Development and validation of a multifactorial risk index for predicting postoperative pneumonia after major noncardiac surgery

Background: Pneumonia is a common postoperative complication associated with substantial morbidity and mortality. Objective: To develop and validate a preoperative risk index for predicting postoperative pneumonia. Design: Prospective cohort study with outcome assessment based on chart review. Setting: 100 Veterans Affairs Medical Centers performing major surgery. Patients: The risk index was developed by using data on 160 805 patients undergoing major noncardiac surgery between I September 1997 and 31 August 1999 and was validated by using data on 155 266 patients undergoing surgery between 1 September 1995 and 31 August 1997. Patients with preoperative pneumonia, ventilator dependence, and pneumonia that developed after postoperative respiratory failure were excluded. Measurements: Postoperative pneumonia was defined by using the Centers for Disease Control and Prevention definition of nosocomial pneumonia. Results: A total of 2466 patients (1.5%) developed pneumonia, and the 30-day postoperative mortality rate was 21%. A postoperative pneumonia risk index was developed that included type of surgery (abdominal aortic aneurysm repair, thoracic, upper abdominal, neck, vascular, and neurosurgery), age, functional status, weight loss, chronic obstructive pulmonary disease, general anesthesia, impaired sensorium, cerebral vascular accident, blood urea nitrogen level, transfusion, emergency surgery, long-term steroid use, smoking, and alcohol use. Patients were divided into five risk classes by using risk index scores. Pneumonia rates were 0.2% among those with 0 to 15 risk points, 1.2% for those with 16 to 25 risk points, 4.0% for those with 26 to 40 risk points, 9.4% for those with 41 to 55 risk points, and 15.3% for those with more than 55 risk points. The C-statistic was 0.805 for the development cohort and 0.817 for the validation cohort. Conclusions: The postoperative pneumonia risk index identifies patients at risk for postoperative pneumonia and may be useful in guiding perioperative respiratory care.