Postoperative Pneumonia: a Prospective Study of Risk Factors and Morbidity

Background: Postoperative pneumonia (PP) is a major complication that has been linked to microaspiration of pathogens originating in the gastrointestinal tract. This prospective study was performed to define the role of gastric bacterial aspiration in the development of PP.

Methods: Informed consent was obtained before operations from 140 veterans scheduled for major elective procedures requiring nasogastric tubes, and cultures were obtained of the gastric contents and sputum twice daily after operation.

Results: PP developed in 26 (18.6%) of 140 patients. The patients who had PP did not differ from those with no pneumonia after operation except for a history of chronic obstructive pulmonary disease, which was found in 38.5% of those with PP compared with 20% of patients with no pneumonia (p < 0.05). Morbidity was increased in association with PP, because length of stay in the surgical intensive care unit (6.2 vs 2.6 days), days intubated (2.7 vs 0.6), total postoperative days (15.3 vs 8.4), and mortality rates (19.2% vs 1.7%) were greater than in patients with no pneumonia. Gastric pathogens were present on entry in 38% of patients, and 32% of these had PP compared with 13% whose initial gastric cultures were sterile (p = 0.01). Colonization of sputum for greater than 24 hours with gastric pathogens occurred in 28% of patients. These patients had a 40% incidence of PP compared with 12% in patients without such evidence of microaspiration (p < 0.01).

Conclusions: PP is a morbid postoperative complication associated with not only chronic obstructive pulmonary disease but also the presence of gastric bacteria during operation and transmission of gastric bacteria to the pulmonary tree after operation.