Risk factors for postoperative pneumonia.

Prospectively studied were 520 patients undergoing elective thoracic, upper abdominal and lower abdominal surgeries to analyze risk factors for postoperative pneumonias. Over-all, pneumonias developed in 91 of the 520 patients studied (17.5 percent). The acquisition of pneumonia was highly associated with preoperative markers of the severity of underlying diseases such as low serum albumin concentrations on admission (P less than 0.005) and high American Society of Anesthesiologists pre-anesthesia physical status classification (P less than 0.0001). History of smoking (P less than 0.001), longer preoperative stays (P less than 0.0001), longer operative procedures (P less than 0.0001) and thoracic or upper abdominal sites of surgery (P less than 0.0001) were also significant risk factors for postoperative pneumonias. Although massive obesity, old age and male sex were also associated with increased incidences of pneumonia, statistical significance was lost when these variables were controlled for site or duration of surgery. We were able to identify risk factors for pneumonia and to define a subpopulation of patients in which the risk of pneumonia was negligible. The acquisition of pneumonia by a low-risk patient should alert the physician to the possibility of a potentially preventable nosocomial infection.