Predictors of intraoperative-acquired surgical wound infections

During a 4-year period, we collected prospective epidemiological data and intraoperative wound cultures from 1852 surgery patients at a university-affiliated community hospital in order to identify the critical risk factors for postoperative wound infections and study the impact of perioperative antibiotics on the bacteriology of infected wounds. Stepwise logistic regression analysis revealed four risk factors that were independent of each other and highly predictive for subsequent wound infection. These were the surgical wound class, American Society of Anesthesiology (ASA) physical status grouping, duration of surgery and results of intraoperative cultures. Addition of other variables to our model did not increase the predicted probability of infection. Even though patients with positive intraoperative cultures had an increased rate of infection, this information had limited clinical utility because of its low predictive value, high false-positive rate and poor concordance with isolates from infected wounds. Patients who had received perioperative antibiotics and who developed infections were frequently infected with organisms that were resistant to the perioperative drug regimen, compared with patients who had not received antibiotics.