including Bacteroides fragilis, and aerobic gram-negative organisms. As in other acute gram-negative pneumonias, it is unwise to rely on an aminoglycoside alone for aerobic gram-negative coverage. Acceptable initial regimens include piperacillin/tazobactam 3.375 g IV every 6 hours with gentamicin 4.5 mg/kg every 24 hours, clindamycin 900 mg IV every 8 hours with cefotaxime 2 g IV every 6 hours, and meropenem 1 g every 8 hours with gentamicin 4.5 mg/kg IV every 24 hours. Ciprofloxacin can be substituted for the aminoglycoside when toxicity is a concern.