Risk factors for nosocomial pneumonia after coronary artery bypass graft operations

We attempted to determine risk factors for nosocomial pneumonia in patients undergoing a coronary artery bypass graft operation. We reviewed the microbiology and medical records for any patient with a sputum culture who had undergone a coronary artery bypass graft operation in 1988 to identify patients with pneumonia according to a standard clinical definition. We found 19 cases of pneumonia through our initial review; complete medical records were found on 15 cases. Gram-negative bacilli predominated as the most common etiologic agent causing pneumonia in this cohort. There were no clusters noted. Mortality was 26.6%. Pneumonia occurred approximately 4 days after the operation. Thirty-six controls were randomly selected from patients undergoing coronary artery bypass graft operations in 1988. Logistic regression analysis revealed that a history of chronic obstructive lung disease, duration of more than 2 days of mechanical ventilation after operation but before diagnosis of pneumonia, and receipt of gastric acid inhibitors (antacids or H2-blockers) were independent risk factors for nosocomial pneumonia. Only the last risk factor was amenable to intervention at the time of operation.