Postoperative pneumonia occurs in 9 to 40 percent of patients and has an associated mortality rate of 30 to 46 percent. Preoperative assessment of a patient's risk for postoperative pneumonia might encourage protective pre-operative respiratory preparation. Arozullah and colleagues performed a multicenter observational cohort study of patients undergoing major noncardiac surgery to determine easily obtainable preoperative risk factors for postoperative pneumonia.

Patients at 100 Veterans Affairs medical centers were used to develop and validate a risk index model. Of the 155,266 enrolled patients, 2,466 (1.5 percent) had postoperative pneumonia. These patients had a 30-day postoperative mortality rate of 21 percent compared with a mortality rate of 2 percent in patients without postoperative pneumonia. Postoperative pneumonia was more likely among patients undergoing abdominal aortic aneurysm repair; thoracic, upper abdominal, or neck surgery; neurosurgery; or peripheral vascular surgery.

A model was developed by assigning point values to risk factors and using the sum of the points to determine a risk class (see accompanying table). Risk class ranges are 1 (zero to 15 points), 2 (16 to 25 points), 3 (26 to 40 points), 4 (41 to 55 points), and 5 (more than 55 points). The postoperative pneumonia rate in each of these classes was similar in both the development and the validation cohort and was 0.24 percent, 1.20 percent, 4.0 percent, 9.4 percent, and 15.3 percent, respectively.

The authors conclude that the use of a postoperative pneumonia risk index for predicting pneumonia after major noncardiac surgery may encourage optimal perioperative testing and respiratory care in high-risk patients. The proposed risk index can be applied easily because it is based on readily obtainable information and results that require little specialized testing. Since the population in this study included only men, the benefit of the index must be confirmed in women.

In an accompanying editorial, Lawrence confirms the usefulness of preoperative risk stratification to encourage perioperative interventions that will decrease morbidity and mortality. It would be important to determine if prophylactic interventions based on risk stratifications really will be effective. More research is needed to make optimal use of risk assessment tools.